6 files changed, 78 insertions, 37 deletions

diff --git a/bootloader.mk b/bootloader.mk
index 4bcf183fb..9d73063d0 100644
--- a/bootloader.mk
+++ b/bootloader.mk
@@ -76,6 +76,10 @@ ifeq ($(strip $(BOOTLOADER)), bootloadHID)
     OPT_DEFS += -DBOOTLOADER_BOOTLOADHID
     BOOTLOADER_SIZE = 4096
 endif
+ifeq ($(strip $(BOOTLOADER)), USBasp)
+    OPT_DEFS += -DBOOTLOADER_USBASP
+    BOOTLOADER_SIZE = 4096
+endif
 
 ifdef BOOTLOADER_SIZE
     OPT_DEFS += -DBOOTLOADER_SIZE=$(strip $(BOOTLOADER_SIZE))
diff --git a/docs/config_options.md b/docs/config_options.md
index eb0a441cc..33cb8da9b 100644
--- a/docs/config_options.md
+++ b/docs/config_options.md
@@ -289,6 +289,7 @@ This is a [make](https://www.gnu.org/software/make/manual/make.html) file that i
   * `halfkay`
   * `caterina`
   * `bootloadHID`
+  * `USBasp`
 
 ## Feature Options
 
diff --git a/docs/flashing.md b/docs/flashing.md
index 3b4582f00..833b9dd62 100644
--- a/docs/flashing.md
+++ b/docs/flashing.md
@@ -119,6 +119,31 @@ Flashing sequence:
 3. Flash a .hex file
 4. Reset the device into application mode (may be done automatically)
 
+## USBasploader
+
+USBasploader is a bootloader developed by matrixstorm. It is used in some non-USB AVR chips such as the ATmega328P, which run V-USB.
+
+To ensure compatibility with the USBasploader bootloader, make sure this block is present in your `rules.mk`:
+
+    # Bootloader
+    #     This definition is optional, and if your keyboard supports multiple bootloaders of
+    #     different sizes, comment this out, and the correct address will be loaded
+    #     automatically (+60). See bootloader.mk for all options.
+    BOOTLOADER = USBasp
+
+Compatible flashers:
+
+* [QMK Toolbox](https://github.com/qmk/qmk_toolbox/releases) (recommended GUI)
+* [avrdude](http://www.nongnu.org/avrdude/) with the `usbasp` programmer
+* [AVRDUDESS](https://github.com/zkemble/AVRDUDESS)
+
+Flashing sequence:
+
+1. Press the `RESET` keycode, or keep the boot pin shorted to GND while quickly shorting RST to GND
+2. Wait for the OS to detect the device
+3. Flash a .hex file
+4. Reset the device into application mode (may be done automatically)
+
 ## STM32
 
 All STM32 chips come preloaded with a factory bootloader that cannot be modified nor deleted. Some STM32 chips have bootloaders that do not come with USB programming (e.g. STM32F103) but the process is still the same.
diff --git a/keyboards/gingham/rules.mk b/keyboards/gingham/rules.mk
index b66b07129..83f424ba0 100644
--- a/keyboards/gingham/rules.mk
+++ b/keyboards/gingham/rules.mk
@@ -49,7 +49,7 @@ OPT_DEFS += -DINTERRUPT_CONTROL_ENDPOINT
 #   atmega32a    bootloadHID
 #
 # This uses usbaspbootloader
-# BOOTLOADER = atmel-dfu
+BOOTLOADER = USBasp
 
 # If you don't know the bootloader type, then you can specify the
 # Boot Section Size in *bytes* by uncommenting out the OPT_DEFS line
@@ -58,8 +58,6 @@ OPT_DEFS += -DINTERRUPT_CONTROL_ENDPOINT
 #   Atmel DFU loader    4096
 #   LUFA bootloader     4096
 #   USBaspLoader        2048
-# OPT_DEFS += -DBOOTLOADER_SIZE=4096
-OPT_DEFS += -DBOOTLOADER_SIZE=2048
 
