Merge pull request #484 from jackhumbert/lets-split-support

Add Let's Split support

keyboards/atreus/Makefile

@@ -5,6 +5,7 @@ ifdef TEENSY2
     ATRUES_UPLOAD_COMMAND = teensy_loader_cli -w -mmcu=$(MCU) $(TARGET).hex
 else
     OPT_DEFS += -DATREUS_ASTAR
+    OPT_DEFS += -DCATERINA_BOOTLOADER
     ATRUES_UPLOAD_COMMAND = while [ ! -r $(USB) ]; do sleep 1; done; \
                             avrdude -p $(MCU) -c avr109 -U flash:w:$(TARGET).hex -P $(USB)
 endif

keyboards/lets_split/Makefile

@@ -0,0 +1,78 @@
+SRC += matrix.c \
+	   i2c.c \
+	   split_util.c \
+	   serial.c
+
+# MCU name
+#MCU = at90usb1287
+MCU = atmega32u4
+
+# Processor frequency.
+#     This will define a symbol, F_CPU, in all source code files equal to the
+#     processor frequency in Hz. You can then use this symbol in your source code to
+#     calculate timings. Do NOT tack on a 'UL' at the end, this will be done
+#     automatically to create a 32-bit value in your source code.
+#
+#     This will be an integer division of F_USB below, as it is sourced by
+#     F_USB after it has run through any CPU prescalers. Note that this value
+#     does not *change* the processor frequency - it should merely be updated to
+#     reflect the processor speed set externally so that the code can use accurate
+#     software delays.
+F_CPU = 16000000
+
+#
+# LUFA specific
+#
+# Target architecture (see library "Board Types" documentation).
+ARCH = AVR8
+
+# Input clock frequency.
+#     This will define a symbol, F_USB, in all source code files equal to the
+#     input clock frequency (before any prescaling is performed) in Hz. This value may
+#     differ from F_CPU if prescaling is used on the latter, and is required as the
+#     raw input clock is fed directly to the PLL sections of the AVR for high speed
+#     clock generation for the USB and other AVR subsections. Do NOT tack on a 'UL'
+#     at the end, this will be done automatically to create a 32-bit value in your
+#     source code.
+#
+#     If no clock division is performed on the input clock inside the AVR (via the
+#     CPU clock adjust registers or the clock division fuses), this will be equal to F_CPU.
+F_USB = $(F_CPU)
+
+# Interrupt driven control endpoint task(+60)
+OPT_DEFS += -DINTERRUPT_CONTROL_ENDPOINT
+
+
+# Boot Section Size in *bytes*
+#   Teensy halfKay   512
+#   Teensy++ halfKay 1024
+#   Atmel DFU loader 4096
+#   LUFA bootloader  4096
+#   USBaspLoader     2048
+OPT_DEFS += -DBOOTLOADER_SIZE=4096
+
+# Build Options
+#   change to "no" to disable the options, or define them in the Makefile in 
+#   the appropriate keymap folder that will get included automatically
+#
+BOOTMAGIC_ENABLE ?= no       # Virtual DIP switch configuration(+1000)
+MOUSEKEY_ENABLE ?= yes       # Mouse keys(+4700)
+EXTRAKEY_ENABLE ?= yes       # Audio control and System control(+450)
+CONSOLE_ENABLE ?= no         # Console for debug(+400)
+COMMAND_ENABLE ?= yes        # Commands for debug and configuration
+NKRO_ENABLE ?= no            # Nkey Rollover - if this doesn't work, see here: https://github.com/tmk/tmk_keyboard/wiki/FAQ#nkro-doesnt-work
+BACKLIGHT_ENABLE ?= no      # Enable keyboard backlight functionality
+MIDI_ENABLE ?= no            # MIDI controls
+AUDIO_ENABLE ?= yes           # Audio output on port C6
+UNICODE_ENABLE ?= no         # Unicode
+BLUETOOTH_ENABLE ?= no       # Enable Bluetooth with the Adafruit EZ-Key HID
+RGBLIGHT_ENABLE ?= no        # Enable WS2812 RGB underlight.  Do not enable this with audio at the same time.
+
+# 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

