Move tmk_core/common/<plat> (#13918)

19 files changed, 1905 insertions, 0 deletions

diff --git a/platforms/avr/_print.h b/platforms/avr/_print.h
new file mode 100644
index 000000000..5c1fdd26d
--- /dev/null
+++ b/platforms/avr/_print.h
@@ -0,0 +1,33 @@
+/* Copyright 2012 Jun Wako <wakojun@gmail.com> */
+/* Very basic print functions, intended to be used with usb_debug_only.c
+ * http://www.pjrc.com/teensy/
+ * Copyright (c) 2008 PJRC.COM, LLC
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+ * THE SOFTWARE.
+ */
+#pragma once
+
+#include "avr/xprintf.h"
+
+// Create user & normal print defines
+#define print(s) xputs(PSTR(s))
+#define println(s) xputs(PSTR(s "\r\n"))
+#define uprint(s) xputs(PSTR(s))
+#define uprintln(s) xputs(PSTR(s "\r\n"))
+#define uprintf(fmt, ...) __xprintf(PSTR(fmt), ##__VA_ARGS__)
\ No newline at end of file
diff --git a/platforms/avr/_timer.h b/platforms/avr/_timer.h
new file mode 100644
index 000000000..b81e0f68b
--- /dev/null
+++ b/platforms/avr/_timer.h
@@ -0,0 +1,19 @@
+/* Copyright 2021 Simon Arlott
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+#pragma once
+
+// The platform is 8-bit, so prefer 16-bit timers to reduce code size
+#define FAST_TIMER_T_SIZE 16
diff --git a/platforms/avr/_wait.h b/platforms/avr/_wait.h
new file mode 100644
index 000000000..683db6ae5
--- /dev/null
+++ b/platforms/avr/_wait.h
@@ -0,0 +1,49 @@
+/* Copyright 2021 QMK
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+#pragma once
+
+#include <util/delay.h>
+
+#define wait_ms(ms)                             \
+    do {                                        \
+        if (__builtin_constant_p(ms)) {         \
+            _delay_ms(ms);                      \
+        } else {                                \
+            for (uint16_t i = ms; i > 0; i--) { \
+                _delay_ms(1);                   \
+            }                                   \
+        }                                       \
+    } while (0)
+#define wait_us(us)                             \
+    do {                                        \
+        if (__builtin_constant_p(us)) {         \
+            _delay_us(us);                      \
+        } else {                                \
+            for (uint16_t i = us; i > 0; i--) { \
+                _delay_us(1);                   \
+            }                                   \
+        }                                       \
+    } while (0)
+#define wait_cpuclock(n) __builtin_avr_delay_cycles(n)
+#define CPU_CLOCK F_CPU
+
+/* The AVR series GPIOs have a one clock read delay for changes in the digital input signal.
+ * But here's more margin to make it two clocks. */
+#ifndef GPIO_INPUT_PIN_DELAY
+#    define GPIO_INPUT_PIN_DELAY 2
+#endif
+
+#define waitInputPinDelay() wait_cpuclock(GPIO_INPUT_PIN_DELAY)
diff --git a/platforms/avr/atomic_util.h b/platforms/avr/atomic_util.h
new file mode 100644
index 000000000..7c5d2e7dc
--- /dev/null
+++ b/platforms/avr/atomic_util.h
@@ -0,0 +1,22 @@
+/* Copyright 2021 QMK
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+#pragma once
+
+/* atomic macro for AVR */
+#include <util/atomic.h>
+
+#define ATOMIC_BLOCK_RESTORESTATE ATOMIC_BLOCK(ATOMIC_RESTORESTATE)
+#define ATOMIC_BLOCK_FORCEON ATOMIC_BLOCK(ATOMIC_FORCEON)
diff --git a/platforms/avr/bootloader.c b/platforms/avr/bootloader.c
new file mode 100644
index 000000000..c0272903b
--- /dev/null
+++ b/platforms/avr/bootloader.c
@@ -0,0 +1,293 @@
+#include <stdint.h>
+#include <stdbool.h>
+#include <avr/io.h>
+#include <avr/eeprom.h>
+#include <avr/interrupt.h>
+#include <avr/wdt.h>
+#include <util/delay.h>
+#include "bootloader.h"
+#include <avr/boot.h>
+
+#ifdef PROTOCOL_LUFA
+#    include <LUFA/Drivers/USB/USB.h>
+#endif
+
+/** \brief Bootloader Size in *bytes*
+ *
+ * AVR Boot section size are defined by setting BOOTSZ fuse in fact. Consult with your MCU datasheet.
+ * Note that 'Word'(2 bytes) size and address are used in datasheet while TMK uses 'Byte'.
+ *
+ * Size of Bootloaders in bytes:
+ *   Atmel DFU loader(ATmega32U4)   4096
+ *   Atmel DFU loader(AT90USB128)   8192
+ *   LUFA bootloader(ATmega32U4)    4096
+ *   Arduino Caterina(ATmega32U4)   4096
+ *   USBaspLoader(ATmega***)        2048
+ *   Teensy   halfKay(ATmega32U4)   512
+ *   Teensy++ halfKay(AT90USB128)   1024
+ *
+ * AVR Boot section is located at the end of Flash memory like the followings.
+ *
+ * byte     Atmel/LUFA(ATMega32u4)          byte     Atmel(AT90SUB128)
+ * 0x0000   +---------------+               0x00000  +---------------+
+ *          |               |                        |               |
+ *          |               |                        |               |
+ *          |  Application  |                        |  Application  |
+ *          |               |                        |               |
+ *          =               =                        =               =
+ *          |               | 32KB-4KB               |               | 128KB-8KB
+ * 0x7000   +---------------+               0x1E000  +---------------+
+ *          |  Bootloader   | 4KB                    |  Bootloader   | 8KB
+ * 0x7FFF   +---------------+               0x1FFFF  +---------------+
+ *
+ *
+ * byte     Teensy(ATMega32u4)              byte     Teensy++(AT90SUB128)
+ * 0x0000   +---------------+               0x00000  +---------------+
+ *          |               |                        |               |
+ *          |               |                        |               |
+ *          |  Application  |                        |  Application  |
+ *          |               |                        |               |
+ *          =               =                        =               =
+ *          |               | 32KB-512B              |               | 128KB-1KB
+ * 0x7E00   +---------------+               0x1FC00  +---------------+
+ *          |  Bootloader   | 512B                   |  Bootloader   | 1KB
+ * 0x7FFF   +---------------+               0x1FFFF  +---------------+
+ */
+#define FLASH_SIZE (FLASHEND + 1L)
+
+#if !defined(BOOTLOADER_SIZE)
+uint16_t bootloader_start;
+#endif
+
+// compatibility between ATMega8 and ATMega88
+#if !defined(MCUCSR)
+#    if defined(MCUSR)
+#        define MCUCSR MCUSR
+#    endif
+#endif
+
+/** \brief Entering the Bootloader via Software
+ *
+ * http://www.fourwalledcubicle.com/files/LUFA/Doc/120730/html/_page__software_bootloader_start.html
+ */
+#define BOOTLOADER_RESET_KEY 0xB007B007
+uint32_t reset_key __attribute__((section(".noinit,\"aw\",@nobits;")));
+
+/** \brief initialize MCU status by watchdog reset
+ *
+ * FIXME: needs doc
+ */
+__attribute__((weak)) void bootloader_jump(void) {
+#if !defined(BOOTLOADER_SIZE)
