i2c working

20 files changed, 1827 insertions, 21 deletions

diff --git a/keyboards/lets-split/lets-split.h b/keyboards/lets-split/lets-split.h
deleted file mode 100644
index c82b95a37..000000000
--- a/keyboards/lets-split/lets-split.h
+++ /dev/null
@@ -1,4 +0,0 @@
-#include "quantum.h"
-#include <avr/wdt.h>
-
-void promicro_bootloader_jmp(bool program);
\ No newline at end of file
diff --git a/keyboards/lets-split/Makefile b/keyboards/lets_split/Makefile
index 247f978f0..d8e283896 100644
--- a/keyboards/lets-split/Makefile
+++ b/keyboards/lets_split/Makefile
@@ -1,4 +1,6 @@
-
+SRC += matrix.c \
+           i2c.c \
+           split_util.c
 
 # MCU name
 #MCU = at90usb1287
@@ -68,6 +70,8 @@ RGBLIGHT_ENABLE ?= no        # Enable WS2812 RGB underlight.  Do not enable this
 # Do not enable SLEEP_LED_ENABLE. it uses the same timer as BACKLIGHT_ENABLE
 SLEEP_LED_ENABLE ?= no    # Breathing sleep LED during USB suspend
 
+CUSTOM_MATRIX = yes
+
 ifndef QUANTUM_DIR
         include ../../Makefile
 endif
\ No newline at end of file
diff --git a/keyboards/lets-split/config.h b/keyboards/lets_split/config.h
index 5b464147d..e68787e0b 100644
--- a/keyboards/lets-split/config.h
+++ b/keyboards/lets_split/config.h
@@ -29,12 +29,18 @@ along with this program.  If not, see <http://www.gnu.org/licenses/>.
 #define DESCRIPTION     A split keyboard for the cheap makers
 
 /* key matrix size */
-#define MATRIX_ROWS 4
+#define MATRIX_ROWS 8
 #define MATRIX_COLS 6
 
-#define MATRIX_ROW_PINS { B5, B4, E6, D7, }
+// wiring of each half
+#define MATRIX_ROW_PINS { B5, B4, E6, D7 }
 #define MATRIX_COL_PINS { F4, F5, F6, F7, B1, B3 }
 
+#define USE_I2C
+
+// #define I2C_MASTER_LEFT
+#define I2C_MASTER_RIGHT
+
 /* COL2ROW or ROW2COL */
 #define DIODE_DIRECTION COL2ROW
 
diff --git a/keyboards/lets_split/i2c.c b/keyboards/lets_split/i2c.c
new file mode 100644
index 000000000..c72789403
--- /dev/null
+++ b/keyboards/lets_split/i2c.c
@@ -0,0 +1,159 @@
+#include <util/twi.h>
+#include <avr/io.h>
+#include <stdlib.h>
+#include <avr/interrupt.h>
+#include <util/twi.h>
+#include <stdbool.h>
+#include "i2c.h"
+
+// Limits the amount of we wait for any one i2c transaction.
+// Since were running SCL line 100kHz (=> 10μs/bit), and each transactions is
+// 9 bits, a single transaction will take around 90μs to complete.
+//
+// (F_CPU/SCL_CLOCK)  =>  # of μC cycles to transfer a bit
+// poll loop takes at least 8 clock cycles to execute
+#define I2C_LOOP_TIMEOUT (9+1)*(F_CPU/SCL_CLOCK)/8
+
+#define BUFFER_POS_INC() (slave_buffer_pos = (slave_buffer_pos+1)%SLAVE_BUFFER_SIZE)
+
+volatile uint8_t i2c_slave_buffer[SLAVE_BUFFER_SIZE];
+
+static volatile uint8_t slave_buffer_pos;
+static volatile bool slave_has_register_set = false;
+
+// Wait for an i2c operation to finish
+inline static
+void i2c_delay(void) {
+  uint16_t lim = 0;
+  while(!(TWCR & (1<<TWINT)) && lim < I2C_LOOP_TIMEOUT)
+    lim++;
+
+  // easier way, but will wait slightly longer
+  // _delay_us(100);
+}
+
+// Setup twi to run at 100kHz
+void i2c_master_init(void) {
+  // no prescaler
+  TWSR = 0;
+  // Set TWI clock frequency to SCL_CLOCK. Need TWBR>10.
+  // Check datasheets for more info.
+  TWBR = ((F_CPU/SCL_CLOCK)-16)/2;
+}
+
+// Start a transaction with the given i2c slave address. The direction of the
+// transfer is set with I2C_READ and I2C_WRITE.
+// returns: 0 => success
+//          1 => error
+uint8_t i2c_master_start(uint8_t address) {
+  TWCR = (1<<TWINT) | (1<<TWEN) | (1<<TWSTA);
+
+  i2c_delay();
+
+  // check that we started successfully
+  if ( (TW_STATUS != TW_START) && (TW_STATUS != TW_REP_START))
+    return 1;
+
+  TWDR = address;
+  TWCR = (1<<TWINT) | (1<<TWEN);
+
+  i2c_delay();
+
+  if ( (TW_STATUS != TW_MT_SLA_ACK) && (TW_STATUS != TW_MR_SLA_ACK) )
+    return 1; // slave did not acknowledge
+  else
+    return 0; // success
+}
+
+
+// Finish the i2c transaction.
+void i2c_master_stop(void) {
+  TWCR = (1<<TWINT) | (1<<TWEN) | (1<<TWSTO);
+
+  uint16_t lim = 0;
+  while(!(TWCR & (1<<TWSTO)) && lim < I2C_LOOP_TIMEOUT)
+    lim++;
+}
+
+// Write one byte to the i2c slave.
+// returns 0 => slave ACK
+//         1 => slave NACK
+uint8_t i2c_master_write(uint8_t data) {
+  TWDR = data;
+  TWCR = (1<<TWINT) | (1<<TWEN);
+
+  i2c_delay();
+
+  // check if the slave acknowledged us
+  return (TW_STATUS == TW_MT_DATA_ACK) ? 0 : 1;
+}
+
+// Read one byte from the i2c slave. If ack=1 the slave is acknowledged,
+// if ack=0 the acknowledge bit is not set.
+// returns: byte read from i2c device
+uint8_t i2c_master_read(int ack) {
+  TWCR = (1<<TWINT) | (1<<TWEN) | (ack<<TWEA);
+
+  i2c_delay();
+  return TWDR;
+}
+
+void i2c_reset_state(void) {
+  TWCR = 0;
+}
+
+void i2c_slave_init(uint8_t address) {
+  TWAR = address << 0; // slave i2c address
+  // TWEN  - twi enable
+  // TWEA  - enable address acknowledgement
+  // TWINT - twi interrupt flag
+  // TWIE  - enable the twi interrupt
+  TWCR = (1<<TWIE) | (1<<TWEA) | (1<<TWINT) | (1<<TWEN);
+}
+
+ISR(TWI_vect);
+
+ISR(TWI_vect) {
+  uint8_t ack = 1;
+  switch(TW_STATUS) {
+    case TW_SR_SLA_ACK:
+      // this device has been addressed as a slave receiver
+      slave_has_register_set = false;
+      break;
+
+    case TW_SR_DATA_ACK:
+      // this device has received data as a slave receiver
+      // The first byte that we receive in this transaction sets the location
+      // of the read/write location of the slaves memory that it exposes over
+      // i2c.  After that, bytes will be written at slave_buffer_pos, incrementing
+      // slave_buffer_pos after each write.
+      if(!slave_has_register_set) {
+        slave_buffer_pos = TWDR;
+        // don't acknowledge the master if this memory loctaion is out of bounds
+        if ( slave_buffer_pos >= SLAVE_BUFFER_SIZE ) {
+          ack = 0;
+          slave_buffer_pos = 0;
+        }
+        slave_has_register_set = true;
+      } else {
+        i2c_slave_buffer[slave_buffer_pos] = TWDR;
+        BUFFER_POS_INC();
+      }
+      break;
+
+    case TW_ST_SLA_ACK:
+    case TW_ST_DATA_ACK:
+      // master has addressed this device as a slave transmitter and is
+      // requesting data.
+      TWDR = i2c_slave_buffer[slave_buffer_pos];
+      BUFFER_POS_INC();
+      break;
+
+    case TW_BUS_ERROR: // something went wrong, reset twi state
+      TWCR = 0;
+    default:
+      break;
+  }
+  // Reset everything, so we are ready for the next TWI interrupt
+  TWCR |= (1<<TWIE) | (1<<TWINT) | (ack<<TWEA) | (1<<TWEN);
+}
diff --git a/keyboards/lets_split/i2c.h b/keyboards/lets_split/i2c.h
new file mode 100644
index 000000000..08ce4b009
--- /dev/null
+++ b/keyboards/lets_split/i2c.h
@@ -0,0 +1,31 @@
+#ifndef I2C_H
+#define I2C_H
+
+#include <stdint.h>
+
+#ifndef F_CPU
+#define F_CPU 16000000UL
+#endif
+
+#define I2C_READ 1
+#define I2C_WRITE 0
+
+#define I2C_ACK 1
+#define I2C_NACK 0
+
+#define SLAVE_BUFFER_SIZE 0x10
+
+// i2c SCL clock frequency
+#define SCL_CLOCK  100000L
+
+extern volatile uint8_t i2c_slave_buffer[SLAVE_BUFFER_SIZE];
+
+void i2c_master_init(void);
+uint8_t i2c_master_start(uint8_t address);
+void i2c_master_stop(void);
+uint8_t i2c_master_write(uint8_t data);
+uint8_t i2c_master_read(int);
+void i2c_reset_state(void);
+void i2c_slave_init(uint8_t address);
+
+#endif
diff --git a/keyboards/lets-split/keymaps/default/keymap.c b/keyboards/lets_split/keymaps/default/keymap.c
index 00602394f..01e3593c2 100644
--- a/keyboards/lets-split/keymaps/default/keymap.c
+++ b/keyboards/lets_split/keymaps/default/keymap.c
@@ -1,4 +1,4 @@
-#include "lets-split.h"
+#include "lets_split.h"
 #include "action_layer.h"
 