keyboards/lets_split/config.h

@@ -0,0 +1,98 @@
+/*
+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/>.
+*/
+
+#ifndef CONFIG_H
+#define CONFIG_H
+
+#include "config_common.h"
+
+/* USB Device descriptor parameter */
+#define VENDOR_ID       0xFEED
+#define PRODUCT_ID      0x3060
+#define DEVICE_VER      0x0001
+#define MANUFACTURER    Wootpatoot
+#define PRODUCT         Lets Split
+#define DESCRIPTION     A split keyboard for the cheap makers
+
+/* key matrix size */
+// Rows are doubled-up
+#define MATRIX_ROWS 8
+#define MATRIX_COLS 6
+
+// wiring of each half
+#define MATRIX_ROW_PINS { B5, B4, E6, D7 }
+#define MATRIX_COL_PINS { F4, F5, F6, F7, B1, B3 }
+
+#define CATERINA_BOOTLOADER
+
+// #define USE_I2C
+
+// #define EE_HANDS
+
+#define I2C_MASTER_LEFT
+// #define I2C_MASTER_RIGHT
+
+/* COL2ROW or ROW2COL */
+#define DIODE_DIRECTION COL2ROW
+
+/* define if matrix has ghost */
+//#define MATRIX_HAS_GHOST
+
+/* number of backlight levels */
+// #define BACKLIGHT_LEVELS 3
+
+/* Set 0 if debouncing isn't needed */
+#define DEBOUNCING_DELAY 5
+
+/* Mechanical locking support. Use KC_LCAP, KC_LNUM or KC_LSCR instead in keymap */
+#define LOCKING_SUPPORT_ENABLE
+/* Locking resynchronize hack */
+#define LOCKING_RESYNC_ENABLE
+
+/* key combination for command */
+#define IS_COMMAND() ( \
+    keyboard_report->mods == (MOD_BIT(KC_LSHIFT) | MOD_BIT(KC_RSHIFT)) \
+)
+
+/* ws2812 RGB LED */
+#define ws2812_PORTREG  PORTD
+#define ws2812_DDRREG   DDRD
+#define ws2812_pin PD1
+#define RGBLED_NUM 28     // Number of LEDs
+#define RGBLIGHT_HUE_STEP 10
+#define RGBLIGHT_SAT_STEP 17
+#define RGBLIGHT_VAL_STEP 17
+
+/*
+ * Feature disable options
+ *  These options are also useful to firmware size reduction.
+ */
+
+/* disable debug print */
+// #define NO_DEBUG
+
+/* disable print */
+// #define NO_PRINT
+
+/* disable action features */
+//#define NO_ACTION_LAYER
+//#define NO_ACTION_TAPPING
+//#define NO_ACTION_ONESHOT
+//#define NO_ACTION_MACRO
+//#define NO_ACTION_FUNCTION
+
+#endif