+    uint8_t high_fuse = boot_lock_fuse_bits_get(GET_HIGH_FUSE_BITS);
+
+    if (high_fuse & ~(FUSE_BOOTSZ0 & FUSE_BOOTSZ1)) {
+        bootloader_start = (FLASH_SIZE - 512) >> 1;
+    } else if (high_fuse & ~(FUSE_BOOTSZ1)) {
+        bootloader_start = (FLASH_SIZE - 1024) >> 1;
+    } else if (high_fuse & ~(FUSE_BOOTSZ0)) {
+        bootloader_start = (FLASH_SIZE - 2048) >> 1;
+    } else {
+        bootloader_start = (FLASH_SIZE - 4096) >> 1;
+    }
+#endif
+
+    // Something like this might work, but it compiled larger than the block above
+    // bootloader_start = FLASH_SIZE - (256 << (~high_fuse & 0b110 >> 1));
+
+#if defined(BOOTLOADER_HALFKAY)
+    //  http://www.pjrc.com/teensy/jump_to_bootloader.html
+    cli();
+    // disable watchdog, if enabled (it's not)
+    // disable all peripherals
+    // a shutdown call might make sense here
+    UDCON  = 1;
+    USBCON = (1 << FRZCLK);  // disable USB
+    UCSR1B = 0;
+    _delay_ms(5);
+#    if defined(__AVR_AT90USB162__)  // Teensy 1.0
+    EIMSK  = 0;
+    PCICR  = 0;
+    SPCR   = 0;
+    ACSR   = 0;
+    EECR   = 0;
+    TIMSK0 = 0;
+    TIMSK1 = 0;
+    UCSR1B = 0;
+    DDRB   = 0;
+    DDRC   = 0;
+    DDRD   = 0;
+    PORTB  = 0;
+    PORTC  = 0;
+    PORTD  = 0;
+    asm volatile("jmp 0x3E00");
+#    elif defined(__AVR_ATmega32U4__)   // Teensy 2.0
+    EIMSK  = 0;
+    PCICR  = 0;
+    SPCR   = 0;
+    ACSR   = 0;
+    EECR   = 0;
+    ADCSRA = 0;
+    TIMSK0 = 0;
+    TIMSK1 = 0;
+    TIMSK3 = 0;
+    TIMSK4 = 0;
+    UCSR1B = 0;
+    TWCR   = 0;
+    DDRB   = 0;
+    DDRC   = 0;
+    DDRD   = 0;
+    DDRE   = 0;
+    DDRF   = 0;
+    TWCR   = 0;
+    PORTB  = 0;
+    PORTC  = 0;
+    PORTD  = 0;
+    PORTE  = 0;
+    PORTF  = 0;
+    asm volatile("jmp 0x7E00");
+#    elif defined(__AVR_AT90USB646__)   // Teensy++ 1.0
+    EIMSK  = 0;
+    PCICR  = 0;
+    SPCR   = 0;
+    ACSR   = 0;
+    EECR   = 0;
+    ADCSRA = 0;
+    TIMSK0 = 0;
+    TIMSK1 = 0;
+    TIMSK2 = 0;
+    TIMSK3 = 0;
+    UCSR1B = 0;
+    TWCR   = 0;
+    DDRA   = 0;
+    DDRB   = 0;
+    DDRC   = 0;
+    DDRD   = 0;
+    DDRE   = 0;
+    DDRF   = 0;
+    PORTA  = 0;
+    PORTB  = 0;
+    PORTC  = 0;
+    PORTD  = 0;
+    PORTE  = 0;
+    PORTF  = 0;
+    asm volatile("jmp 0xFC00");
+#    elif defined(__AVR_AT90USB1286__)  // Teensy++ 2.0
+    EIMSK  = 0;
+    PCICR  = 0;
+    SPCR   = 0;
+    ACSR   = 0;
+    EECR   = 0;
+    ADCSRA = 0;
+    TIMSK0 = 0;
+    TIMSK1 = 0;
+    TIMSK2 = 0;
+    TIMSK3 = 0;
+    UCSR1B = 0;
+    TWCR   = 0;
+    DDRA   = 0;
+    DDRB   = 0;
+    DDRC   = 0;
+    DDRD   = 0;
+    DDRE   = 0;
+    DDRF   = 0;
+    PORTA  = 0;
+    PORTB  = 0;
+    PORTC  = 0;
+    PORTD  = 0;
+    PORTE  = 0;
+    PORTF  = 0;
+    asm volatile("jmp 0x1FC00");
+#    endif
+
+#elif defined(BOOTLOADER_CATERINA)
+    // this block may be optional
+    // TODO: figure it out
+
+    uint16_t *const bootKeyPtr = (uint16_t *)0x0800;
+
+    // Value used by Caterina bootloader use to determine whether to run the
+    // sketch or the bootloader programmer.
+    uint16_t bootKey = 0x7777;
+
+    *bootKeyPtr = bootKey;
+
+    // setup watchdog timeout
+    wdt_enable(WDTO_60MS);
+
+    while (1) {
+    }  // wait for watchdog timer to trigger
+
+#elif defined(BOOTLOADER_USBASP)
+    // Taken with permission of Stephan Baerwolf from https://github.com/tinyusbboard/API/blob/master/apipage.c
+    wdt_enable(WDTO_15MS);
+    wdt_reset();
+    asm volatile("cli                    \n\t"
+                 "ldi    r29 ,       %[ramendhi] \n\t"
+                 "ldi    r28 ,       %[ramendlo] \n\t"
+#    if (FLASHEND > 131071)
+                 "ldi    r18 ,       %[bootaddrhi]   \n\t"
+                 "st     Y+,         r18     \n\t"
+#    endif
+                 "ldi    r18 ,       %[bootaddrme]   \n\t"
+                 "st     Y+,     r18     \n\t"
+                 "ldi    r18 ,       %[bootaddrlo]   \n\t"
+                 "st     Y+,     r18     \n\t"
+                 "out    %[mcucsrio],    __zero_reg__    \n\t"
+                 "bootloader_startup_loop%=:         \n\t"
+                 "rjmp bootloader_startup_loop%=     \n\t"
+                 :
+                 : [mcucsrio] "I"(_SFR_IO_ADDR(MCUCSR)),
+#    if (FLASHEND > 131071)
+                   [ramendhi] "M"(((RAMEND - 2) >> 8) & 0xff), [ramendlo] "M"(((RAMEND - 2) >> 0) & 0xff), [bootaddrhi] "M"((((FLASH_SIZE - BOOTLOADER_SIZE) >> 1) >> 16) & 0xff),
+#    else
+                   [ramendhi] "M"(((RAMEND - 1) >> 8) & 0xff), [ramendlo] "M"(((RAMEND - 1) >> 0) & 0xff),
+#    endif
+                   [bootaddrme] "M"((((FLASH_SIZE - BOOTLOADER_SIZE) >> 1) >> 8) & 0xff), [bootaddrlo] "M"((((FLASH_SIZE - BOOTLOADER_SIZE) >> 1) >> 0) & 0xff));
+
+#else  // Assume remaining boards are DFU, even if the flag isn't set
+
+#    if !(defined(__AVR_ATmega32A__) || defined(__AVR_ATmega328P__) || defined(__AVR_ATmega328__) || defined(__AVR_ATtiny85__))  // no USB - maybe BOOTLOADER_BOOTLOADHID instead though?
+    UDCON  = 1;
+    USBCON = (1 << FRZCLK);  // disable USB
+    UCSR1B = 0;
+    _delay_ms(5);  // 5 seems to work fine
+#    endif
+
+#    ifdef BOOTLOADER_BOOTLOADHID
+    // force bootloadHID to stay in bootloader mode, so that it waits
+    // for a new firmware to be flashed
+    eeprom_write_byte((uint8_t *)1, 0x00);
+#    endif
+
+    // watchdog reset
+    reset_key = BOOTLOADER_RESET_KEY;
+    wdt_enable(WDTO_250MS);
+    for (;;)
+        ;
+#endif
+}
+
+/* this runs before main() */
+void bootloader_jump_after_watchdog_reset(void) __attribute__((used, naked, section(".init3")));
+void bootloader_jump_after_watchdog_reset(void) {
+#ifndef BOOTLOADER_HALFKAY
+    if ((MCUCSR & (1 << WDRF)) && reset_key == BOOTLOADER_RESET_KEY) {
+        reset_key = 0;
+
+        // My custom USBasploader requires this to come up.
+        MCUCSR = 0;
+
+        // Seems like Teensy halfkay loader requires clearing WDRF and disabling watchdog.
+        MCUCSR &= ~(1 << WDRF);
+        wdt_disable();
+
+// This is compled into 'icall', address should be in word unit, not byte.
+#    ifdef BOOTLOADER_SIZE
+        ((void (*)(void))((FLASH_SIZE - BOOTLOADER_SIZE) >> 1))();
+#    else
+        asm("ijmp" ::"z"(bootloader_start));
+#    endif
+    }
+#endif
+}
diff --git a/platforms/avr/bootloader_size.c b/platforms/avr/bootloader_size.c
new file mode 100644
index 000000000..a029f9321
--- /dev/null
+++ b/platforms/avr/bootloader_size.c
@@ -0,0 +1,21 @@
+// Copyright 2017 Jack Humbert
+//
+// This program is free software: you can redistribute it and/or modify
+// it under the terms of the GNU General Public License as published by
+// the Free Software Foundation, either version 2 of the License, or
+// (at your option) any later version.