 #define BASE 0
@@ -14,12 +14,12 @@ enum preonic_keycodes {
 
 const uint16_t PROGMEM keymaps[][MATRIX_ROWS][MATRIX_COLS] = {
 
-[BASE] = {
-  {KC_TAB,  KC_Q,    KC_W,    KC_E,    KC_R,    KC_T     },
-  {KC_ESC,  KC_A,    KC_S,    KC_D,    KC_F,    KC_G     },
-  {KC_LSFT, KC_Z,    KC_X,    KC_C,    KC_V,    KC_B     },
-  {KC_IDK,  KC_LCTL, KC_LALT, KC_LGUI, KC_SPC,  PM_RESET }
-}
+[BASE] = KEYMAP(
+  KC_TAB,  KC_Q,    KC_W,    KC_E,    KC_R,    KC_T,        KC_Y,    KC_U,    KC_I,    KC_O,    KC_P,    KC_BSPC, \
+  KC_ESC,  KC_A,    KC_S,    KC_D,    KC_F,    KC_G,        KC_H,    KC_J,    KC_K,    KC_L,    KC_SCLN, KC_QUOT, \
+  KC_LSFT, KC_Z,    KC_X,    KC_C,    KC_V,    KC_B,        KC_N,    KC_M,    KC_COMM, KC_DOT,  KC_SLSH, KC_ENT, \
+  KC_IDK,  KC_LCTL, KC_LALT, KC_LGUI, PM_RESET,KC_SPC,      KC_SPC,  PM_RESET,KC_LEFT, KC_DOWN, KC_UP,   KC_RGHT \
+)
 
 };
 
diff --git a/keyboards/lets-split/lets-split.c b/keyboards/lets_split/lets_split.c
index ee9872303..1859dc20a 100644
--- a/keyboards/lets-split/lets-split.c
+++ b/keyboards/lets_split/lets_split.c
@@ -1,4 +1,4 @@
-#include "lets-split.h"
+#include "lets_split.h"
 
 #ifdef AUDIO_ENABLE
     float tone_startup[][2] = SONG(STARTUP_SOUND);
@@ -12,13 +12,13 @@ void matrix_init_kb(void) {
         PLAY_NOTE_ARRAY(tone_startup, false, 0);
     #endif
 
-    // green led on
-    DDRD |= (1<<5);
-    PORTD &= ~(1<<5);
+    // // green led on
+    // DDRD |= (1<<5);
+    // PORTD &= ~(1<<5);
 
-    // orange led on
-    DDRB |= (1<<0);
-    PORTB &= ~(1<<0);
+    // // orange led on
+    // DDRB |= (1<<0);
+    // PORTB &= ~(1<<0);
 