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);
+}

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

keyboards/lets_split/keymaps/default/keymap.c

@@ -0,0 +1,214 @@
+#include "lets_split.h"
+#include "action_layer.h"
+#include "eeconfig.h"
+
+extern keymap_config_t keymap_config;
+
+// Each layer gets a name for readability, which is then used in the keymap matrix below.
+// The underscores don't mean anything - you can have a layer called STUFF or any other name.
+// Layer names don't all need to be of the same length, obviously, and you can also skip them
+// entirely and just use numbers.
+#define _QWERTY 0
+#define _COLEMAK 1
+#define _DVORAK 2
+#define _LOWER 3
+#define _RAISE 4
+#define _ADJUST 16
+
+enum custom_keycodes {
+  QWERTY = SAFE_RANGE,
+  COLEMAK,
+  DVORAK,
+  LOWER,
+  RAISE,
+  ADJUST,
+};
+
+// Fillers to make layering more clear
+#define _______ KC_TRNS
+#define XXXXXXX KC_NO
+
+const uint16_t PROGMEM keymaps[][MATRIX_ROWS][MATRIX_COLS] = {
+
+/* Qwerty
+ * ,-----------------------------------------------------------------------------------.
+ * | Tab  |   Q  |   W  |   E  |   R  |   T  |   Y  |   U  |   I  |   O  |   P  | Bksp |
+ * |------+------+------+------+------+-------------+------+------+------+------+------|
+ * | Esc  |   A  |   S  |   D  |   F  |   G  |   H  |   J  |   K  |   L  |   ;  |  "   |
+ * |------+------+------+------+------+------|------+------+------+------+------+------|
+ * | Shift|   Z  |   X  |   C  |   V  |   B  |   N  |   M  |   ,  |   .  |   /  |Enter |
+ * |------+------+------+------+------+------+------+------+------+------+------+------|
+ * |Adjust| Ctrl | Alt  | GUI  |Lower |Space |Space |Raise | Left | Down |  Up  |Right |
+ * `-----------------------------------------------------------------------------------'
+ */
+[_QWERTY] = 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 , \
+  ADJUST,  KC_LCTL, KC_LALT, KC_LGUI, LOWER,   KC_SPC,  KC_SPC,  RAISE,   KC_LEFT, KC_DOWN, KC_UP,   KC_RGHT \
+),
+
+/* Colemak
+ * ,-----------------------------------------------------------------------------------.
+ * | Tab  |   Q  |   W  |   F  |   P  |   G  |   J  |   L  |   U  |   Y  |   ;  | Bksp |
+ * |------+------+------+------+------+-------------+------+------+------+------+------|
+ * | Esc  |   A  |   R  |   S  |   T  |   D  |   H  |   N  |   E  |   I  |   O  |  "   |
+ * |------+------+------+------+------+------|------+------+------+------+------+------|
+ * | Shift|   Z  |   X  |   C  |   V  |   B  |   K  |   M  |   ,  |   .  |   /  |Enter |
+ * |------+------+------+------+------+------+------+------+------+------+------+------|
+ * |Adjust| Ctrl | Alt  | GUI  |Lower |Space |Space |Raise | Left | Down |  Up  |Right |
+ * `-----------------------------------------------------------------------------------'
+ */
+[_COLEMAK] = KEYMAP( \
+  KC_TAB,  KC_Q,    KC_W,    KC_F,    KC_P,    KC_G,    KC_J,    KC_L,    KC_U,    KC_Y,    KC_SCLN, KC_BSPC, \
+  KC_ESC,  KC_A,    KC_R,    KC_S,    KC_T,    KC_D,    KC_H,    KC_N,    KC_E,    KC_I,    KC_O,    KC_QUOT, \
+  KC_LSFT, KC_Z,    KC_X,    KC_C,    KC_V,    KC_B,    KC_K,    KC_M,    KC_COMM, KC_DOT,  KC_SLSH, KC_ENT , \
+  ADJUST,  KC_LCTL, KC_LALT, KC_LGUI, LOWER,   KC_SPC,  KC_SPC,  RAISE,   KC_LEFT, KC_DOWN, KC_UP,   KC_RGHT \
+),
+
+/* Dvorak
+ * ,-----------------------------------------------------------------------------------.
+ * | Tab  |   "  |   ,  |   .  |   P  |   Y  |   F  |   G  |   C  |   R  |   L  | Bksp |
+ * |------+------+------+------+------+-------------+------+------+------+------+------|
+ * | Esc  |   A  |   O  |   E  |   U  |   I  |   D  |   H  |   T  |   N  |   S  |  /   |
+ * |------+------+------+------+------+------|------+------+------+------+------+------|
+ * | Shift|   ;  |   Q  |   J  |   K  |   X  |   B  |   M  |   W  |   V  |   Z  |Enter |
+ * |------+------+------+------+------+------+------+------+------+------+------+------|
+ * |Adjust| Ctrl | Alt  | GUI  |Lower |Space |Space |Raise | Left | Down |  Up  |Right |
+ * `-----------------------------------------------------------------------------------'
+ */
+[_DVORAK] = KEYMAP( \
+  KC_TAB,  KC_QUOT, KC_COMM, KC_DOT,  KC_P,    KC_Y,    KC_F,    KC_G,    KC_C,    KC_R,    KC_L,    KC_BSPC, \
+  KC_ESC,  KC_A,    KC_O,    KC_E,    KC_U,    KC_I,    KC_D,    KC_H,    KC_T,    KC_N,    KC_S,    KC_SLSH, \
+  KC_LSFT, KC_SCLN, KC_Q,    KC_J,    KC_K,    KC_X,    KC_B,    KC_M,    KC_W,    KC_V,    KC_Z,    KC_ENT , \
+  ADJUST,  KC_LCTL, KC_LALT, KC_LGUI, LOWER,   KC_SPC,  KC_SPC,  RAISE,   KC_LEFT, KC_DOWN, KC_UP,   KC_RGHT \
+),
+
+/* Lower
+ * ,-----------------------------------------------------------------------------------.