+//
+// This program is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+//
+// You should have received a copy of the GNU General Public License
+// along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+#include <avr/io.h>
+#include <avr/boot.h>
+
+// clang-format off
+// this is not valid C - it's for computing the size available on the chip
+AVR_SIZE: FLASHEND + 1 - BOOTLOADER_SIZE
diff --git a/platforms/avr/gpio.h b/platforms/avr/gpio.h
new file mode 100644
index 000000000..e9be68491
--- /dev/null
+++ b/platforms/avr/gpio.h
@@ -0,0 +1,49 @@
+/* Copyright 2021 QMK
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+#pragma once
+
+#include <avr/io.h>
+#include "pin_defs.h"
+
+typedef uint8_t pin_t;
+
+/* Operation of GPIO by pin. */
+
+#define setPinInput(pin) (DDRx_ADDRESS(pin) &= ~_BV((pin)&0xF), PORTx_ADDRESS(pin) &= ~_BV((pin)&0xF))
+#define setPinInputHigh(pin) (DDRx_ADDRESS(pin) &= ~_BV((pin)&0xF), PORTx_ADDRESS(pin) |= _BV((pin)&0xF))
+#define setPinInputLow(pin) _Static_assert(0, "AVR processors cannot implement an input as pull low")
+#define setPinOutput(pin) (DDRx_ADDRESS(pin) |= _BV((pin)&0xF))
+
+#define writePinHigh(pin) (PORTx_ADDRESS(pin) |= _BV((pin)&0xF))
+#define writePinLow(pin) (PORTx_ADDRESS(pin) &= ~_BV((pin)&0xF))
+#define writePin(pin, level) ((level) ? writePinHigh(pin) : writePinLow(pin))
+
+#define readPin(pin) ((bool)(PINx_ADDRESS(pin) & _BV((pin)&0xF)))
+
+#define togglePin(pin) (PORTx_ADDRESS(pin) ^= _BV((pin)&0xF))
+
+/* Operation of GPIO by port. */
+
+typedef uint8_t port_data_t;
+
+#define readPort(port) PINx_ADDRESS(port)
+
+#define setPortBitInput(port, bit) (DDRx_ADDRESS(port) &= ~_BV((bit)&0xF), PORTx_ADDRESS(port) &= ~_BV((bit)&0xF))
+#define setPortBitInputHigh(port, bit) (DDRx_ADDRESS(port) &= ~_BV((bit)&0xF), PORTx_ADDRESS(port) |= _BV((bit)&0xF))
+#define setPortBitOutput(port, bit) (DDRx_ADDRESS(port) |= _BV((bit)&0xF))
+
+#define writePortBitLow(port, bit) (PORTx_ADDRESS(port) &= ~_BV((bit)&0xF))
+#define writePortBitHigh(port, bit) (PORTx_ADDRESS(port) |= _BV((bit)&0xF))
diff --git a/platforms/avr/pin_defs.h b/platforms/avr/pin_defs.h
new file mode 100644
index 000000000..23d948041
--- /dev/null
+++ b/platforms/avr/pin_defs.h
@@ -0,0 +1,128 @@
+/* Copyright 2021 QMK
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+#pragma once
+
+#include <avr/io.h>
+
+#define PORT_SHIFTER 4  // this may be 4 for all AVR chips
+
+// If you want to add more to this list, reference the PINx definitions in these header
+// files: https://github.com/vancegroup-mirrors/avr-libc/tree/master/avr-libc/include/avr
+
+#if defined(__AVR_ATmega32U4__) || defined(__AVR_ATmega16U4__)
+#    define ADDRESS_BASE 0x00
+#    define PINB_ADDRESS 0x3
+#    define PINC_ADDRESS 0x6
+#    define PIND_ADDRESS 0x9
+#    define PINE_ADDRESS 0xC
+#    define PINF_ADDRESS 0xF
+#elif defined(__AVR_AT90USB162__) || defined(__AVR_ATmega32U2__) || defined(__AVR_ATmega16U2__) || defined(__AVR_ATmega328P__) || defined(__AVR_ATmega328__)
+#    define ADDRESS_BASE 0x00
+#    define PINB_ADDRESS 0x3
+#    define PINC_ADDRESS 0x6
+#    define PIND_ADDRESS 0x9
+#elif defined(__AVR_AT90USB646__) || defined(__AVR_AT90USB647__) || defined(__AVR_AT90USB1286__) || defined(__AVR_AT90USB1287__)
+#    define ADDRESS_BASE 0x00
+#    define PINA_ADDRESS 0x0
+#    define PINB_ADDRESS 0x3
+#    define PINC_ADDRESS 0x6
+#    define PIND_ADDRESS 0x9
+#    define PINE_ADDRESS 0xC
+#    define PINF_ADDRESS 0xF
+#elif defined(__AVR_ATmega32A__)
+#    define ADDRESS_BASE 0x10
+#    define PIND_ADDRESS 0x0
+#    define PINC_ADDRESS 0x3
+#    define PINB_ADDRESS 0x6
+#    define PINA_ADDRESS 0x9
+#elif defined(__AVR_ATtiny85__)
+#    define ADDRESS_BASE 0x10
+#    define PINB_ADDRESS 0x6
+#else
+#    error "Pins are not defined"
+#endif
+
+#define PINDEF(port, pin) ((PIN##port##_ADDRESS << PORT_SHIFTER) | pin)
+
+#define _PIN_ADDRESS(p, offset) _SFR_IO8(ADDRESS_BASE + ((p) >> PORT_SHIFTER) + (offset))
+// Port X Input Pins Address
+#define PINx_ADDRESS(p) _PIN_ADDRESS(p, 0)
+// Port X Data Direction Register,  0:input 1:output
+#define DDRx_ADDRESS(p) _PIN_ADDRESS(p, 1)
+// Port X Data Register
+#define PORTx_ADDRESS(p) _PIN_ADDRESS(p, 2)
+
+/* I/O pins */
+#ifdef PORTA
+#    define A0 PINDEF(A, 0)
+#    define A1 PINDEF(A, 1)
+#    define A2 PINDEF(A, 2)
+#    define A3 PINDEF(A, 3)
+#    define A4 PINDEF(A, 4)
+#    define A5 PINDEF(A, 5)
+#    define A6 PINDEF(A, 6)
+#    define A7 PINDEF(A, 7)
+#endif
+#ifdef PORTB
+#    define B0 PINDEF(B, 0)
+#    define B1 PINDEF(B, 1)
+#    define B2 PINDEF(B, 2)
+#    define B3 PINDEF(B, 3)
+#    define B4 PINDEF(B, 4)
+#    define B5 PINDEF(B, 5)
+#    define B6 PINDEF(B, 6)
+#    define B7 PINDEF(B, 7)
+#endif
+#ifdef PORTC
+#    define C0 PINDEF(C, 0)
+#    define C1 PINDEF(C, 1)
+#    define C2 PINDEF(C, 2)
+#    define C3 PINDEF(C, 3)
+#    define C4 PINDEF(C, 4)
+#    define C5 PINDEF(C, 5)
+#    define C6 PINDEF(C, 6)
+#    define C7 PINDEF(C, 7)
+#endif
+#ifdef PORTD
+#    define D0 PINDEF(D, 0)
+#    define D1 PINDEF(D, 1)
+#    define D2 PINDEF(D, 2)
+#    define D3 PINDEF(D, 3)
+#    define D4 PINDEF(D, 4)
+#    define D5 PINDEF(D, 5)
+#    define D6 PINDEF(D, 6)
+#    define D7 PINDEF(D, 7)
+#endif
+#ifdef PORTE
+#    define E0 PINDEF(E, 0)
+#    define E1 PINDEF(E, 1)
+#    define E2 PINDEF(E, 2)
+#    define E3 PINDEF(E, 3)
+#    define E4 PINDEF(E, 4)
+#    define E5 PINDEF(E, 5)
+#    define E6 PINDEF(E, 6)
+#    define E7 PINDEF(E, 7)
+#endif
+#ifdef PORTF
+#    define F0 PINDEF(F, 0)
+#    define F1 PINDEF(F, 1)
+#    define F2 PINDEF(F, 2)
+#    define F3 PINDEF(F, 3)
+#    define F4 PINDEF(F, 4)
+#    define F5 PINDEF(F, 5)
+#    define F6 PINDEF(F, 6)
+#    define F7 PINDEF(F, 7)
+#endif
diff --git a/platforms/avr/platform.c b/platforms/avr/platform.c
new file mode 100644
index 000000000..3e35b4fe4
--- /dev/null
+++ b/platforms/avr/platform.c
@@ -0,0 +1,21 @@
+/* Copyright 2021 QMK
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#include "platform_deps.h"
+
+void platform_setup(void) {
+    // do nothing
+}
diff --git a/platforms/avr/platform.mk b/platforms/avr/platform.mk
new file mode 100644
index 000000000..b45108736
--- /dev/null
+++ b/platforms/avr/platform.mk
@@ -0,0 +1,179 @@
+# Hey Emacs, this is a -*- makefile -*-
+##############################################################################
+# Compiler settings
+#
+CC = $(CC_PREFIX) avr-gcc
+OBJCOPY = avr-objcopy
+OBJDUMP = avr-objdump
+SIZE = avr-size
+AR = avr-ar
+NM = avr-nm
+HEX = $(OBJCOPY) -O $(FORMAT) -R .eeprom -R .fuse -R .lock -R .signature
+EEP = $(OBJCOPY) -j .eeprom --set-section-flags=.eeprom="alloc,load" --change-section-lma .eeprom=0 --no-change-warnings -O $(FORMAT)
+BIN =
+
+COMPILEFLAGS += -funsigned-char
+COMPILEFLAGS += -funsigned-bitfields
+COMPILEFLAGS += -ffunction-sections
+COMPILEFLAGS += -fdata-sections
+COMPILEFLAGS += -fpack-struct
+COMPILEFLAGS += -fshort-enums
+
+ASFLAGS += $(AVR_ASFLAGS)
+
+CFLAGS += $(COMPILEFLAGS) $(AVR_CFLAGS)
+CFLAGS += -fno-inline-small-functions
+CFLAGS += -fno-strict-aliasing
+
+CXXFLAGS += $(COMPILEFLAGS)
+CXXFLAGS += -fno-exceptions -std=c++11
+
+LDFLAGS +=-Wl,--gc-sections
+
+OPT_DEFS += -DF_CPU=$(F_CPU)UL
+
+MCUFLAGS = -mmcu=$(MCU)
+
+# List any extra directories to look for libraries here.
+#     Each directory must be seperated by a space.
+#     Use forward slashes for directory separators.
+#     For a directory that has spaces, enclose it in quotes.
+EXTRALIBDIRS =
+
+
+#---------------- External Memory Options ----------------
+
+# 64 KB of external RAM, starting after internal RAM (ATmega128!),
+# used for variables (.data/.bss) and heap (malloc()).