         matrix_init_user();
 };
diff --git a/keyboards/lets_split/lets_split.h b/keyboards/lets_split/lets_split.h
new file mode 100644
index 000000000..e59aed592
--- /dev/null
+++ b/keyboards/lets_split/lets_split.h
@@ -0,0 +1,21 @@
+#include "quantum.h"
+#include <avr/wdt.h>
+
+void promicro_bootloader_jmp(bool program);
+
+#define KEYMAP( \
+        k00, k01, k02, k03, k04, k05, k40, k41, k42, k43, k44, k45, \
+        k10, k11, k12, k13, k14, k15, k50, k51, k52, k53, k54, k55, \
+        k20, k21, k22, k23, k24, k25, k60, k61, k62, k63, k64, k65, \
+        k30, k31, k32, k33, k34, k35, k70, k71, k72, k73, k74, k75 \
+        ) \
+        { \
+                { k00, k01, k02, k03, k04, k05 }, \
+                { k10, k11, k12, k13, k14, k15 }, \
+                { k20, k21, k22, k23, k24, k25 }, \
+                { k30, k31, k32, k33, k34, k35 }, \
+                { k40, k41, k42, k43, k44, k45 }, \
+                { k50, k51, k52, k53, k54, k55 }, \
+                { k60, k61, k62, k63, k64, k65 }, \
+                { k70, k71, k72, k73, k74, k75 } \
+        }
\ No newline at end of file
diff --git a/keyboards/lets_split/matrix.c b/keyboards/lets_split/matrix.c
new file mode 100644
index 000000000..16c2ba0ba
--- /dev/null
+++ b/keyboards/lets_split/matrix.c
@@ -0,0 +1,310 @@
+/*
+Copyright 2012 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/>.
+*/
+
+/*
+ * scan matrix
+ */
+#include <stdint.h>
+#include <stdbool.h>
+#include <avr/io.h>
+#include <avr/wdt.h>
+#include <avr/interrupt.h>
+#include <util/delay.h>
+#include "print.h"
+#include "debug.h"
+#include "util.h"
+#include "matrix.h"
+#include "i2c.h"
+#include "split_util.h"
+#include "pro_micro.h"
+#include "config.h"
+
+#ifndef DEBOUNCE
+#   define DEBOUNCE     5
+#endif
+
+#define ERROR_DISCONNECT_COUNT 5
+
+static uint8_t debouncing = DEBOUNCE;
+static const int ROWS_PER_HAND = MATRIX_ROWS/2;
+static uint8_t error_count = 0;
+
+static const uint8_t row_pins[MATRIX_ROWS] = MATRIX_ROW_PINS;
+static const uint8_t col_pins[MATRIX_COLS] = MATRIX_COL_PINS;
+
+/* matrix state(1:on, 0:off) */
+static matrix_row_t matrix[MATRIX_ROWS];
+static matrix_row_t matrix_debouncing[MATRIX_ROWS];
+
+static matrix_row_t read_cols(void);
+static void init_cols(void);
+static void unselect_rows(void);
+static void select_row(uint8_t row);
+
+__attribute__ ((weak))
+void matrix_init_quantum(void) {
+    matrix_init_kb();
+}
+
+__attribute__ ((weak))
+void matrix_scan_quantum(void) {
+    matrix_scan_kb();
+}
+
+__attribute__ ((weak))
+void matrix_init_kb(void) {
+    matrix_init_user();
+}
+
+__attribute__ ((weak))
+void matrix_scan_kb(void) {
+    matrix_scan_user();
+}
+
+__attribute__ ((weak))
+void matrix_init_user(void) {
+}
+
+__attribute__ ((weak))
+void matrix_scan_user(void) {
+}
+
+inline
+uint8_t matrix_rows(void)
+{
+    return MATRIX_ROWS;
+}
+
+inline
+uint8_t matrix_cols(void)
+{
+    return MATRIX_COLS;
+}
+
+void matrix_init(void)
+{
+    debug_enable = true;
+    debug_matrix = true;
+    debug_mouse = true;
+    // initialize row and col
+    unselect_rows();
+    init_cols();
+
+    TX_RX_LED_INIT;
+
+    // initialize matrix state: all keys off
+    for (uint8_t i=0; i < MATRIX_ROWS; i++) {
+        matrix[i] = 0;
+        matrix_debouncing[i] = 0;
+    }
+
+    matrix_init_quantum();
+}
+
+uint8_t _matrix_scan(void)
+{
+    // Right hand is stored after the left in the matirx so, we need to offset it
+    int offset = isLeftHand ? 0 : (ROWS_PER_HAND);
+
+    for (uint8_t i = 0; i < ROWS_PER_HAND; i++) {
+        select_row(i);
+        _delay_us(30);  // without this wait read unstable value.
+        matrix_row_t cols = read_cols();
+        if (matrix_debouncing[i+offset] != cols) {
+            matrix_debouncing[i+offset] = cols;
+            debouncing = DEBOUNCE;
+        }
+        unselect_rows();
+    }
+
+    if (debouncing) {
+        if (--debouncing) {
+            _delay_ms(1);
+        } else {
+            for (uint8_t i = 0; i < ROWS_PER_HAND; i++) {
+                matrix[i+offset] = matrix_debouncing[i+offset];
+            }
+        }
+    }
+
+    return 1;
+}
+
+// Get rows from other half over i2c
+int i2c_transaction(void) {
+    int slaveOffset = (isLeftHand) ? (ROWS_PER_HAND) : 0;
+
+    int err = i2c_master_start(SLAVE_I2C_ADDRESS + I2C_WRITE);
+    if (err) goto i2c_error;
+
+    // start of matrix stored at 0x00
+    err = i2c_master_write(0x00);
+    if (err) goto i2c_error;
+
+    // Start read
+    err = i2c_master_start(SLAVE_I2C_ADDRESS + I2C_READ);
+    if (err) goto i2c_error;
+
+    if (!err) {
+        int i;
+        for (i = 0; i < ROWS_PER_HAND-1; ++i) {
+            matrix[slaveOffset+i] = i2c_master_read(I2C_ACK);
+        }
+        matrix[slaveOffset+i] = i2c_master_read(I2C_NACK);
+        i2c_master_stop();
+    } else {
+i2c_error: // the cable is disconnceted, or something else went wrong
+        i2c_reset_state();
+        return err;
+    }
+
+    return 0;
+}
+
+#ifndef USE_I2C
+int serial_transaction(void) {
+    int slaveOffset = (isLeftHand) ? (ROWS_PER_HAND) : 0;
+
+    if (serial_update_buffers()) {
+        return 1;
+    }
+
+    for (int i = 0; i < ROWS_PER_HAND; ++i) {
+        matrix[slaveOffset+i] = serial_slave_buffer[i];
+    }
+    return 0;
+}
+#endif
+
+uint8_t matrix_scan(void)
+{
+    int ret = _matrix_scan();
+
+
+
+#ifdef USE_I2C
+    if( i2c_transaction() ) {
+#else
+    if( serial_transaction() ) {
+#endif
+        // turn on the indicator led when halves are disconnected
+        TXLED1;
+
+        error_count++;
+
+        if (error_count > ERROR_DISCONNECT_COUNT) {
+            // reset other half if disconnected
+            int slaveOffset = (isLeftHand) ? (ROWS_PER_HAND) : 0;
+            for (int i = 0; i < ROWS_PER_HAND; ++i) {
+                matrix[slaveOffset+i] = 0;
+            }
+        }
+    } else {
+        // turn off the indicator led on no error
+        TXLED0;
+        error_count = 0;
+    }
+
+    matrix_scan_quantum();
+
+    return ret;
+}
+
+void matrix_slave_scan(void) {
+    _matrix_scan();
+
+    int offset = (isLeftHand) ? 0 : (MATRIX_ROWS / 2);
+
+#ifdef USE_I2C
+    for (int i = 0; i < ROWS_PER_HAND; ++i) {
+        /* i2c_slave_buffer[i] = matrix[offset+i]; */
+        i2c_slave_buffer[i] = matrix[offset+i];
+    }
+#else
+    for (int i = 0; i < ROWS_PER_HAND; ++i) {
+        serial_slave_buffer[i] = matrix[offset+i];
+    }
+#endif
+}
+
+bool matrix_is_modified(void)
+{
+    if (debouncing) return false;
+    return true;
+}
+
+inline
+bool matrix_is_on(uint8_t row, uint8_t col)
+{
+    return (matrix[row] & ((matrix_row_t)1<<col));
+}
+
+inline
+matrix_row_t matrix_get_row(uint8_t row)
+{
+    return matrix[row];
+}
+
+void matrix_print(void)
+{
+    print("\nr/c 0123456789ABCDEF\n");
+    for (uint8_t row = 0; row < MATRIX_ROWS; row++) {
+        phex(row); print(": ");
+        pbin_reverse16(matrix_get_row(row));
+        print("\n");
+    }
+}
+
+uint8_t matrix_key_count(void)
+{
+    uint8_t count = 0;
+    for (uint8_t i = 0; i < MATRIX_ROWS; i++) {
+        count += bitpop16(matrix[i]);
+    }
+    return count;
+}
+
+static void  init_cols(void)
+{
+    for(int x = 0; x < MATRIX_COLS; x++) {
+        _SFR_IO8((col_pins[x] >> 4) + 1) &=  ~_BV(col_pins[x] & 0xF);
+        _SFR_IO8((col_pins[x] >> 4) + 2) |= _BV(col_pins[x] & 0xF);
+    }
+}
+
+static matrix_row_t read_cols(void)
+{
+    matrix_row_t result = 0;
+    for(int x = 0; x < MATRIX_COLS; x++) {     
+        result |= (_SFR_IO8(col_pins[x] >> 4) & _BV(col_pins[x] & 0xF)) ? 0 : (1 << x);
+    }
+    return result;
+}
+
+static void unselect_rows(void)
+{
+    for(int x = 0; x < ROWS_PER_HAND; x++) { 
+        _SFR_IO8((row_pins[x] >> 4) + 1) &=  ~_BV(row_pins[x] & 0xF);
+        _SFR_IO8((row_pins[x] >> 4) + 2) |= _BV(row_pins[x] & 0xF);
+    }
+}
+
+static void select_row(uint8_t row)
+{
+    _SFR_IO8((row_pins[row] >> 4) + 1) |=  _BV(row_pins[row] & 0xF);
+    _SFR_IO8((row_pins[row] >> 4) + 2) &= ~_BV(row_pins[row] & 0xF);
+}
diff --git a/keyboards/lets_split/pro_micro.h b/keyboards/lets_split/pro_micro.h
new file mode 100644
index 000000000..09e219b7b
--- /dev/null
+++ b/keyboards/lets_split/pro_micro.h
@@ -0,0 +1,362 @@
+/*
+  pins_arduino.h - Pin definition functions for Arduino
+  Part of Arduino - http://www.arduino.cc/
+
+  Copyright (c) 2007 David A. Mellis
+
+  This library is free software; you can redistribute it and/or
+  modify it under the terms of the GNU Lesser General Public
+  License as published by the Free Software Foundation; either
+  version 2.1 of the License, or (at your option) any later version.
+
+  This library 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
+  Lesser General Public License for more details.
+
+  You should have received a copy of the GNU Lesser General