 # Flash program via avrdude, but default command is not suitable.
 # You can use plaid:default:program
diff --git a/tmk_core/avr.mk b/tmk_core/avr.mk
index 6bf86d58a..670e141bf 100644
--- a/tmk_core/avr.mk
+++ b/tmk_core/avr.mk
@@ -245,6 +245,10 @@ avrdude-split-left: $(BUILD_DIR)/$(TARGET).hex check-size cpfirmware
 avrdude-split-right: $(BUILD_DIR)/$(TARGET).hex check-size cpfirmware
         $(call EXEC_AVRDUDE,eeprom-righthand.eep)
 
+usbasp: $(BUILD_DIR)/$(TARGET).hex check-size cpfirmware
+        avrdude -p $(MCU) -c usbasp -U flash:w:$(BUILD_DIR)/$(TARGET).hex
+
+
 # Convert hex to bin.
 bin: $(BUILD_DIR)/$(TARGET).hex
         $(OBJCOPY) -Iihex -Obinary $(BUILD_DIR)/$(TARGET).hex $(BUILD_DIR)/$(TARGET).bin
diff --git a/tmk_core/common/avr/bootloader.c b/tmk_core/common/avr/bootloader.c
index 3cdcd2e42..29036f7c5 100644
--- a/tmk_core/common/avr/bootloader.c
+++ b/tmk_core/common/avr/bootloader.c
@@ -65,6 +65,13 @@
 #define BOOT_SIZE_1024 0b010
 #define BOOT_SIZE_2048 0b000
 
+//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
@@ -149,6 +156,39 @@ void bootloader_jump(void) {
 
         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__)) // no USB - maybe BOOTLOADER_BOOTLOADHID instead though?
@@ -172,24 +212,19 @@ void bootloader_jump(void) {
 
 }
 
-#ifdef __AVR_ATmega32A__
-    // MCUSR is actually called MCUCSR in ATmega32A
-    #define MCUSR MCUCSR
-#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 ((MCUSR & (1<<WDRF)) && reset_key == BOOTLOADER_RESET_KEY) {
+        if ((MCUCSR & (1<<WDRF)) && reset_key == BOOTLOADER_RESET_KEY) {
             reset_key = 0;
 
             // My custom USBasploader requires this to come up.
-            MCUSR = 0;
+            MCUCSR = 0;
 
             // Seems like Teensy halfkay loader requires clearing WDRF and disabling watchdog.
-            MCUSR &= ~(1<<WDRF);
+            MCUCSR &= ~(1<<WDRF);
             wdt_disable();
 
 
@@ -202,29 +237,3 @@ void bootloader_jump_after_watchdog_reset(void)
         }
     #endif
 }
-
-
-#if 0
-    /*
-     * USBaspLoader - I'm not sure if this is used at all in any projects
-     *                would love to support it if it is -Jack
-     */
-#if defined(__AVR_ATmega168__) || defined(__AVR_ATmega168P__) || defined(__AVR_ATmega328P__)
-    // This makes custom USBasploader come up.
-    MCUSR = 0;
-
-    // initialize ports
-    PORTB = 0; PORTC= 0; PORTD = 0;
-    DDRB = 0; DDRC= 0; DDRD = 0;
-
-    // disable interrupts
-    EIMSK = 0; EECR = 0; SPCR = 0;
-    ACSR = 0; SPMCSR = 0; WDTCSR = 0; PCICR = 0;
-    TIMSK0 = 0; TIMSK1 = 0; TIMSK2 = 0;
-    ADCSRA = 0; TWCR = 0; UCSR0B = 0;
-#endif
-
-    // This is compled into 'icall', address should be in word unit, not byte.
-    ((void (*)(void))(BOOTLOADER_START/2))();
-}
-#endif