+#EXTMEMOPTS = -Wl,-Tdata=0x801100,--defsym=__heap_end=0x80ffff
+
+# 64 KB of external RAM, starting after internal RAM (ATmega128!),
+# only used for heap (malloc()).
+#EXTMEMOPTS = -Wl,--section-start,.data=0x801100,--defsym=__heap_end=0x80ffff
+
+EXTMEMOPTS =
+
+#---------------- Debugging Options ----------------
+
+# Debugging format.
+#     Native formats for AVR-GCC's -g are dwarf-2 [default] or stabs.
+#     AVR Studio 4.10 requires dwarf-2.
+#     AVR [Extended] COFF format requires stabs, plus an avr-objcopy run.
+DEBUG = dwarf-2
+
+# For simulavr only - target MCU frequency.
+DEBUG_MFREQ = $(F_CPU)
+
+# Set the DEBUG_UI to either gdb or insight.
+# DEBUG_UI = gdb
+DEBUG_UI = insight
+
+# Set the debugging back-end to either avarice, simulavr.
+DEBUG_BACKEND = avarice
+#DEBUG_BACKEND = simulavr
+
+# GDB Init Filename.
+GDBINIT_FILE = __avr_gdbinit
+
+# When using avarice settings for the JTAG
+JTAG_DEV = /dev/com1
+
+# Debugging port used to communicate between GDB / avarice / simulavr.
+DEBUG_PORT = 4242
+
+# Debugging host used to communicate between GDB / avarice / simulavr, normally
+#     just set to localhost unless doing some sort of crazy debugging when
+#     avarice is running on a different computer.
+DEBUG_HOST = localhost
+
+#============================================================================
+
+# Convert hex to bin.
+bin: $(BUILD_DIR)/$(TARGET).hex
+ifeq ($(BOOTLOADER),lufa-ms)
+        $(eval BIN_PADDING=$(shell n=`expr 32768 - $(BOOTLOADER_SIZE)` && echo $$(($$n)) || echo 0))
+        $(OBJCOPY) -Iihex -Obinary $(BUILD_DIR)/$(TARGET).hex $(BUILD_DIR)/$(TARGET).bin --pad-to $(BIN_PADDING)
+else
+        $(OBJCOPY) -Iihex -Obinary $(BUILD_DIR)/$(TARGET).hex $(BUILD_DIR)/$(TARGET).bin
+endif
+        $(COPY) $(BUILD_DIR)/$(TARGET).bin $(TARGET).bin;
+
+# copy bin to FLASH.bin
+flashbin: bin
+        $(COPY) $(BUILD_DIR)/$(TARGET).bin FLASH.bin;
+
+# Generate avr-gdb config/init file which does the following:
+#     define the reset signal, load the target file, connect to target, and set
+#     a breakpoint at main().
+gdb-config:
+        @$(REMOVE) $(GDBINIT_FILE)
+        @echo define reset >> $(GDBINIT_FILE)
+        @echo SIGNAL SIGHUP >> $(GDBINIT_FILE)
+        @echo end >> $(GDBINIT_FILE)
+        @echo file $(BUILD_DIR)/$(TARGET).elf >> $(GDBINIT_FILE)
+        @echo target remote $(DEBUG_HOST):$(DEBUG_PORT)  >> $(GDBINIT_FILE)
+ifeq ($(DEBUG_BACKEND),simulavr)
+        @echo load  >> $(GDBINIT_FILE)
+endif
+        @echo break main >> $(GDBINIT_FILE)
+
+debug: gdb-config $(BUILD_DIR)/$(TARGET).elf
+ifeq ($(DEBUG_BACKEND), avarice)
+        @echo Starting AVaRICE - Press enter when "waiting to connect" message displays.
+        @$(WINSHELL) /c start avarice --jtag $(JTAG_DEV) --erase --program --file \
+        $(BUILD_DIR)/$(TARGET).elf $(DEBUG_HOST):$(DEBUG_PORT)
+        @$(WINSHELL) /c pause
+
+else
+        @$(WINSHELL) /c start simulavr --gdbserver --device $(MCU) --clock-freq \
+        $(DEBUG_MFREQ) --port $(DEBUG_PORT)
+endif
+        @$(WINSHELL) /c start avr-$(DEBUG_UI) --command=$(GDBINIT_FILE)
+
+
+
+
+# Convert ELF to COFF for use in debugging / simulating in AVR Studio or VMLAB.
+COFFCONVERT = $(OBJCOPY) --debugging
+COFFCONVERT += --change-section-address .data-0x800000
+COFFCONVERT += --change-section-address .bss-0x800000
+COFFCONVERT += --change-section-address .noinit-0x800000
+COFFCONVERT += --change-section-address .eeprom-0x810000
+
+
+
+coff: $(BUILD_DIR)/$(TARGET).elf
+        @$(SECHO) $(MSG_COFF) $(BUILD_DIR)/$(TARGET).cof
+        $(COFFCONVERT) -O coff-avr $< $(BUILD_DIR)/$(TARGET).cof
+
+
+extcoff: $(BUILD_DIR)/$(TARGET).elf
+        @$(SECHO) $(MSG_EXTENDED_COFF) $(BUILD_DIR)/$(TARGET).cof
+        $(COFFCONVERT) -O coff-ext-avr $< $(BUILD_DIR)/$(TARGET).cof
+
+ifeq ($(strip $(BOOTLOADER)), qmk-dfu)
+QMK_BOOTLOADER_TYPE = DFU
+else ifeq ($(strip $(BOOTLOADER)), qmk-hid)
+QMK_BOOTLOADER_TYPE = HID
+endif
+
+bootloader:
+ifeq ($(strip $(QMK_BOOTLOADER_TYPE)),)
+        $(error Please set BOOTLOADER to "qmk-dfu" or "qmk-hid" first!)
+else
+        make -C lib/lufa/Bootloaders/$(QMK_BOOTLOADER_TYPE)/ clean
+        $(QMK_BIN) generate-dfu-header --quiet --keyboard $(KEYBOARD) --output lib/lufa/Bootloaders/$(QMK_BOOTLOADER_TYPE)/Keyboard.h
+        $(eval MAX_SIZE=$(shell n=`$(CC) -E -mmcu=$(MCU) -D__ASSEMBLER__ $(CFLAGS) $(OPT_DEFS) platforms/avr/bootloader_size.c 2> /dev/null | sed -ne 's/\r//;/^#/n;/^AVR_SIZE:/,$${s/^AVR_SIZE: //;p;}'` && echo $$(($$n)) || echo 0))
+        $(eval PROGRAM_SIZE_KB=$(shell n=`expr $(MAX_SIZE) / 1024` && echo $$(($$n)) || echo 0))
+        $(eval BOOT_SECTION_SIZE_KB=$(shell n=`expr  $(BOOTLOADER_SIZE) / 1024` && echo $$(($$n)) || echo 0))
+        $(eval FLASH_SIZE_KB=$(shell n=`expr $(PROGRAM_SIZE_KB) + $(BOOT_SECTION_SIZE_KB)` && echo $$(($$n)) || echo 0))
+        make -C lib/lufa/Bootloaders/$(QMK_BOOTLOADER_TYPE)/ MCU=$(MCU) ARCH=$(ARCH) F_CPU=$(F_CPU) FLASH_SIZE_KB=$(FLASH_SIZE_KB) BOOT_SECTION_SIZE_KB=$(BOOT_SECTION_SIZE_KB)
+        printf "Bootloader$(QMK_BOOTLOADER_TYPE).hex copied to $(TARGET)_bootloader.hex\n"
+        cp lib/lufa/Bootloaders/$(QMK_BOOTLOADER_TYPE)/Bootloader$(QMK_BOOTLOADER_TYPE).hex $(TARGET)_bootloader.hex
+endif
+
+production: $(BUILD_DIR)/$(TARGET).hex bootloader cpfirmware
+        @cat $(BUILD_DIR)/$(TARGET).hex | awk '/^:00000001FF/ == 0' > $(TARGET)_production.hex
+        @cat $(TARGET)_bootloader.hex >> $(TARGET)_production.hex
+        echo "File sizes:"
+        $(SIZE) $(TARGET).hex $(TARGET)_bootloader.hex $(TARGET)_production.hex
diff --git a/platforms/avr/platform_deps.h b/platforms/avr/platform_deps.h
new file mode 100644
index 000000000..45d9dcebf
--- /dev/null
+++ b/platforms/avr/platform_deps.h
@@ -0,0 +1,20 @@
+/* Copyright 2021 QMK
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+#pragma once
+
+#include <avr/pgmspace.h>
+#include <avr/io.h>
+#include <avr/interrupt.h>
diff --git a/platforms/avr/printf.c b/platforms/avr/printf.c
new file mode 100644
index 000000000..9ad7a3869
--- /dev/null
+++ b/platforms/avr/printf.c
@@ -0,0 +1,20 @@
+/*
+Copyright 2011 Jun Wako <wakojun@gmail.com>
+
+This program is free software: you can redistribute it and/or modify
+it under the terms of the GNU General Public License as published by
+the Free Software Foundation, either version 2 of the License, or
+(at your option) any later version.
+
+This program is distributed in the hope that it will be useful,
+but WITHOUT ANY WARRANTY; without even the implied warranty of
+MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+GNU General Public License for more details.