+  Public License along with this library; if not, write to the
+  Free Software Foundation, Inc., 59 Temple Place, Suite 330,
+  Boston, MA  02111-1307  USA
+
+  $Id: wiring.h 249 2007-02-03 16:52:51Z mellis $
+*/
+
+#ifndef Pins_Arduino_h
+#define Pins_Arduino_h
+
+#include <avr/pgmspace.h>
+
+// Workaround for wrong definitions in "iom32u4.h".
+// This should be fixed in the AVR toolchain.
+#undef UHCON
+#undef UHINT
+#undef UHIEN
+#undef UHADDR
+#undef UHFNUM
+#undef UHFNUML
+#undef UHFNUMH
+#undef UHFLEN
+#undef UPINRQX
+#undef UPINTX
+#undef UPNUM
+#undef UPRST
+#undef UPCONX
+#undef UPCFG0X
+#undef UPCFG1X
+#undef UPSTAX
+#undef UPCFG2X
+#undef UPIENX
+#undef UPDATX
+#undef TCCR2A
+#undef WGM20
+#undef WGM21
+#undef COM2B0
+#undef COM2B1
+#undef COM2A0
+#undef COM2A1
+#undef TCCR2B
+#undef CS20
+#undef CS21
+#undef CS22
+#undef WGM22
+#undef FOC2B
+#undef FOC2A
+#undef TCNT2
+#undef TCNT2_0
+#undef TCNT2_1
+#undef TCNT2_2
+#undef TCNT2_3
+#undef TCNT2_4
+#undef TCNT2_5
+#undef TCNT2_6
+#undef TCNT2_7
+#undef OCR2A
+#undef OCR2_0
+#undef OCR2_1
+#undef OCR2_2
+#undef OCR2_3
+#undef OCR2_4
+#undef OCR2_5
+#undef OCR2_6
+#undef OCR2_7
+#undef OCR2B
+#undef OCR2_0
+#undef OCR2_1
+#undef OCR2_2
+#undef OCR2_3
+#undef OCR2_4
+#undef OCR2_5
+#undef OCR2_6
+#undef OCR2_7
+
+#define NUM_DIGITAL_PINS  30
+#define NUM_ANALOG_INPUTS 12
+
+#define TX_RX_LED_INIT  DDRD |= (1<<5), DDRB |= (1<<0)
+#define TXLED0          PORTD |= (1<<5)
+#define TXLED1          PORTD &= ~(1<<5)
+#define RXLED0          PORTB |= (1<<0)
+#define RXLED1          PORTB &= ~(1<<0)
+
+static const uint8_t SDA = 2;
+static const uint8_t SCL = 3;
+#define LED_BUILTIN 13
+
+// Map SPI port to 'new' pins D14..D17
+static const uint8_t SS   = 17;
+static const uint8_t MOSI = 16;
+static const uint8_t MISO = 14;
+static const uint8_t SCK  = 15;
+
+// Mapping of analog pins as digital I/O
+// A6-A11 share with digital pins
+static const uint8_t A0 = 18;
+static const uint8_t A1 = 19;
+static const uint8_t A2 = 20;
+static const uint8_t A3 = 21;
+static const uint8_t A4 = 22;
+static const uint8_t A5 = 23;
+static const uint8_t A6 = 24;   // D4
+static const uint8_t A7 = 25;   // D6
+static const uint8_t A8 = 26;   // D8
+static const uint8_t A9 = 27;   // D9
+static const uint8_t A10 = 28;  // D10
+static const uint8_t A11 = 29;  // D12
+
+#define digitalPinToPCICR(p)    ((((p) >= 8 && (p) <= 11) || ((p) >= 14 && (p) <= 17) || ((p) >= A8 && (p) <= A10)) ? (&PCICR) : ((uint8_t *)0))
+#define digitalPinToPCICRbit(p) 0
+#define digitalPinToPCMSK(p)    ((((p) >= 8 && (p) <= 11) || ((p) >= 14 && (p) <= 17) || ((p) >= A8 && (p) <= A10)) ? (&PCMSK0) : ((uint8_t *)0))
+#define digitalPinToPCMSKbit(p) ( ((p) >= 8 && (p) <= 11) ? (p) - 4 : ((p) == 14 ? 3 : ((p) == 15 ? 1 : ((p) == 16 ? 2 : ((p) == 17 ? 0 : (p - A8 + 4))))))
+
+//  __AVR_ATmega32U4__ has an unusual mapping of pins to channels
+extern const uint8_t PROGMEM analog_pin_to_channel_PGM[];
+#define analogPinToChannel(P)  ( pgm_read_byte( analog_pin_to_channel_PGM + (P) ) )
+
+#define digitalPinToInterrupt(p) ((p) == 0 ? 2 : ((p) == 1 ? 3 : ((p) == 2 ? 1 : ((p) == 3 ? 0 : ((p) == 7 ? 4 : NOT_AN_INTERRUPT)))))
+
+#ifdef ARDUINO_MAIN
+
+// On the Arduino board, digital pins are also used
+// for the analog output (software PWM).  Analog input
+// pins are a separate set.
+
+// ATMEL ATMEGA32U4 / ARDUINO LEONARDO
+//
+// D0               PD2                 RXD1/INT2
+// D1               PD3                 TXD1/INT3
+// D2               PD1     SDA         SDA/INT1
+// D3#              PD0     PWM8/SCL    OC0B/SCL/INT0
+// D4       A6      PD4                 ADC8
+// D5#              PC6     ???         OC3A/#OC4A
+// D6#      A7      PD7     FastPWM     #OC4D/ADC10
+// D7               PE6                 INT6/AIN0
+//
+// D8       A8      PB4                 ADC11/PCINT4
+// D9#      A9      PB5     PWM16       OC1A/#OC4B/ADC12/PCINT5
+// D10#     A10     PB6     PWM16       OC1B/0c4B/ADC13/PCINT6
+// D11#             PB7     PWM8/16     0C0A/OC1C/#RTS/PCINT7
+// D12      A11     PD6                 T1/#OC4D/ADC9
+// D13#             PC7     PWM10       CLK0/OC4A
+//
+// A0       D18     PF7                 ADC7
+// A1       D19     PF6                 ADC6
+// A2       D20     PF5                 ADC5
+// A3       D21     PF4                 ADC4
+// A4       D22     PF1                 ADC1
+// A5       D23     PF0                 ADC0
+//
+// New pins D14..D17 to map SPI port to digital pins
+//
+// MISO     D14     PB3                 MISO,PCINT3
+// SCK      D15     PB1                 SCK,PCINT1
+// MOSI     D16     PB2                 MOSI,PCINT2
+// SS       D17     PB0                 RXLED,SS/PCINT0
+//
+// Connected LEDs on board for TX and RX
+// TXLED    D24     PD5                 XCK1
+// RXLED    D17     PB0
+// HWB              PE2                 HWB
+
+// these arrays map port names (e.g. port B) to the
+// appropriate addresses for various functions (e.g. reading
+// and writing)
+const uint16_t PROGMEM port_to_mode_PGM[] = {
+    NOT_A_PORT,
+    NOT_A_PORT,
+    (uint16_t) &DDRB,
+    (uint16_t) &DDRC,
+    (uint16_t) &DDRD,
+    (uint16_t) &DDRE,
+    (uint16_t) &DDRF,
+};
+
+const uint16_t PROGMEM port_to_output_PGM[] = {
+    NOT_A_PORT,
+    NOT_A_PORT,
+    (uint16_t) &PORTB,
+    (uint16_t) &PORTC,
+    (uint16_t) &PORTD,
+    (uint16_t) &PORTE,
+    (uint16_t) &PORTF,
+};
+
+const uint16_t PROGMEM port_to_input_PGM[] = {
+    NOT_A_PORT,
+    NOT_A_PORT,
+    (uint16_t) &PINB,
+    (uint16_t) &PINC,
+    (uint16_t) &PIND,
+    (uint16_t) &PINE,
+    (uint16_t) &PINF,
+};
+
+const uint8_t PROGMEM digital_pin_to_port_PGM[] = {
+    PD, // D0 - PD2
+    PD, // D1 - PD3
+    PD, // D2 - PD1
+    PD, // D3 - PD0
+    PD, // D4 - PD4
+    PC, // D5 - PC6
+    PD, // D6 - PD7
+    PE, // D7 - PE6
+    
+    PB, // D8 - PB4
+    PB, // D9 - PB5
+    PB, // D10 - PB6
+    PB, // D11 - PB7
+    PD, // D12 - PD6
+    PC, // D13 - PC7
+    
+    PB, // D14 - MISO - PB3
+    PB, // D15 - SCK - PB1
+    PB, // D16 - MOSI - PB2
+    PB, // D17 - SS - PB0
+    
+    PF, // D18 - A0 - PF7
+    PF, // D19 - A1 - PF6
+    PF, // D20 - A2 - PF5
+    PF, // D21 - A3 - PF4
+    PF, // D22 - A4 - PF1
+    PF, // D23 - A5 - PF0
+    
+    PD, // D24 - PD5
+    PD, // D25 / D6 - A7 - PD7
+    PB, // D26 / D8 - A8 - PB4
+    PB, // D27 / D9 - A9 - PB5
+    PB, // D28 / D10 - A10 - PB6
+    PD, // D29 / D12 - A11 - PD6
+};
+
+const uint8_t PROGMEM digital_pin_to_bit_mask_PGM[] = {
+    _BV(2), // D0 - PD2
+    _BV(3), // D1 - PD3
+    _BV(1), // D2 - PD1
+    _BV(0), // D3 - PD0
+    _BV(4), // D4 - PD4
+    _BV(6), // D5 - PC6
+    _BV(7), // D6 - PD7
+    _BV(6), // D7 - PE6
+    
+    _BV(4), // D8 - PB4
+    _BV(5), // D9 - PB5
+    _BV(6), // D10 - PB6
+    _BV(7), // D11 - PB7
+    _BV(6), // D12 - PD6
+    _BV(7), // D13 - PC7
+    
+    _BV(3), // D14 - MISO - PB3
+    _BV(1), // D15 - SCK - PB1
+    _BV(2), // D16 - MOSI - PB2
+    _BV(0), // D17 - SS - PB0
+    
+    _BV(7), // D18 - A0 - PF7
+    _BV(6), // D19 - A1 - PF6
+    _BV(5), // D20 - A2 - PF5
+    _BV(4), // D21 - A3 - PF4
+    _BV(1), // D22 - A4 - PF1
+    _BV(0), // D23 - A5 - PF0
+    
+    _BV(5), // D24 - PD5
+    _BV(7), // D25 / D6 - A7 - PD7
+    _BV(4), // D26 / D8 - A8 - PB4
+    _BV(5), // D27 / D9 - A9 - PB5
+    _BV(6), // D28 / D10 - A10 - PB6
+    _BV(6), // D29 / D12 - A11 - PD6
+};
+
+const uint8_t PROGMEM digital_pin_to_timer_PGM[] = {
+    NOT_ON_TIMER,   
+    NOT_ON_TIMER,
+    NOT_ON_TIMER,
+    TIMER0B,        /* 3 */
+    NOT_ON_TIMER,
+    TIMER3A,        /* 5 */
+    TIMER4D,        /* 6 */
+    NOT_ON_TIMER,   
+    
+    NOT_ON_TIMER,   
+    TIMER1A,        /* 9 */
+    TIMER1B,        /* 10 */
+    TIMER0A,        /* 11 */
+    
+    NOT_ON_TIMER,   
+    TIMER4A,        /* 13 */
+    
+    NOT_ON_TIMER,   
+    NOT_ON_TIMER,
+    NOT_ON_TIMER,
+    NOT_ON_TIMER,
+    NOT_ON_TIMER,
+    NOT_ON_TIMER,
+
+    NOT_ON_TIMER,
+    NOT_ON_TIMER,
+    NOT_ON_TIMER,
+    NOT_ON_TIMER,
+    NOT_ON_TIMER,
+    NOT_ON_TIMER,
+    NOT_ON_TIMER,
+    NOT_ON_TIMER,
+    NOT_ON_TIMER,
+    NOT_ON_TIMER,
+};
+
+const uint8_t PROGMEM analog_pin_to_channel_PGM[] = {
+    7,  // A0               PF7                 ADC7
+    6,  // A1               PF6                 ADC6    
+    5,  // A2               PF5                 ADC5    
+    4,  // A3               PF4                 ADC4
+    1,  // A4               PF1                 ADC1    
+    0,  // A5               PF0                 ADC0    
+    8,  // A6       D4      PD4                 ADC8
+    10, // A7       D6      PD7                 ADC10
+    11, // A8       D8      PB4                 ADC11
+    12, // A9       D9      PB5                 ADC12
+    13, // A10      D10     PB6                 ADC13