+
+You should have received a copy of the GNU General Public License
+along with this program.  If not, see <http://www.gnu.org/licenses/>.
+*/
+#include "xprintf.h"
+#include "sendchar.h"
+
+void print_set_sendchar(sendchar_func_t func) { xdev_out(func); }
diff --git a/platforms/avr/printf.mk b/platforms/avr/printf.mk
new file mode 100644
index 000000000..060ad88c5
--- /dev/null
+++ b/platforms/avr/printf.mk
@@ -0,0 +1,2 @@
+TMK_COMMON_SRC += $(PLATFORM_COMMON_DIR)/xprintf.S
+TMK_COMMON_SRC += $(PLATFORM_COMMON_DIR)/printf.c
diff --git a/platforms/avr/sleep_led.c b/platforms/avr/sleep_led.c
new file mode 100644
index 000000000..9a3b52abe
--- /dev/null
+++ b/platforms/avr/sleep_led.c
@@ -0,0 +1,124 @@
+#include <stdint.h>
+#include <avr/io.h>
+#include <avr/interrupt.h>
+#include <avr/pgmspace.h>
+#include "led.h"
+#include "sleep_led.h"
+
+#ifndef SLEEP_LED_TIMER
+#    define SLEEP_LED_TIMER 1
+#endif
+
+#if SLEEP_LED_TIMER == 1
+#    define TCCRxB TCCR1B
+#    define TIMERx_COMPA_vect TIMER1_COMPA_vect
+#    if defined(__AVR_ATmega32A__)  // This MCU has only one TIMSK register
+#        define TIMSKx TIMSK
+#    else
+#        define TIMSKx TIMSK1
+#    endif
+#    define OCIExA OCIE1A
+#    define OCRxx OCR1A
+#elif SLEEP_LED_TIMER == 3
+#    define TCCRxB TCCR3B
+#    define TIMERx_COMPA_vect TIMER3_COMPA_vect
+#    define TIMSKx TIMSK3
+#    define OCIExA OCIE3A
+#    define OCRxx OCR3A
+#else
+error("Invalid SLEEP_LED_TIMER config")
+#endif
+
+/* Software PWM
+ *  ______           ______           __
+ * |  ON  |___OFF___|  ON  |___OFF___|   ....
+ * |<-------------->|<-------------->|<- ....
+ *     PWM period       PWM period
+ *
+ * 256              interrupts/period[resolution]
+ * 64               periods/second[frequency]
+ * 256*64           interrupts/second
+ * F_CPU/(256*64)   clocks/interrupt
+ */
+#define SLEEP_LED_TIMER_TOP F_CPU / (256 * 64)
+
+/** \brief Sleep LED initialization
+ *
+ * FIXME: needs doc
+ */
+void sleep_led_init(void) {
+    /* Timer1 setup */
+    /* CTC mode */
+    TCCRxB |= _BV(WGM12);
+    /* Clock selelct: clk/1 */
+    TCCRxB |= _BV(CS10);
+    /* Set TOP value */
+    uint8_t sreg = SREG;
+    cli();
+    OCRxx = SLEEP_LED_TIMER_TOP;
+    SREG  = sreg;
+}
+
+/** \brief Sleep LED enable
+ *
+ * FIXME: needs doc
+ */
+void sleep_led_enable(void) {
+    /* Enable Compare Match Interrupt */
+    TIMSKx |= _BV(OCIExA);
+}
+
+/** \brief Sleep LED disable
+ *
+ * FIXME: needs doc
+ */
+void sleep_led_disable(void) {
+    /* Disable Compare Match Interrupt */
+    TIMSKx &= ~_BV(OCIExA);
+}
+
+/** \brief Sleep LED toggle
+ *
+ * FIXME: needs doc
+ */
+void sleep_led_toggle(void) {
+    /* Disable Compare Match Interrupt */
+    TIMSKx ^= _BV(OCIExA);
+}
+
+/** \brief Breathing Sleep LED brighness(PWM On period) table
+ *
+ * (64[steps] * 4[duration]) / 64[PWM periods/s] = 4 second breath cycle
+ *
+ * https://www.wolframalpha.com/input/?i=sin%28x%2F64*pi%29**8+*+255%2C+x%3D0+to+63
+ * (0..63).each {|x| p ((sin(x/64.0*PI)**8)*255).to_i }
+ */
+static const uint8_t breathing_table[64] PROGMEM = {0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 2, 4, 6, 10, 15, 23, 32, 44, 58, 74, 93, 113, 135, 157, 179, 199, 218, 233, 245, 252, 255, 252, 245, 233, 218, 199, 179, 157, 135, 113, 93, 74, 58, 44, 32, 23, 15, 10, 6, 4, 2, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0};
+
+ISR(TIMERx_COMPA_vect) {
+    /* Software PWM
+     * timer:1111 1111 1111 1111
+     *       \_____/\/ \_______/____  count(0-255)
+     *          \    \______________  duration of step(4)
+     *           \__________________  index of step table(0-63)
+     */
+    static union {
+        uint16_t row;
+        struct {
+            uint8_t count : 8;
+            uint8_t duration : 2;
+            uint8_t index : 6;
+        } pwm;
+    } timer = {.row = 0};
+
+    timer.row++;
+
+    // LED on
+    if (timer.pwm.count == 0) {
+        led_set(1 << USB_LED_CAPS_LOCK);
+    }
+    // LED off
+    if (timer.pwm.count == pgm_read_byte(&breathing_table[timer.pwm.index])) {
+        led_set(0);
+    }
+}
diff --git a/platforms/avr/suspend.c b/platforms/avr/suspend.c
new file mode 100644
index 000000000..b614746e6
--- /dev/null
+++ b/platforms/avr/suspend.c
@@ -0,0 +1,152 @@
+#include <stdbool.h>
+#include <avr/sleep.h>
+#include <avr/wdt.h>
+#include <avr/interrupt.h>
+#include "matrix.h"
+#include "action.h"
+#include "suspend.h"
+#include "timer.h"
+#include "led.h"
+#include "host.h"
+
+#ifdef PROTOCOL_LUFA
+#    include "lufa.h"
+#endif
+#ifdef PROTOCOL_VUSB
+#    include "vusb.h"
+#endif
+
+/** \brief Suspend idle
+ *
+ * FIXME: needs doc
+ */
+void suspend_idle(uint8_t time) {
+    cli();
+    set_sleep_mode(SLEEP_MODE_IDLE);
+    sleep_enable();
+    sei();
+    sleep_cpu();
+    sleep_disable();
+}
+
+// TODO: This needs some cleanup
+
+#if !defined(NO_SUSPEND_POWER_DOWN) && defined(WDT_vect)
+
+// clang-format off
+#define wdt_intr_enable(value) \
+__asm__ __volatile__ ( \
+    "in __tmp_reg__,__SREG__" "\n\t" \
+    "cli" "\n\t" \
+    "wdr" "\n\t" \
+    "sts %0,%1" "\n\t" \
+    "out __SREG__,__tmp_reg__" "\n\t" \
+    "sts %0,%2" "\n\t" \
+    : /* no outputs */ \
+    : "M" (_SFR_MEM_ADDR(_WD_CONTROL_REG)), \
+    "r" (_BV(_WD_CHANGE_BIT) | _BV(WDE)), \
+    "r" ((uint8_t) ((value & 0x08 ? _WD_PS3_MASK : 0x00) | _BV(WDIE) | (value & 0x07))) \
+    : "r0" \
+)
+// clang-format on
+
+/** \brief Power down MCU with watchdog timer
+ *
+ * wdto: watchdog timer timeout defined in <avr/wdt.h>
+ *          WDTO_15MS
+ *          WDTO_30MS
+ *          WDTO_60MS
+ *          WDTO_120MS
+ *          WDTO_250MS
+ *          WDTO_500MS
+ *          WDTO_1S
+ *          WDTO_2S
+ *          WDTO_4S
+ *          WDTO_8S
+ */
+static uint8_t wdt_timeout = 0;
+
+/** \brief Power down
+ *
+ * FIXME: needs doc
+ */
+static void power_down(uint8_t wdto) {
+    wdt_timeout = wdto;
+
+    // Watchdog Interrupt Mode
+    wdt_intr_enable(wdto);
+
+    // TODO: more power saving
+    // See PicoPower application note
+    // - I/O port input with pullup
+    // - prescale clock
+    // - BOD disable
+    // - Power Reduction Register PRR
+    set_sleep_mode(SLEEP_MODE_PWR_DOWN);
+    sleep_enable();
+    sei();
+    sleep_cpu();
+    sleep_disable();
+
+    // Disable watchdog after sleep
+    wdt_disable();
+}
+#endif
+
+/** \brief Suspend power down
+ *
+ * FIXME: needs doc
+ */
+void suspend_power_down(void) {
+#ifdef PROTOCOL_LUFA
+    if (USB_DeviceState == DEVICE_STATE_Configured) return;
+#endif
+#ifdef PROTOCOL_VUSB
+    if (!vusb_suspended) return;
+#endif
+
+    suspend_power_down_quantum();
+
+#ifndef NO_SUSPEND_POWER_DOWN
+    // Enter sleep state if possible (ie, the MCU has a watchdog timeout interrupt)
+#    if defined(WDT_vect)
+    power_down(WDTO_15MS);
+#    endif
+#endif
+}
+
+__attribute__((weak)) void matrix_power_up(void) {}
+__attribute__((weak)) void matrix_power_down(void) {}
+bool                       suspend_wakeup_condition(void) {
+    matrix_power_up();
+    matrix_scan();
+    matrix_power_down();
+    for (uint8_t r = 0; r < MATRIX_ROWS; r++) {
+        if (matrix_get_row(r)) return true;
+    }
+    return false;
+}
+
+/** \brief run immediately after wakeup
+ *
+ * FIXME: needs doc
+ */
+void suspend_wakeup_init(void) {
+    // clear keyboard state
+    clear_keyboard();
+
+    suspend_wakeup_init_quantum();
+}
+
+#if !defined(NO_SUSPEND_POWER_DOWN) && defined(WDT_vect)
+/* watchdog timeout */
+ISR(WDT_vect) {
+    // compensate timer for sleep
+    switch (wdt_timeout) {
+        case WDTO_15MS:
+            timer_count += 15 + 2;  // WDTO_15MS + 2(from observation)
+            break;
+        default:;
+    }
+}
+#endif
diff --git a/platforms/avr/timer.c b/platforms/avr/timer.c
new file mode 100644
index 000000000..c2e6c6e08
--- /dev/null
+++ b/platforms/avr/timer.c
@@ -0,0 +1,133 @@
+/*
+Copyright 2011 Jun Wako <wakojun@gmail.com>
+
+This program is free software: you can redistribute it and/or modify
+it under the terms of the GNU General Public License as published by
+the Free Software Foundation, either version 2 of the License, or
+(at your option) any later version.
+
+This program is distributed in the hope that it will be useful,
+but WITHOUT ANY WARRANTY; without even the implied warranty of
+MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+GNU General Public License for more details.
+
+You should have received a copy of the GNU General Public License
+along with this program.  If not, see <http://www.gnu.org/licenses/>.
+*/
+
+#include <avr/io.h>
+#include <avr/interrupt.h>
+#include <util/atomic.h>
+#include <stdint.h>
+#include "timer_avr.h"
+#include "timer.h"
+
+// counter resolution 1ms
+// NOTE: union { uint32_t timer32; struct { uint16_t dummy; uint16_t timer16; }}
+volatile uint32_t timer_count;
+
+/** \brief timer initialization
+ *
+ * FIXME: needs doc
+ */
+void timer_init(void) {
+#if TIMER_PRESCALER == 1
+    uint8_t prescaler = _BV(CS00);
+#elif TIMER_PRESCALER == 8
+    uint8_t prescaler = _BV(CS01);
+#elif TIMER_PRESCALER == 64
+    uint8_t prescaler = _BV(CS00) | _BV(CS01);
+#elif TIMER_PRESCALER == 256
+    uint8_t prescaler = _BV(CS02);
+#elif TIMER_PRESCALER == 1024
+    uint8_t prescaler = _BV(CS00) | _BV(CS02);
+#else
+#    error "Timer prescaler value is not valid"
+#endif
+
+#if defined(__AVR_ATmega32A__)
+    // Timer0 CTC mode
+    TCCR0 = _BV(WGM01) | prescaler;
+
+    OCR0  = TIMER_RAW_TOP;
+    TIMSK = _BV(OCIE0);
+#elif defined(__AVR_ATtiny85__)
+    // Timer0 CTC mode
+    TCCR0A = _BV(WGM01);
+    TCCR0B = prescaler;
+
+    OCR0A = TIMER_RAW_TOP;
+    TIMSK = _BV(OCIE0A);
+#else
+    // Timer0 CTC mode
+    TCCR0A = _BV(WGM01);
+    TCCR0B = prescaler;
+
+    OCR0A  = TIMER_RAW_TOP;
+    TIMSK0 = _BV(OCIE0A);
+#endif
+}
+
+/** \brief timer clear
+ *
+ * FIXME: needs doc
+ */
+inline void timer_clear(void) {
+    ATOMIC_BLOCK(ATOMIC_RESTORESTATE) { timer_count = 0; }
+}
+
+/** \brief timer read
+ *
+ * FIXME: needs doc
+ */
+inline uint16_t timer_read(void) {
+    uint32_t t;
+
+    ATOMIC_BLOCK(ATOMIC_RESTORESTATE) { t = timer_count; }
+
+    return (t & 0xFFFF);
+}
+
+/** \brief timer read32
+ *
+ * FIXME: needs doc
+ */
+inline uint32_t timer_read32(void) {
+    uint32_t t;
+
+    ATOMIC_BLOCK(ATOMIC_RESTORESTATE) { t = timer_count; }
+
+    return t;
+}
+
+/** \brief timer elapsed
+ *
+ * FIXME: needs doc
+ */
+inline uint16_t timer_elapsed(uint16_t last) {
+    uint32_t t;
+
+    ATOMIC_BLOCK(ATOMIC_RESTORESTATE) { t = timer_count; }
+
+    return TIMER_DIFF_16((t & 0xFFFF), last);
+}
+
+/** \brief timer elapsed32
+ *
+ * FIXME: needs doc
+ */
+inline uint32_t timer_elapsed32(uint32_t last) {
+    uint32_t t;
+
+    ATOMIC_BLOCK(ATOMIC_RESTORESTATE) { t = timer_count; }
+
+    return TIMER_DIFF_32(t, last);
+}
+
+// excecuted once per 1ms.(excess for just timer count?)
+#ifndef __AVR_ATmega32A__
+#    define TIMER_INTERRUPT_VECTOR TIMER0_COMPA_vect
+#else
+#    define TIMER_INTERRUPT_VECTOR TIMER0_COMP_vect
+#endif
+ISR(TIMER_INTERRUPT_VECTOR, ISR_NOBLOCK) { timer_count++; }
diff --git a/platforms/avr/timer_avr.h b/platforms/avr/timer_avr.h
new file mode 100644
index 000000000..c1b726bd0
--- /dev/null
+++ b/platforms/avr/timer_avr.h
@@ -0,0 +1,39 @@
+/*
+Copyright 2011 Jun Wako <wakojun@gmail.com>
+
+This program is free software: you can redistribute it and/or modify
+it under the terms of the GNU General Public License as published by
+the Free Software Foundation, either version 2 of the License, or
+(at your option) any later version.
+
+This program is distributed in the hope that it will be useful,
+but WITHOUT ANY WARRANTY; without even the implied warranty of
+MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+GNU General Public License for more details.
+
+You should have received a copy of the GNU General Public License
+along with this program.  If not, see <http://www.gnu.org/licenses/>.
+*/
+
+#pragma once
+
+#include <stdint.h>
+
+#ifndef TIMER_PRESCALER
+#    if F_CPU > 16000000
+#        define TIMER_PRESCALER 256
+#    elif F_CPU > 2000000
+#        define TIMER_PRESCALER 64
+#    elif F_CPU > 250000
+#        define TIMER_PRESCALER 8
+#    else
+#        define TIMER_PRESCALER 1
+#    endif
+#endif
+#define TIMER_RAW_FREQ (F_CPU / TIMER_PRESCALER)
+#define TIMER_RAW TCNT0
+#define TIMER_RAW_TOP (TIMER_RAW_FREQ / 1000)
+
+#if (TIMER_RAW_TOP > 255)
+#    error "Timer0 can't count 1ms at this clock freq. Use larger prescaler."
+#endif
diff --git a/platforms/avr/xprintf.S b/platforms/avr/xprintf.S
new file mode 100644
index 000000000..c5a414c35
--- /dev/null
+++ b/platforms/avr/xprintf.S
@@ -0,0 +1,498 @@
+;---------------------------------------------------------------------------;
+; Extended itoa, puts, printf and atoi                     (C)ChaN, 2011
+;---------------------------------------------------------------------------;
+
+                                // Base size is 152 bytes
+#define CR_CRLF         0       // Convert \n to \r\n (+10 bytes)
+#define USE_XPRINTF     1       // Enable xprintf function (+194 bytes)
+#define USE_XSPRINTF    0       // Add xsprintf function (+78 bytes)
+#define USE_XFPRINTF    0       // Add xfprintf function (+54 bytes)
+#define USE_XATOI       0       // Enable xatoi function (+182 bytes)
+
+
+#if FLASHEND > 0x1FFFF
+#error xitoa module does not support 256K devices
+#endif
+
+.nolist
+#include <avr/io.h>     // Include device specific definitions.
+.list
+
+#ifdef SPM_PAGESIZE     // Recent devices have "lpm Rd,Z+" and "movw".
+.macro  _LPMI   reg
+        lpm     \reg, Z+
+.endm
+.macro  _MOVW   dh,dl, sh,sl
+        movw    \dl, \sl
+.endm
+#else                   // Earlier devices do not have "lpm Rd,Z+" nor "movw".
+.macro  _LPMI   reg
+        lpm
+        mov     \reg, r0
+        adiw    ZL, 1
+.endm
+.macro  _MOVW   dh,dl, sh,sl
+        mov     \dl, \sl
+        mov     \dh, \sh
+.endm
+#endif
+
+
+
+;---------------------------------------------------------------------------
+; Stub function to forward to user output function
+;
+;Prototype: void xputc (char chr        // a character to be output
+;                       );
+;Size: 12/12 words
+
+.section .bss
+.global xfunc_out       ; xfunc_out must be initialized before using this module.