+    9   // A11      D12     PD6                 ADC9
+};
+
+#endif /* ARDUINO_MAIN */
+
+// These serial port names are intended to allow libraries and architecture-neutral
+// sketches to automatically default to the correct port name for a particular type
+// of use.  For example, a GPS module would normally connect to SERIAL_PORT_HARDWARE_OPEN,
+// the first hardware serial port whose RX/TX pins are not dedicated to another use.
+//
+// SERIAL_PORT_MONITOR        Port which normally prints to the Arduino Serial Monitor
+//
+// SERIAL_PORT_USBVIRTUAL     Port which is USB virtual serial
+//
+// SERIAL_PORT_LINUXBRIDGE    Port which connects to a Linux system via Bridge library
+//
+// SERIAL_PORT_HARDWARE       Hardware serial port, physical RX & TX pins.
+//
+// SERIAL_PORT_HARDWARE_OPEN  Hardware serial ports which are open for use.  Their RX & TX
+//                            pins are NOT connected to anything by default.
+#define SERIAL_PORT_MONITOR        Serial
+#define SERIAL_PORT_USBVIRTUAL     Serial
+#define SERIAL_PORT_HARDWARE       Serial1
+#define SERIAL_PORT_HARDWARE_OPEN  Serial1
+
+#endif /* Pins_Arduino_h */
diff --git a/keyboards/lets-split/readme.md b/keyboards/lets_split/readme.md
index e69de29bb..e69de29bb 100644
--- a/keyboards/lets-split/readme.md
+++ b/keyboards/lets_split/readme.md
diff --git a/keyboards/lets_split/split_util.c b/keyboards/lets_split/split_util.c
new file mode 100644
index 000000000..c394596e0
--- /dev/null
+++ b/keyboards/lets_split/split_util.c
@@ -0,0 +1,67 @@
+#include <avr/io.h>
+#include <avr/wdt.h>
+#include <avr/power.h>
+#include <avr/interrupt.h>
+#include <util/delay.h>
+#include <avr/eeprom.h>
+#include "split_util.h"
+#include "matrix.h"
+#include "i2c.h"
+#include "keyboard.h"
+#include "config.h"
+
+volatile bool isLeftHand = true;
+
+static void setup_handedness(void) {
+    isLeftHand = eeprom_read_byte(EECONFIG_HANDEDNESS);
+}
+
+static void keyboard_master_setup(void) {
+#ifdef USE_I2C
+    i2c_master_init();
+#else
+    serial_master_init();
+#endif
+}
+
+static void keyboard_slave_setup(void) {
+#ifdef USE_I2C
+    i2c_slave_init(SLAVE_I2C_ADDRESS);
+#else
+    serial_slave_init();
+#endif
+}
+
+bool has_usb(void) {
+   USBCON |= (1 << OTGPADE); //enables VBUS pad
+   _delay_us(5);
+   return (USBSTA & (1<<VBUS));  //checks state of VBUS
+}
+
+void split_keyboard_setup(void) {
+   setup_handedness();
+
+   if (has_usb()) {
+      keyboard_master_setup();
+   } else {
+      keyboard_slave_setup();
+   }
+   sei();
+}
+
+void keyboard_slave_loop(void) {
+   matrix_init();
+
+   while (1) {
+      matrix_slave_scan();
+   }
+}
+
+// this code runs before the usb and keyboard is initialized
+void matrix_setup(void) {
+    split_keyboard_setup();
+
+    if (!has_usb()) {
+        keyboard_slave_loop();
+    }
+}
diff --git a/keyboards/lets_split/split_util.h b/keyboards/lets_split/split_util.h
new file mode 100644
index 000000000..cf6890d37
--- /dev/null
+++ b/keyboards/lets_split/split_util.h
@@ -0,0 +1,20 @@
+#ifndef SPLIT_KEYBOARD_UTIL_H
+#define SPLIT_KEYBOARD_UTIL_H
+
+#include <stdbool.h>
+
+#define EECONFIG_BOOTMAGIC_END      (uint8_t *)10
+#define EECONFIG_HANDEDNESS         EECONFIG_BOOTMAGIC_END
+
+#define SLAVE_I2C_ADDRESS           0x32
+
+extern volatile bool isLeftHand;
+
+// slave version of matix scan, defined in matrix.c
+void matrix_slave_scan(void);
+
+void split_keyboard_setup(void);
+bool has_usb(void);
+void keyboard_slave_loop(void);
+
+#endif
diff --git a/keyboards/lets_split/uno-slave/Makefile b/keyboards/lets_split/uno-slave/Makefile
new file mode 100644
index 000000000..84e67de11
--- /dev/null
+++ b/keyboards/lets_split/uno-slave/Makefile
@@ -0,0 +1,226 @@
+# Hey Emacs, this is a -*- makefile -*-
+
+# AVR-GCC Makefile template, derived from the WinAVR template (which
+# is public domain), believed to be neutral to any flavor of "make"
+# (GNU make, BSD make, SysV make)
+
+
+MCU = atmega328p
+FORMAT = ihex
+TARGET = keyboard-i2c-slave
+SRC = \
+        $(TARGET).c \
+        uno-matrix.c \
+        ../serial.c \
+        ../i2c-slave.c
+
+ASRC =
+OPT = s
+
+# Programming support using avrdude. Settings and variables.
+
+AVRDUDE_PROGRAMMER = arduino
+AVRDUDE_PORT = /dev/ttyACM0
+
+# Name of this Makefile (used for "make depend").
+MAKEFILE = Makefile
+
+# Debugging format.
+# Native formats for AVR-GCC's -g are stabs [default], or dwarf-2.
+# AVR (extended) COFF requires stabs, plus an avr-objcopy run.
+DEBUG = stabs
+
+# Compiler flag to set the C Standard level.
+# c89   - "ANSI" C
+# gnu89 - c89 plus GCC extensions
+# c99   - ISO C99 standard (not yet fully implemented)
+# gnu99 - c99 plus GCC extensions
+CSTANDARD = -std=gnu99
+
+# Place -D or -U options here
+CDEFS =
+
+# Place -I options here
+CINCS =
+
+
+CDEBUG = -g$(DEBUG)
+CWARN = -Wall -Wstrict-prototypes
+CTUNING = -funsigned-char -funsigned-bitfields -fpack-struct -fshort-enums
+#CEXTRA = -Wa,-adhlns=$(<:.c=.lst)
+CFLAGS = $(CDEBUG) $(CDEFS) $(CINCS) -O$(OPT) $(CWARN) $(CSTANDARD) $(CEXTRA) \
+        -fno-aggressive-loop-optimizations
+
+#ASFLAGS = -Wa,-adhlns=$(<:.S=.lst),-gstabs
+
+
+#Additional libraries.
+
+# Minimalistic printf version
+PRINTF_LIB_MIN = -Wl,-u,vfprintf -lprintf_min
+
+# Floating point printf version (requires MATH_LIB = -lm below)
+PRINTF_LIB_FLOAT = -Wl,-u,vfprintf -lprintf_flt
+
+PRINTF_LIB =
+
+# Minimalistic scanf version
+SCANF_LIB_MIN = -Wl,-u,vfscanf -lscanf_min
+
+# Floating point + %[ scanf version (requires MATH_LIB = -lm below)
+SCANF_LIB_FLOAT = -Wl,-u,vfscanf -lscanf_flt
+
+SCANF_LIB =
+
+MATH_LIB = -lm
+
+# External memory options
+
+# 64 KB of external RAM, starting after internal RAM (ATmega128!),
+# used for variables (.data/.bss) and heap (malloc()).
+#EXTMEMOPTS = -Wl,--section-start,.data=0x801100,--defsym=__heap_end=0x80ffff
+
+# 64 KB of external RAM, starting after internal RAM (ATmega128!),
+# only used for heap (malloc()).
+#EXTMEMOPTS = -Wl,--defsym=__heap_start=0x801100,--defsym=__heap_end=0x80ffff
+
+EXTMEMOPTS =
+
+#LDMAP = $(LDFLAGS) -Wl,-Map=$(TARGET).map,--cref
+LDFLAGS = $(EXTMEMOPTS) $(LDMAP) $(PRINTF_LIB) $(SCANF_LIB) $(MATH_LIB)
+
+
+AVRDUDE_WRITE_FLASH = -U flash:w:$(TARGET).hex
+#AVRDUDE_WRITE_EEPROM = -U eeprom:w:$(TARGET).eep
+
+
+# Uncomment the following if you want avrdude's erase cycle counter.
+# Note that this counter needs to be initialized first using -Yn,
+# see avrdude manual.
+#AVRDUDE_ERASE_COUNTER = -y
+
+# Uncomment the following if you do /not/ wish a verification to be
+# performed after programming the device.
+#AVRDUDE_NO_VERIFY = -V
+
+# Increase verbosity level.  Please use this when submitting bug
+# reports about avrdude. See <http://savannah.nongnu.org/projects/avrdude>
+# to submit bug reports.
+#AVRDUDE_VERBOSE = -v -v
+
+AVRDUDE_BASIC = -p $(MCU) -P $(AVRDUDE_PORT) -c $(AVRDUDE_PROGRAMMER)
+AVRDUDE_FLAGS = $(AVRDUDE_BASIC) $(AVRDUDE_NO_VERIFY) $(AVRDUDE_VERBOSE) $(AVRDUDE_ERASE_COUNTER)
+
+
+CC = avr-gcc
+OBJCOPY = avr-objcopy
+OBJDUMP = avr-objdump
+SIZE = avr-size
+NM = avr-nm
+AVRDUDE = avrdude
+REMOVE = rm -f
+MV = mv -f
+
+# Define all object files.
+OBJ = $(SRC:.c=.o) $(ASRC:.S=.o)
+
+# Define all listing files.
+LST = $(ASRC:.S=.lst) $(SRC:.c=.lst)
+
+# Combine all necessary flags and optional flags.
+# Add target processor to flags.
+ALL_CFLAGS = -mmcu=$(MCU) -I. $(CFLAGS)
+ALL_ASFLAGS = -mmcu=$(MCU) -I. -x assembler-with-cpp $(ASFLAGS)
+
+
+# Default target.
+all: build
+
+build: elf hex eep
+
+elf: $(TARGET).elf
+hex: $(TARGET).hex
+eep: $(TARGET).eep
+lss: $(TARGET).lss
+sym: $(TARGET).sym
+
+
+# Program the device.
+program: $(TARGET).hex $(TARGET).eep
+        $(AVRDUDE) $(AVRDUDE_FLAGS) $(AVRDUDE_WRITE_FLASH) $(AVRDUDE_WRITE_EEPROM)
+
+
+# Convert ELF to COFF for use in debugging / simulating in AVR Studio or VMLAB.
+COFFCONVERT=$(OBJCOPY) --debugging \
+--change-section-address .data-0x800000 \
+--change-section-address .bss-0x800000 \
+--change-section-address .noinit-0x800000 \
+--change-section-address .eeprom-0x810000
+
+
+coff: $(TARGET).elf
+        $(COFFCONVERT) -O coff-avr $(TARGET).elf $(TARGET).cof
+
+
+extcoff: $(TARGET).elf
+        $(COFFCONVERT) -O coff-ext-avr $(TARGET).elf $(TARGET).cof
+
+
+.SUFFIXES: .elf .hex .eep .lss .sym
+
+.elf.hex:
+        $(OBJCOPY) -O $(FORMAT) -R .eeprom $< $@
+
+.elf.eep:
+        -$(OBJCOPY) -j .eeprom --set-section-flags=.eeprom="alloc,load" \
+        --change-section-lma .eeprom=0 -O $(FORMAT) $< $@
+
+# Create extended listing file from ELF output file.
+.elf.lss:
+        $(OBJDUMP) -h -S $< > $@
+
+# Create a symbol table from ELF output file.
+.elf.sym:
+        $(NM) -n $< > $@
+
+
+
+# Link: create ELF output file from object files.
+$(TARGET).elf: $(OBJ)
+        $(CC) $(ALL_CFLAGS) $(OBJ) --output $@ $(LDFLAGS)
+
+
+# Compile: create object files from C source files.