+xfunc_out:      .ds.w   1
+.section .text
+
+
+.func xputc
+.global xputc
+xputc:
+#if CR_CRLF
+        cpi     r24, 10         ;LF --> CRLF
+        brne    1f              ;
+        ldi     r24, 13         ;
+        rcall   1f              ;
+        ldi     r24, 10         ;/
+1:
+#endif
+        push    ZH
+        push    ZL
+        lds     ZL, xfunc_out+0 ;Pointer to the registered output function.
+        lds     ZH, xfunc_out+1 ;/
+        sbiw    ZL, 0           ;Skip if null
+        breq    2f              ;/
+        icall
+2:      pop     ZL
+        pop     ZH
+        ret
+.endfunc
+
+
+
+;---------------------------------------------------------------------------
+; Direct ROM string output
+;
+;Prototype: void xputs (const char *str_p // rom string to be output
+;                       );
+
+.func xputs
+.global xputs
+xputs:
+        _MOVW   ZH,ZL, r25,r24  ; Z = pointer to rom string
+1:      _LPMI   r24
+        cpi     r24, 0
+        breq    2f
+        rcall   xputc
+        rjmp    1b
+2:      ret
+.endfunc
+
+
+;---------------------------------------------------------------------------
+; Extended direct numeral string output (32bit version)
+;
+;Prototype: void xitoa (long value,     // value to be output
+;                       char radix,     // radix
+;                       char width);    // minimum width
+;
+
+.func xitoa
+.global xitoa
+xitoa:
+                                ;r25:r22 = value, r20 = base, r18 = digits
+        clr     r31             ;r31 = stack level
+        ldi     r30, ' '        ;r30 = sign
+        ldi     r19, ' '        ;r19 = filler
+        sbrs    r20, 7          ;When base indicates signd format and the value
+        rjmp    0f              ;is minus, add a '-'.
+        neg     r20             ;
+        sbrs    r25, 7          ;
+        rjmp    0f              ;
+        ldi     r30, '-'        ;
+        com     r22             ;
+        com     r23             ;
+        com     r24             ;
+        com     r25             ;
+        adc     r22, r1         ;
+        adc     r23, r1         ;
+        adc     r24, r1         ;
+        adc     r25, r1         ;/
+0:      sbrs    r18, 7          ;When digits indicates zero filled,
+        rjmp    1f              ;filler is '0'.
+        neg     r18             ;
+        ldi     r19, '0'        ;/
+                                ;----- string conversion loop
+1:      ldi     r21, 32         ;r26 = r25:r22 % r20
+        clr     r26             ;r25:r22 /= r20
+2:      lsl     r22             ;
+        rol     r23             ;
+        rol     r24             ;
+        rol     r25             ;
+        rol     r26             ;
+        cp      r26, r20        ;
+        brcs    3f              ;
+        sub     r26, r20        ;
+        inc     r22             ;
+3:      dec     r21             ;
+        brne    2b              ;/
+        cpi     r26, 10         ;r26 is a numeral digit '0'-'F'
+        brcs    4f              ;
+        subi    r26, -7         ;
+4:      subi    r26, -'0'       ;/
+        push    r26             ;Stack it
+        inc     r31             ;/
+        cp      r22, r1         ;Repeat until r25:r22 gets zero
+        cpc     r23, r1         ;
+        cpc     r24, r1         ;
+        cpc     r25, r1         ;
+        brne    1b              ;/
+
+        cpi     r30, '-'        ;Minus sign if needed
+        brne    5f              ;
+        push    r30             ;
+        inc     r31             ;/
+5:      cp      r31, r18        ;Filler
+        brcc    6f              ;
+        push    r19             ;
+        inc     r31             ;
+        rjmp    5b              ;/
+
+6:      pop     r24             ;Flush stacked digits and exit
+        rcall   xputc           ;
+        dec     r31             ;
+        brne    6b              ;/
+
+        ret
+.endfunc
+
+
+
+;---------------------------------------------------------------------------;
+; Formatted string output (16/32bit version)
+;
+;Prototype:
+; void __xprintf (const char *format_p, ...);
+; void __xsprintf(char*, const char *format_p, ...);
+; void __xfprintf(void(*func)(char), const char *format_p, ...);
+;
+
+#if USE_XPRINTF
+
+.func xvprintf
+xvprintf:
+        ld      ZL, Y+          ;Z = pointer to format string
+        ld      ZH, Y+          ;/
+
+0:      _LPMI   r24             ;Get a format char
+        cpi     r24, 0          ;End of format string?
+        breq    90f             ;/
+        cpi     r24, '%'        ;Is format?
+        breq    20f             ;/
+1:      rcall   xputc           ;Put a normal character
+        rjmp    0b              ;/
+90:     ret
+
+20:     ldi     r18, 0          ;r18: digits
+        clt                     ;T: filler
+        _LPMI   r21             ;Get flags
+        cpi     r21, '%'        ;Is a %?
+        breq    1b              ;/
+        cpi     r21, '0'        ;Zero filled?
+        brne    23f             ;
+        set                     ;/
+22:     _LPMI   r21             ;Get width
+23:     cpi     r21, '9'+1      ;
+        brcc    24f             ;
+        subi    r21, '0'        ;
+        brcs    90b             ;
+        lsl     r18             ;
+        mov     r0, r18         ;
+        lsl     r18             ;
+        lsl     r18             ;
+        add     r18, r0         ;
+        add     r18, r21        ;
+        rjmp    22b             ;/
+
+24:     brtc    25f             ;get value (low word)
+        neg     r18             ;
+25:     ld      r24, Y+         ;
+        ld      r25, Y+         ;/
+        cpi     r21, 'c'        ;Is type character?
+        breq    1b              ;/
+        cpi     r21, 's'        ;Is type RAM string?
+        breq    50f             ;/
+        cpi     r21, 'S'        ;Is type ROM string?
+        breq    60f             ;/
+        _MOVW   r23,r22,r25,r24 ;r25:r22 = value
+        clr     r24             ;
+        clr     r25             ;
+        clt                     ;/
+        cpi     r21, 'l'        ;Is long int?
+        brne    26f             ;
+        ld      r24, Y+         ;get value (high word)
+        ld      r25, Y+         ;
+        set                     ;
+        _LPMI   r21             ;/
+26:     cpi     r21, 'd'        ;Is type signed decimal?
+        brne    27f             ;/
+        ldi     r20, -10        ;
+        brts    40f             ;
+        sbrs    r23, 7          ;
+        rjmp    40f             ;
+        ldi     r24, -1         ;
+        ldi     r25, -1         ;
+        rjmp    40f             ;/
+27:     cpi     r21, 'u'        ;Is type unsigned decimal?
+        ldi     r20, 10         ;
+        breq    40f             ;/
+        cpi     r21, 'X'        ;Is type hexdecimal?
+        ldi     r20, 16         ;
+        breq    40f             ;/
+        cpi     r21, 'b'        ;Is type binary?