+.c.o:
+        $(CC) -c $(ALL_CFLAGS) $< -o $@
+
+
+# Compile: create assembler files from C source files.
+.c.s:
+        $(CC) -S $(ALL_CFLAGS) $< -o $@
+
+
+# Assemble: create object files from assembler source files.
+.S.o:
+        $(CC) -c $(ALL_ASFLAGS) $< -o $@
+
+
+
+# Target: clean project.
+clean:
+        $(REMOVE) $(TARGET).hex $(TARGET).eep $(TARGET).cof $(TARGET).elf \
+        $(TARGET).map $(TARGET).sym $(TARGET).lss \
+        $(OBJ) $(LST) $(SRC:.c=.s) $(SRC:.c=.d)
+
+depend:
+        if grep '^# DO NOT DELETE' $(MAKEFILE) >/dev/null; \
+        then \
+                sed -e '/^# DO NOT DELETE/,$$d' $(MAKEFILE) > \
+                        $(MAKEFILE).$$$$ && \
+                $(MV) $(MAKEFILE).$$$$ $(MAKEFILE); \
+        fi
+        echo '# DO NOT DELETE THIS LINE -- make depend depends on it.' \
+                >> $(MAKEFILE); \
+        $(CC) -M -mmcu=$(MCU) $(CDEFS) $(CINCS) $(SRC) $(ASRC) >> $(MAKEFILE)
+
+.PHONY: all build elf hex eep lss sym program coff extcoff clean depend
diff --git a/keyboards/lets_split/uno-slave/keyboard-i2c-slave.c b/keyboards/lets_split/uno-slave/keyboard-i2c-slave.c
new file mode 100644
index 000000000..2043e7b94
--- /dev/null
+++ b/keyboards/lets_split/uno-slave/keyboard-i2c-slave.c
@@ -0,0 +1,42 @@
+#include "../i2c-slave.h"
+#include "../serial.h"
+#include "uno-matrix.h"
+
+#include <avr/io.h>
+#include <avr/interrupt.h>
+#include <util/delay.h>
+
+void setup(void) {
+  // give some time for noise to clear
+  _delay_us(1000);
+
+  // turn off arduino uno's led on pin 13
+  DDRB |= (1 << 5);
+  PORTB &= ~(1 << 5);
+
+  matrix_init();
+  /* i2c_slave_init(0x32); */
+  serial_slave_init();
+
+  /* serial_slave_buffer[0] = 0xa1; */
+  /* serial_slave_buffer[1] = 0x52; */
+  /* serial_slave_buffer[2] = 0xa2; */
+  /* serial_slave_buffer[3] = 0x67; */
+
+  // need interrupts for i2c slave code to work
+  sei();
+}
+
+void loop(void) {
+  matrix_scan();
+  for(int i=0; i<MATRIX_ROWS; ++i) {
+    slaveBuffer[i] = matrix_get_row(i);
+    serial_slave_buffer[i] = slaveBuffer[i];
+  }
+}
+
+int main(int argc, char *argv[]) {
+  setup();
+  while (1)
+    loop();
+}
diff --git a/keyboards/lets_split/uno-slave/readme.md b/keyboards/lets_split/uno-slave/readme.md
new file mode 100644
index 000000000..d0f03126c
--- /dev/null
+++ b/keyboards/lets_split/uno-slave/readme.md
@@ -0,0 +1 @@
+Code for Arduino uno (atmega328p) slave used for testing.
diff --git a/keyboards/lets_split/uno-slave/uno-matrix.c b/keyboards/lets_split/uno-slave/uno-matrix.c
new file mode 100644
index 000000000..4ac3c33ac
--- /dev/null
+++ b/keyboards/lets_split/uno-slave/uno-matrix.c
@@ -0,0 +1,160 @@
+#define F_CPU 16000000UL
+
+#include <util/delay.h>
+#include <avr/io.h>
+#include <stdlib.h>
+
+#include "uno-matrix.h"
+
+#define debug(X) NULL
+#define debug_hex(X) NULL
+
+#ifndef DEBOUNCE
+#   define DEBOUNCE  5
+#endif
+
+static uint8_t debouncing = DEBOUNCE;
+
+/* matrix state(1:on, 0:off) */
+static matrix_row_t matrix[MATRIX_ROWS];
+static matrix_row_t matrix_debouncing[MATRIX_ROWS];
+
+static matrix_row_t read_cols(void);
+static void init_cols(void);
+static void unselect_rows(void);
+static void select_row(uint8_t row);
+
+inline
+uint8_t matrix_rows(void)
+{
+    return MATRIX_ROWS;
+}
+
+inline
+uint8_t matrix_cols(void)
+{
+    return MATRIX_COLS;
+}
+
+void matrix_init(void)
+{
+    //debug_enable = true;
+    //debug_matrix = true;
+    //debug_mouse = true;
+    // initialize row and col
+    unselect_rows();
+    init_cols();
+
+    // initialize matrix state: all keys off
+    for (uint8_t i=0; i < MATRIX_ROWS; i++) {
+        matrix[i] = 0;
+        matrix_debouncing[i] = 0;
+    }
+}
+
+uint8_t matrix_scan(void)
+{
+    for (uint8_t i = 0; i < MATRIX_ROWS; i++) {
+        select_row(i);
+        _delay_us(30);  // without this wait read unstable value.
+        matrix_row_t cols = read_cols();
+        //Serial.println(cols, BIN);
+        if (matrix_debouncing[i] != cols) {
+            matrix_debouncing[i] = cols;
+            if (debouncing) {
+                debug("bounce!: "); debug_hex(debouncing); debug("\n");
+            }
+            debouncing = DEBOUNCE;
+        }
+        unselect_rows();
+    }
+
+    if (debouncing) {
+        if (--debouncing) {
+            _delay_ms(1);
+        } else {
+            for (uint8_t i = 0; i < MATRIX_ROWS; i++) {
+                matrix[i] = matrix_debouncing[i];
+            }
+        }
+    }
+
+    return 1;
+}
+
+bool matrix_is_modified(void)
+{
+    if (debouncing) return false;
+    return true;
+}
+
+inline
+bool matrix_is_on(uint8_t row, uint8_t col)
+{
+    return (matrix[row] & ((matrix_row_t)1<<col));
+}
+
+inline
+matrix_row_t matrix_get_row(uint8_t row)
+{
+    return matrix[row];
+}
+
+// TODO update this comment
+/* Column pin configuration
+ * col: 0   1   2   3   4   5
+ * pin: D3  D4  D5  D6  D7  B0
+ */
+static void  init_cols(void)
+{
+    // Input with pull-up(DDR:0, PORT:1)
+  DDRD  &= ~(1<<3 | 1<<4 | 1<<5 | 1<<6 | 1<<7);
+  PORTD |=  (1<<3 | 1<<4 | 1<<5 | 1<<6 | 1<<7);
+
+  DDRB  &= ~(1<<0);
+  PORTB |=  (1<<0);
+}
+
+static matrix_row_t read_cols(void)
+{
+    return (PIND&(1<<3) ? 0 : (1<<0)) |
+           (PIND&(1<<4) ? 0 : (1<<1)) |
+           (PIND&(1<<5) ? 0 : (1<<2)) |
+           (PIND&(1<<6) ? 0 : (1<<3)) |
+           (PIND&(1<<7) ? 0 : (1<<4)) |
+           (PINB&(1<<0) ? 0 : (1<<5));
+}
+
+/* Row pin configuration
+ * row: 0  1  2  3
+ * pin: C0 C1 C2 C3
+ */
+static void unselect_rows(void)
+{
+    // Hi-Z(DDR:0, PORT:0) to unselect
+    DDRC  &= ~0xF;
+    PORTC &= ~0xF;
+}
+
+static void select_row(uint8_t row)
+{
+    // Output low(DDR:1, PORT:0) to select
+    switch (row) {
+        case 0:
+            DDRC  |= (1<<0);
+            PORTC &= ~(1<<0);
+            break;
+        case 1:
+            DDRC  |= (1<<1);
+            PORTC &= ~(1<<1);
+            break;
+        case 2:
+            DDRC  |= (1<<2);
+            PORTC &= ~(1<<2);
+            break;
+        case 3:
+            DDRC  |= (1<<3);
+            PORTC &= ~(1<<3);
+            break;
+    }
+}
diff --git a/keyboards/lets_split/uno-slave/uno-matrix.h b/keyboards/lets_split/uno-slave/uno-matrix.h
new file mode 100644
index 000000000..c0f636f80
--- /dev/null
+++ b/keyboards/lets_split/uno-slave/uno-matrix.h
@@ -0,0 +1,19 @@
+#ifndef UNO_MATRIX
+#define UNO_MATRIX
+
+#define MATRIX_ROWS 4
+#define MATRIX_COLS 6
+
+#include <stdbool.h>
+
+typedef uint8_t matrix_row_t;
+
+uint8_t matrix_rows(void);
+uint8_t matrix_cols(void);
+void matrix_init(void);
+uint8_t matrix_scan(void);
+bool matrix_is_modified(void);
+bool matrix_is_on(uint8_t row, uint8_t col);
+matrix_row_t matrix_get_row(uint8_t row);
+
+#endif
diff --git a/keyboards/lets_split/usbconfig.h b/keyboards/lets_split/usbconfig.h
new file mode 100644
index 000000000..d0ca4c717
--- /dev/null
+++ b/keyboards/lets_split/usbconfig.h
@@ -0,0 +1,377 @@
+/* Name: usbconfig.h
+ * Project: V-USB, virtual USB port for Atmel's(r) AVR(r) microcontrollers
+ * Author: Christian Starkjohann
+ * Creation Date: 2005-04-01
+ * Tabsize: 4
+ * Copyright: (c) 2005 by OBJECTIVE DEVELOPMENT Software GmbH
+ * License: GNU GPL v2 (see License.txt), GNU GPL v3 or proprietary (CommercialLicense.txt)
+ * This Revision: $Id: usbconfig-prototype.h 785 2010-05-30 17:57:07Z cs $
+ */
+
+#ifndef __usbconfig_h_included__
+#define __usbconfig_h_included__
+
+
+/*
+General Description:
+This file is an example configuration (with inline documentation) for the USB
+driver. It configures V-USB for USB D+ connected to Port D bit 2 (which is
+also hardware interrupt 0 on many devices) and USB D- to Port D bit 4. You may
+wire the lines to any other port, as long as D+ is also wired to INT0 (or any
+other hardware interrupt, as long as it is the highest level interrupt, see
+section at the end of this file).
+*/
+
+/* ---------------------------- Hardware Config ---------------------------- */
+
+#define USB_CFG_IOPORTNAME      D
+/* This is the port where the USB bus is connected. When you configure it to
+ * "B", the registers PORTB, PINB and DDRB will be used.
+ */
+#define USB_CFG_DMINUS_BIT      3
+/* This is the bit number in USB_CFG_IOPORT where the USB D- line is connected.
+ * This may be any bit in the port.
+ */
+#define USB_CFG_DPLUS_BIT       2
+/* This is the bit number in USB_CFG_IOPORT where the USB D+ line is connected.
+ * This may be any bit in the port. Please note that D+ must also be connected
+ * to interrupt pin INT0! [You can also use other interrupts, see section
+ * "Optional MCU Description" below, or you can connect D- to the interrupt, as
+ * it is required if you use the USB_COUNT_SOF feature. If you use D- for the
+ * interrupt, the USB interrupt will also be triggered at Start-Of-Frame