+        ldi     r20, 2          ;
+        breq    40f             ;/
+        ret                     ;abort
+40:     push    ZH              ;Output the value
+        push    ZL              ;
+        rcall   xitoa           ;
+42:     pop     ZL              ;
+        pop     ZH              ;
+        rjmp    0b              ;/
+
+50:     push    ZH              ;Put a string on the RAM
+        push    ZL
+        _MOVW   ZH,ZL, r25,r24
+51:     ld      r24, Z+
+        cpi     r24, 0
+        breq    42b
+        rcall   xputc
+        rjmp    51b
+
+60:     push    ZH              ;Put a string on the ROM
+        push    ZL
+        rcall   xputs
+        rjmp    42b
+.endfunc
+
+
+.func __xprintf
+.global __xprintf
+__xprintf:
+        push    YH
+        push    YL
+        in      YL, _SFR_IO_ADDR(SPL)
+#ifdef SPH
+        in      YH, _SFR_IO_ADDR(SPH)
+#else
+        clr     YH
+#endif
+        adiw    YL, 5           ;Y = pointer to arguments
+        rcall   xvprintf
+        pop     YL
+        pop     YH
+        ret
+.endfunc
+
+
+#if USE_XSPRINTF
+
+.func __xsprintf
+putram:
+        _MOVW   ZH,ZL, r15,r14
+        st      Z+, r24
+        _MOVW   r15,r14, ZH,ZL
+        ret
+.global __xsprintf
+__xsprintf:
+        push    YH
+        push    YL
+        in      YL, _SFR_IO_ADDR(SPL)
+#ifdef SPH
+        in      YH, _SFR_IO_ADDR(SPH)
+#else
+        clr     YH
+#endif
+        adiw    YL, 5           ;Y = pointer to arguments
+        lds     ZL, xfunc_out+0 ;Save registered output function
+        lds     ZH, xfunc_out+1 ;
+        push    ZL              ;
+        push    ZH              ;/
+        ldi     ZL, lo8(pm(putram));Set local output function
+        ldi     ZH, hi8(pm(putram));
+        sts     xfunc_out+0, ZL ;
+        sts     xfunc_out+1, ZH ;/
+        push    r15             ;Initialize pointer to string buffer
+        push    r14             ;
+        ld      r14, Y+         ;
+        ld      r15, Y+         ;/
+        rcall   xvprintf
+        _MOVW   ZH,ZL, r15,r14  ;Terminate string
+        st      Z, r1           ;
+        pop     r14             ;
+        pop     r15             ;/
+        pop     ZH              ;Restore registered output function
+        pop     ZL              ;
+        sts     xfunc_out+0, ZL ;
+        sts     xfunc_out+1, ZH ;/
+        pop     YL
+        pop     YH
+        ret
+.endfunc
+#endif
+
+
+#if USE_XFPRINTF
+.func __xfprintf
+.global __xfprintf
+__xfprintf:
+        push    YH
+        push    YL
+        in      YL, _SFR_IO_ADDR(SPL)
+#ifdef SPH
+        in      YH, _SFR_IO_ADDR(SPH)
+#else
+        clr     YH
+#endif
+        adiw    YL, 5           ;Y = pointer to arguments
+        lds     ZL, xfunc_out+0 ;Save registered output function
+        lds     ZH, xfunc_out+1 ;
+        push    ZL              ;
+        push    ZH              ;/
+        ld      ZL, Y+          ;Set output function
+        ld      ZH, Y+          ;
+        sts     xfunc_out+0, ZL ;
+        sts     xfunc_out+1, ZH ;/
+        rcall   xvprintf
+        pop     ZH              ;Restore registered output function
+        pop     ZL              ;
+        sts     xfunc_out+0, ZL ;
+        sts     xfunc_out+1, ZH ;/
+        pop     YL
+        pop     YH
+        ret
+.endfunc
+#endif
+
+#endif
+
+
+
+;---------------------------------------------------------------------------
+; Extended numeral string input
+;
+;Prototype:
+; char xatoi (           /* 1: Successful, 0: Failed */
+;      const char **str, /* pointer to pointer to source string */
+;      long *res         /* result */
+; );
+;
+
+
+#if USE_XATOI
+.func xatoi
+.global xatoi
+xatoi:
+        _MOVW   r1, r0, r23, r22
+        _MOVW   XH, XL, r25, r24
+        ld      ZL, X+
+        ld      ZH, X+
+        clr     r18             ;r21:r18 = 0;
+        clr     r19             ;
+        clr     r20             ;
+        clr     r21             ;/
+        clt                     ;T = 0;
+
+        ldi     r25, 10         ;r25 = 10;
+        rjmp    41f             ;/
+40:     adiw    ZL, 1           ;Z++;
+41:     ld      r22, Z          ;r22 = *Z;
+        cpi     r22, ' '        ;if(r22 == ' ') continue
+        breq    40b             ;/
+        brcs    70f             ;if(r22 < ' ') error;
+        cpi     r22, '-'        ;if(r22 == '-') {
+        brne    42f             ; T = 1;
+        set                     ; continue;
+        rjmp    40b             ;}
+42:     cpi     r22, '9'+1      ;if(r22 > '9') error;
+        brcc    70f             ;/
+        cpi     r22, '0'        ;if(r22 < '0') error;
+        brcs    70f             ;/
+        brne    51f             ;if(r22 > '0') cv_start;
+        ldi     r25, 8          ;r25 = 8;
+        adiw    ZL, 1           ;r22 = *(++Z);
+        ld      r22, Z          ;/
+        cpi     r22, ' '+1      ;if(r22 <= ' ') exit;
+        brcs    80f             ;/
+        cpi     r22, 'b'        ;if(r22 == 'b') {
+        brne    43f             ; r25 = 2;
+        ldi     r25, 2          ; cv_start;
+        rjmp    50f             ;}
+43:     cpi     r22, 'x'        ;if(r22 != 'x') error;
+        brne    51f             ;/
+        ldi     r25, 16         ;r25 = 16;
+
+50:     adiw    ZL, 1           ;Z++;
+        ld      r22, Z          ;r22 = *Z;
+51:     cpi     r22, ' '+1      ;if(r22 <= ' ') break;
+        brcs    80f             ;/
+        cpi     r22, 'a'        ;if(r22 >= 'a') r22 =- 0x20;
+        brcs    52f             ;
+        subi    r22, 0x20       ;/
+52:     subi    r22, '0'        ;if((r22 -= '0') < 0) error;
+        brcs    70f             ;/
+        cpi     r22, 10         ;if(r22 >= 10) {
+        brcs    53f             ; r22 -= 7;
+        subi    r22, 7          ; if(r22 < 10)
+        cpi     r22, 10         ;
+        brcs    70f             ;}
+53:     cp      r22, r25        ;if(r22 >= r25) error;
+        brcc    70f             ;/
+60:     ldi     r24, 33         ;r21:r18 *= r25;
+        sub     r23, r23        ;
+61:     brcc    62f             ;
+        add     r23, r25        ;
+62:     lsr     r23             ;
+        ror     r21             ;
+        ror     r20             ;
+        ror     r19             ;
+        ror     r18             ;
+        dec     r24             ;
+        brne    61b             ;/
+        add     r18, r22        ;r21:r18 += r22;
+        adc     r19, r24        ;
+        adc     r20, r24        ;
+        adc     r21, r24        ;/
+        rjmp    50b             ;repeat
+
+70:     ldi     r24, 0
+        rjmp    81f
+80:     ldi     r24, 1
+81:     brtc    82f
+        clr     r22
+        com     r18
+        com     r19
+        com     r20
+        com     r21
+        adc     r18, r22
+        adc     r19, r22
+        adc     r20, r22
+        adc     r21, r22
+82:     st      -X, ZH
+        st      -X, ZL
+        _MOVW   XH, XL, r1, r0
+        st      X+, r18
+        st      X+, r19
+        st      X+, r20
+        st      X+, r21
+        clr     r1
+        ret
+.endfunc
+#endif
diff --git a/platforms/avr/xprintf.h b/platforms/avr/xprintf.h
new file mode 100644
index 000000000..80834f171
--- /dev/null
+++ b/platforms/avr/xprintf.h
@@ -0,0 +1,103 @@
+/*---------------------------------------------------------------------------
+   Extended itoa, puts and printf                    (C)ChaN, 2011
+-----------------------------------------------------------------------------*/
+
+#pragma once
+
+#include <inttypes.h>
+#include <avr/pgmspace.h>
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+extern void (*xfunc_out)(uint8_t);
+#define xdev_out(func) xfunc_out = (void (*)(uint8_t))(func)
+
+/* This is a pointer to user defined output function. It must be initialized
+   before using this modle.
+*/
+
+void xputc(char chr);
+
+/* This is a stub function to forward outputs to user defined output function.
+   All outputs from this module are output via this function.
+*/
+
+/*-----------------------------------------------------------------------------*/
+void xputs(const char *string_p);
+
+/*  The string placed in the ROM is forwarded to xputc() directly.
+ */
+
+/*-----------------------------------------------------------------------------*/
+void xitoa(long value, char radix, char width);
+
+/* Extended itoa().
+
+      value  radix  width   output
+        100     10      6   "   100"
+        100     10     -6   "000100"
+        100     10      0   "100"
+ 4294967295     10      0   "4294967295"
+ 4294967295    -10      0   "-1"
+     655360     16     -8   "000A0000"
+       1024     16      0   "400"
+       0x55      2     -8   "01010101"
+*/
+
+/*-----------------------------------------------------------------------------*/
+#define xprintf(format, ...) __xprintf(PSTR(format), ##__VA_ARGS__)
+#define xsprintf(str, format, ...) __xsprintf(str, PSTR(format), ##__VA_ARGS__)
+#define xfprintf(func, format, ...) __xfprintf(func, PSTR(format), ##__VA_ARGS__)
+
+void __xprintf(const char *format_p, ...); /* Send formatted string to the registered device */
+// void __xsprintf(char*, const char *format_p, ...);   /* Put formatted string to the memory */
+// void __xfprintf(void(*func)(uint8_t), const char *format_p, ...); /* Send formatted string to the specified device */
+
+/* Format string is placed in the ROM. The format flags is similar to printf().
+
+   %[flag][width][size]type
+
+   flag
+     A '0' means filled with '0' when output is shorter than width.
+     ' ' is used in default. This is effective only numeral type.
+   width
+     Minimum width in decimal number. This is effective only numeral type.
+     Default width is zero.
+   size
+     A 'l' means the argument is long(32bit). Default is short(16bit).
+     This is effective only numeral type.
+   type
+     'c' : Character, argument is the value
+     's' : String placed on the RAM, argument is the pointer
+     'S' : String placed on the ROM, argument is the pointer
+     'd' : Signed decimal, argument is the value
+     'u' : Unsigned decimal, argument is the value
+     'X' : Hexdecimal, argument is the value
+     'b' : Binary, argument is the value
+     '%' : '%'
+
+*/
+
+/*-----------------------------------------------------------------------------*/
+char xatoi(char **str, long *ret);
+
+/* Get value of the numeral string.
+
+  str
+    Pointer to pointer to source string
+
+    "0b11001010" binary
+    "0377" octal
+    "0xff800" hexdecimal
+    "1250000" decimal
+    "-25000" decimal
+
+  ret
+    Pointer to return value
+*/
+
+#ifdef __cplusplus
+}
+#endif