+ * markers every millisecond.]
+ */
+#define USB_CFG_CLOCK_KHZ       (F_CPU/1000)
+/* Clock rate of the AVR in kHz. Legal values are 12000, 12800, 15000, 16000,
+ * 16500, 18000 and 20000. The 12.8 MHz and 16.5 MHz versions of the code
+ * require no crystal, they tolerate +/- 1% deviation from the nominal
+ * frequency. All other rates require a precision of 2000 ppm and thus a
+ * crystal!
+ * Since F_CPU should be defined to your actual clock rate anyway, you should
+ * not need to modify this setting.
+ */
+#define USB_CFG_CHECK_CRC       0
+/* Define this to 1 if you want that the driver checks integrity of incoming
+ * data packets (CRC checks). CRC checks cost quite a bit of code size and are
+ * currently only available for 18 MHz crystal clock. You must choose
+ * USB_CFG_CLOCK_KHZ = 18000 if you enable this option.
+ */
+
+/* ----------------------- Optional Hardware Config ------------------------ */
+
+/* #define USB_CFG_PULLUP_IOPORTNAME   D */
+/* If you connect the 1.5k pullup resistor from D- to a port pin instead of
+ * V+, you can connect and disconnect the device from firmware by calling
+ * the macros usbDeviceConnect() and usbDeviceDisconnect() (see usbdrv.h).
+ * This constant defines the port on which the pullup resistor is connected.
+ */
+/* #define USB_CFG_PULLUP_BIT          4 */
+/* This constant defines the bit number in USB_CFG_PULLUP_IOPORT (defined
+ * above) where the 1.5k pullup resistor is connected. See description
+ * above for details.
+ */
+
+/* --------------------------- Functional Range ---------------------------- */
+
+#define USB_CFG_HAVE_INTRIN_ENDPOINT    1
+/* Define this to 1 if you want to compile a version with two endpoints: The
+ * default control endpoint 0 and an interrupt-in endpoint (any other endpoint
+ * number).
+ */
+#define USB_CFG_HAVE_INTRIN_ENDPOINT3   1
+/* Define this to 1 if you want to compile a version with three endpoints: The
+ * default control endpoint 0, an interrupt-in endpoint 3 (or the number
+ * configured below) and a catch-all default interrupt-in endpoint as above.
+ * You must also define USB_CFG_HAVE_INTRIN_ENDPOINT to 1 for this feature.
+ */
+#define USB_CFG_EP3_NUMBER              3
+/* If the so-called endpoint 3 is used, it can now be configured to any other
+ * endpoint number (except 0) with this macro. Default if undefined is 3.
+ */
+/* #define USB_INITIAL_DATATOKEN           USBPID_DATA1 */
+/* The above macro defines the startup condition for data toggling on the
+ * interrupt/bulk endpoints 1 and 3. Defaults to USBPID_DATA1.
+ * Since the token is toggled BEFORE sending any data, the first packet is
+ * sent with the oposite value of this configuration!
+ */
+#define USB_CFG_IMPLEMENT_HALT          0
+/* Define this to 1 if you also want to implement the ENDPOINT_HALT feature
+ * for endpoint 1 (interrupt endpoint). Although you may not need this feature,
+ * it is required by the standard. We have made it a config option because it
+ * bloats the code considerably.
+ */
+#define USB_CFG_SUPPRESS_INTR_CODE      0
+/* Define this to 1 if you want to declare interrupt-in endpoints, but don't
+ * want to send any data over them. If this macro is defined to 1, functions
+ * usbSetInterrupt() and usbSetInterrupt3() are omitted. This is useful if
+ * you need the interrupt-in endpoints in order to comply to an interface
+ * (e.g. HID), but never want to send any data. This option saves a couple
+ * of bytes in flash memory and the transmit buffers in RAM.
+ */
+#define USB_CFG_INTR_POLL_INTERVAL      10
+/* If you compile a version with endpoint 1 (interrupt-in), this is the poll
+ * interval. The value is in milliseconds and must not be less than 10 ms for
+ * low speed devices.
+ */
+#define USB_CFG_IS_SELF_POWERED         0
+/* Define this to 1 if the device has its own power supply. Set it to 0 if the
+ * device is powered from the USB bus.
+ */
+#define USB_CFG_MAX_BUS_POWER           100
+/* Set this variable to the maximum USB bus power consumption of your device.
+ * The value is in milliamperes. [It will be divided by two since USB
+ * communicates power requirements in units of 2 mA.]
+ */
+#define USB_CFG_IMPLEMENT_FN_WRITE      1
+/* Set this to 1 if you want usbFunctionWrite() to be called for control-out
+ * transfers. Set it to 0 if you don't need it and want to save a couple of
+ * bytes.
+ */
+#define USB_CFG_IMPLEMENT_FN_READ       0
+/* Set this to 1 if you need to send control replies which are generated
+ * "on the fly" when usbFunctionRead() is called. If you only want to send
+ * data from a static buffer, set it to 0 and return the data from
+ * usbFunctionSetup(). This saves a couple of bytes.
+ */
+#define USB_CFG_IMPLEMENT_FN_WRITEOUT   0
+/* Define this to 1 if you want to use interrupt-out (or bulk out) endpoints.
+ * You must implement the function usbFunctionWriteOut() which receives all
+ * interrupt/bulk data sent to any endpoint other than 0. The endpoint number
+ * can be found in 'usbRxToken'.
+ */
+#define USB_CFG_HAVE_FLOWCONTROL        0
+/* Define this to 1 if you want flowcontrol over USB data. See the definition
+ * of the macros usbDisableAllRequests() and usbEnableAllRequests() in
+ * usbdrv.h.
+ */
+#define USB_CFG_DRIVER_FLASH_PAGE       0
+/* If the device has more than 64 kBytes of flash, define this to the 64 k page
+ * where the driver's constants (descriptors) are located. Or in other words:
+ * Define this to 1 for boot loaders on the ATMega128.
+ */
+#define USB_CFG_LONG_TRANSFERS          0
+/* Define this to 1 if you want to send/receive blocks of more than 254 bytes
+ * in a single control-in or control-out transfer. Note that the capability
+ * for long transfers increases the driver size.
+ */
+/* #define USB_RX_USER_HOOK(data, len)     if(usbRxToken == (uchar)USBPID_SETUP) blinkLED(); */
+/* This macro is a hook if you want to do unconventional things. If it is
+ * defined, it's inserted at the beginning of received message processing.
+ * If you eat the received message and don't want default processing to
+ * proceed, do a return after doing your things. One possible application
+ * (besides debugging) is to flash a status LED on each packet.
+ */
+/* #define USB_RESET_HOOK(resetStarts)     if(!resetStarts){hadUsbReset();} */
+/* This macro is a hook if you need to know when an USB RESET occurs. It has
+ * one parameter which distinguishes between the start of RESET state and its
+ * end.
+ */
+/* #define USB_SET_ADDRESS_HOOK()              hadAddressAssigned(); */
+/* This macro (if defined) is executed when a USB SET_ADDRESS request was
+ * received.
+ */
+#define USB_COUNT_SOF                   0
+/* define this macro to 1 if you need the global variable "usbSofCount" which
+ * counts SOF packets. This feature requires that the hardware interrupt is
+ * connected to D- instead of D+.
+ */
+/* #ifdef __ASSEMBLER__
+ * macro myAssemblerMacro
+ *     in      YL, TCNT0
+ *     sts     timer0Snapshot, YL
+ *     endm
+ * #endif
+ * #define USB_SOF_HOOK                    myAssemblerMacro
+ * This macro (if defined) is executed in the assembler module when a
+ * Start Of Frame condition is detected. It is recommended to define it to
+ * the name of an assembler macro which is defined here as well so that more
+ * than one assembler instruction can be used. The macro may use the register
+ * YL and modify SREG. If it lasts longer than a couple of cycles, USB messages
+ * immediately after an SOF pulse may be lost and must be retried by the host.
+ * What can you do with this hook? Since the SOF signal occurs exactly every
+ * 1 ms (unless the host is in sleep mode), you can use it to tune OSCCAL in
+ * designs running on the internal RC oscillator.
+ * Please note that Start Of Frame detection works only if D- is wired to the
+ * interrupt, not D+. THIS IS DIFFERENT THAN MOST EXAMPLES!
+ */
+#define USB_CFG_CHECK_DATA_TOGGLING     0
+/* define this macro to 1 if you want to filter out duplicate data packets
+ * sent by the host. Duplicates occur only as a consequence of communication
+ * errors, when the host does not receive an ACK. Please note that you need to
+ * implement the filtering yourself in usbFunctionWriteOut() and
+ * usbFunctionWrite(). Use the global usbCurrentDataToken and a static variable
+ * for each control- and out-endpoint to check for duplicate packets.
+ */
+#define USB_CFG_HAVE_MEASURE_FRAME_LENGTH   0
+/* define this macro to 1 if you want the function usbMeasureFrameLength()
+ * compiled in. This function can be used to calibrate the AVR's RC oscillator.
+ */
+#define USB_USE_FAST_CRC                0
+/* The assembler module has two implementations for the CRC algorithm. One is
+ * faster, the other is smaller. This CRC routine is only used for transmitted
+ * messages where timing is not critical. The faster routine needs 31 cycles
+ * per byte while the smaller one needs 61 to 69 cycles. The faster routine
+ * may be worth the 32 bytes bigger code size if you transmit lots of data and
+ * run the AVR close to its limit.
+ */
+
+/* -------------------------- Device Description --------------------------- */
+
+#define USB_CFG_VENDOR_ID       (VENDOR_ID & 0xFF), ((VENDOR_ID >> 8) & 0xFF)
+/* USB vendor ID for the device, low byte first. If you have registered your
+ * own Vendor ID, define it here. Otherwise you may use one of obdev's free
+ * shared VID/PID pairs. Be sure to read USB-IDs-for-free.txt for rules!
+ * *** IMPORTANT NOTE ***
+ * This template uses obdev's shared VID/PID pair for Vendor Class devices
+ * with libusb: 0x16c0/0x5dc.  Use this VID/PID pair ONLY if you understand
+ * the implications!
+ */
+#define USB_CFG_DEVICE_ID       (PRODUCT_ID & 0xFF), ((PRODUCT_ID >> 8) & 0xFF)
+/* This is the ID of the product, low byte first. It is interpreted in the
+ * scope of the vendor ID. If you have registered your own VID with usb.org
+ * or if you have licensed a PID from somebody else, define it here. Otherwise
+ * you may use one of obdev's free shared VID/PID pairs. See the file
+ * USB-IDs-for-free.txt for details!
+ * *** IMPORTANT NOTE ***
+ * This template uses obdev's shared VID/PID pair for Vendor Class devices
+ * with libusb: 0x16c0/0x5dc.  Use this VID/PID pair ONLY if you understand
+ * the implications!
+ */
+#define USB_CFG_DEVICE_VERSION  0x00, 0x01
+/* Version number of the device: Minor number first, then major number.
+ */
+#define USB_CFG_VENDOR_NAME     't', '.', 'm', '.', 'k', '.'
+#define USB_CFG_VENDOR_NAME_LEN 6
+/* These two values define the vendor name returned by the USB device. The name
+ * must be given as a list of characters under single quotes. The characters
+ * are interpreted as Unicode (UTF-16) entities.
+ * If you don't want a vendor name string, undefine these macros.
+ * ALWAYS define a vendor name containing your Internet domain name if you use
+ * obdev's free shared VID/PID pair. See the file USB-IDs-for-free.txt for
+ * details.
+ */
+#define USB_CFG_DEVICE_NAME     'P', 'S', '/', '2', ' ', 'k', 'e', 'y', 'b', 'o', 'a', 'r', 'd', ' ', 'c', 'o', 'n', 'v', 'e', 'r', 't', 'e', 'r'
+#define USB_CFG_DEVICE_NAME_LEN 23
+/* Same as above for the device name. If you don't want a device name, undefine
+ * the macros. See the file USB-IDs-for-free.txt before you assign a name if
+ * you use a shared VID/PID.
+ */
+/*#define USB_CFG_SERIAL_NUMBER   'N', 'o', 'n', 'e' */
+/*#define USB_CFG_SERIAL_NUMBER_LEN   0 */
+/* Same as above for the serial number. If you don't want a serial number,
+ * undefine the macros.
+ * It may be useful to provide the serial number through other means than at
+ * compile time. See the section about descriptor properties below for how
+ * to fine tune control over USB descriptors such as the string descriptor
+ * for the serial number.
+ */
+#define USB_CFG_DEVICE_CLASS        0
+#define USB_CFG_DEVICE_SUBCLASS     0
+/* See USB specification if you want to conform to an existing device class.
+ * Class 0xff is "vendor specific".
+ */
+#define USB_CFG_INTERFACE_CLASS     3   /* HID */
+#define USB_CFG_INTERFACE_SUBCLASS  1   /* Boot */
+#define USB_CFG_INTERFACE_PROTOCOL  1   /* Keyboard */
+/* See USB specification if you want to conform to an existing device class or
+ * protocol. The following classes must be set at interface level:
+ * HID class is 3, no subclass and protocol required (but may be useful!)
+ * CDC class is 2, use subclass 2 and protocol 1 for ACM
+ */
+#define USB_CFG_HID_REPORT_DESCRIPTOR_LENGTH    0
+/* Define this to the length of the HID report descriptor, if you implement
+ * an HID device. Otherwise don't define it or define it to 0.
+ * If you use this define, you must add a PROGMEM character array named
+ * "usbHidReportDescriptor" to your code which contains the report descriptor.
+ * Don't forget to keep the array and this define in sync!
+ */
+
+/* #define USB_PUBLIC static */
+/* Use the define above if you #include usbdrv.c instead of linking against it.
+ * This technique saves a couple of bytes in flash memory.
+ */
+
+/* ------------------- Fine Control over USB Descriptors ------------------- */
+/* If you don't want to use the driver's default USB descriptors, you can
+ * provide our own. These can be provided as (1) fixed length static data in
+ * flash memory, (2) fixed length static data in RAM or (3) dynamically at
+ * runtime in the function usbFunctionDescriptor(). See usbdrv.h for more
+ * information about this function.
+ * Descriptor handling is configured through the descriptor's properties. If
+ * no properties are defined or if they are 0, the default descriptor is used.
+ * Possible properties are:
+ *   + USB_PROP_IS_DYNAMIC: The data for the descriptor should be fetched
+ *     at runtime via usbFunctionDescriptor(). If the usbMsgPtr mechanism is
+ *     used, the data is in FLASH by default. Add property USB_PROP_IS_RAM if
+ *     you want RAM pointers.
+ *   + USB_PROP_IS_RAM: The data returned by usbFunctionDescriptor() or found
+ *     in static memory is in RAM, not in flash memory.
+ *   + USB_PROP_LENGTH(len): If the data is in static memory (RAM or flash),
+ *     the driver must know the descriptor's length. The descriptor itself is
+ *     found at the address of a well known identifier (see below).
+ * List of static descriptor names (must be declared PROGMEM if in flash):
+ *   char usbDescriptorDevice[];
+ *   char usbDescriptorConfiguration[];
+ *   char usbDescriptorHidReport[];
+ *   char usbDescriptorString0[];
+ *   int usbDescriptorStringVendor[];
+ *   int usbDescriptorStringDevice[];
+ *   int usbDescriptorStringSerialNumber[];
+ * Other descriptors can't be provided statically, they must be provided
+ * dynamically at runtime.
+ *
+ * Descriptor properties are or-ed or added together, e.g.:
+ * #define USB_CFG_DESCR_PROPS_DEVICE   (USB_PROP_IS_RAM | USB_PROP_LENGTH(18))
+ *
+ * The following descriptors are defined:
+ *   USB_CFG_DESCR_PROPS_DEVICE
+ *   USB_CFG_DESCR_PROPS_CONFIGURATION
+ *   USB_CFG_DESCR_PROPS_STRINGS
+ *   USB_CFG_DESCR_PROPS_STRING_0
+ *   USB_CFG_DESCR_PROPS_STRING_VENDOR
+ *   USB_CFG_DESCR_PROPS_STRING_PRODUCT
+ *   USB_CFG_DESCR_PROPS_STRING_SERIAL_NUMBER
+ *   USB_CFG_DESCR_PROPS_HID
+ *   USB_CFG_DESCR_PROPS_HID_REPORT
+ *   USB_CFG_DESCR_PROPS_UNKNOWN (for all descriptors not handled by the driver)
+ *
+ * Note about string descriptors: String descriptors are not just strings, they
+ * are Unicode strings prefixed with a 2 byte header. Example:
+ * int  serialNumberDescriptor[] = {
+ *     USB_STRING_DESCRIPTOR_HEADER(6),
+ *     'S', 'e', 'r', 'i', 'a', 'l'
+ * };
+ */
+
+#define USB_CFG_DESCR_PROPS_DEVICE                  0
+#define USB_CFG_DESCR_PROPS_CONFIGURATION           USB_PROP_IS_DYNAMIC
+//#define USB_CFG_DESCR_PROPS_CONFIGURATION           0
+#define USB_CFG_DESCR_PROPS_STRINGS                 0
+#define USB_CFG_DESCR_PROPS_STRING_0                0
+#define USB_CFG_DESCR_PROPS_STRING_VENDOR           0
+#define USB_CFG_DESCR_PROPS_STRING_PRODUCT          0
+#define USB_CFG_DESCR_PROPS_STRING_SERIAL_NUMBER    0
+//#define USB_CFG_DESCR_PROPS_HID                     USB_PROP_IS_DYNAMIC
+#define USB_CFG_DESCR_PROPS_HID                     0
+#define USB_CFG_DESCR_PROPS_HID_REPORT              USB_PROP_IS_DYNAMIC
+//#define USB_CFG_DESCR_PROPS_HID_REPORT              0
+#define USB_CFG_DESCR_PROPS_UNKNOWN                 0
+
+/* ----------------------- Optional MCU Description ------------------------ */
+
+/* The following configurations have working defaults in usbdrv.h. You
+ * usually don't need to set them explicitly. Only if you want to run
+ * the driver on a device which is not yet supported or with a compiler
+ * which is not fully supported (such as IAR C) or if you use a differnt
+ * interrupt than INT0, you may have to define some of these.
+ */
+/* #define USB_INTR_CFG            MCUCR */
+/* #define USB_INTR_CFG_SET        ((1 << ISC00) | (1 << ISC01)) */
+/* #define USB_INTR_CFG_CLR        0 */
+/* #define USB_INTR_ENABLE         GIMSK */
+/* #define USB_INTR_ENABLE_BIT     INT0 */
+/* #define USB_INTR_PENDING        GIFR */
+/* #define USB_INTR_PENDING_BIT    INTF0 */
+/* #define USB_INTR_VECTOR         INT0_vect */
+
+#endif /* __usbconfig_h_included__ */
diff --git a/tmk_core/common/matrix.h b/tmk_core/common/matrix.h
index 71153a5f5..cee3593ee 100644
--- a/tmk_core/common/matrix.h
+++ b/tmk_core/common/matrix.h
@@ -72,6 +72,11 @@ void matrix_scan_kb(void);
 void matrix_init_user(void);
 void matrix_scan_user(void);
 
+#ifdef I2C_SPLIT
+        void slave_matrix_init(void);
+        uint8_t slave_matrix_scan(void);
+#endif
+
 #ifdef __cplusplus
 }
 #endif