+ * |   ~  |   !  |   @  |   #  |   $  |   %  |   ^  |   &  |   *  |   (  |   )  | Bksp |
+ * |------+------+------+------+------+-------------+------+------+------+------+------|
+ * | Del  |  F1  |  F2  |  F3  |  F4  |  F5  |  F6  |   _  |   +  |     |    \  |  |   |
+ * |------+------+------+------+------+------|------+------+------+------+------+------|
+ * |      |  F7  |  F8  |  F9  |  F10 |  F11 |  F12 |ISO ~ |ISO | |      |      |Enter |
+ * |------+------+------+------+------+------+------+------+------+------+------+------|
+ * |      |      |      |      |      |             |      | Next | Vol- | Vol+ | Play |
+ * `-----------------------------------------------------------------------------------'
+ */
+[_LOWER] = KEYMAP( \
+  KC_TILD, KC_EXLM, KC_AT,   KC_HASH, KC_DLR,  KC_PERC, KC_CIRC, KC_AMPR, KC_ASTR, KC_LPRN, KC_RPRN, KC_BSPC, \
+  KC_DEL,  KC_F1,   KC_F2,   KC_F3,   KC_F4,   KC_F5,   KC_F6,   KC_UNDS, KC_PLUS, KC_LCBR, KC_RCBR, KC_PIPE, \
+  _______, KC_F7,   KC_F8,   KC_F9,   KC_F10,  KC_F11,  KC_F12,S(KC_NUHS),S(KC_NUBS),_______, _______, _______, \
+  _______, _______, _______, _______, _______, _______, _______, _______, KC_MNXT, KC_VOLD, KC_VOLU, KC_MPLY \
+),
+
+/* Raise
+ * ,-----------------------------------------------------------------------------------.
+ * |   `  |   1  |   2  |   3  |   4  |   5  |   6  |   7  |   8  |   9  |   0  | Bksp |
+ * |------+------+------+------+------+-------------+------+------+------+------+------|
+ * | Del  |  F1  |  F2  |  F3  |  F4  |  F5  |  F6  |   -  |   =  |   [  |   ]  |  \   |
+ * |------+------+------+------+------+------|------+------+------+------+------+------|
+ * |      |  F7  |  F8  |  F9  |  F10 |  F11 |  F12 |ISO # |ISO / |      |      |Enter |
+ * |------+------+------+------+------+------+------+------+------+------+------+------|
+ * |      |      |      |      |      |             |      | Next | Vol- | Vol+ | Play |
+ * `-----------------------------------------------------------------------------------'
+ */
+[_RAISE] = KEYMAP( \
+  KC_GRV,  KC_1,    KC_2,    KC_3,    KC_4,    KC_5,    KC_6,    KC_7,    KC_8,    KC_9,    KC_0,    KC_BSPC, \
+  KC_DEL,  KC_F1,   KC_F2,   KC_F3,   KC_F4,   KC_F5,   KC_F6,   KC_MINS, KC_EQL,  KC_LBRC, KC_RBRC, KC_BSLS, \
+  _______, KC_F7,   KC_F8,   KC_F9,   KC_F10,  KC_F11,  KC_F12,  KC_NUHS, KC_NUBS, _______, _______, _______, \
+  _______, _______, _______, _______, _______, _______, _______, _______, KC_MNXT, KC_VOLD, KC_VOLU, KC_MPLY \
+),
+
+/* Adjust (Lower + Raise)
+ * ,-----------------------------------------------------------------------------------.
+ * |      | Reset|      |      |      |      |      |      |      |      |      |  Del |
+ * |------+------+------+------+------+-------------+------+------+------+------+------|
+ * |      |      |      |Aud on|Audoff|AGnorm|AGswap|Qwerty|Colemk|Dvorak|      |      |
+ * |------+------+------+------+------+------|------+------+------+------+------+------|
+ * |      |      |      |      |      |      |      |      |      |      |      |      |
+ * |------+------+------+------+------+------+------+------+------+------+------+------|
+ * |      |      |      |      |      |             |      |      |      |      |      |
+ * `-----------------------------------------------------------------------------------'
+ */
+[_ADJUST] =  KEYMAP( \
+  _______, RESET,   _______, _______, _______, _______, _______, _______, _______, _______, _______, KC_DEL, \
+  _______, _______, _______, AU_ON,   AU_OFF,  AG_NORM, AG_SWAP, QWERTY,  COLEMAK, DVORAK,  _______, _______, \
+  _______, _______, _______, _______, _______, _______, _______, _______, _______, _______, _______, _______, \
+  _______, _______, _______, _______, _______, _______, _______, _______, _______, _______, _______, _______ \
+)
+
+
+};
+
+#ifdef AUDIO_ENABLE
+float tone_qwerty[][2]     = SONG(QWERTY_SOUND);
+float tone_dvorak[][2]     = SONG(DVORAK_SOUND);
+float tone_colemak[][2]    = SONG(COLEMAK_SOUND);
+#endif
+
+void persistant_default_layer_set(uint16_t default_layer) {
+  eeconfig_update_default_layer(default_layer);
+  default_layer_set(default_layer);
+}
+
+bool process_record_user(uint16_t keycode, keyrecord_t *record) {
+  switch (keycode) {
+    case QWERTY:
+      if (record->event.pressed) {
+        #ifdef AUDIO_ENABLE
+          PLAY_NOTE_ARRAY(tone_qwerty, false, 0);
+        #endif
+        persistant_default_layer_set(1UL<<_QWERTY);
+      }
+      return false;
+      break;
+    case COLEMAK:
+      if (record->event.pressed) {
+        #ifdef AUDIO_ENABLE
+          PLAY_NOTE_ARRAY(tone_colemak, false, 0);
+        #endif
+        persistant_default_layer_set(1UL<<_COLEMAK);
+      }
+      return false;
+      break;
+    case DVORAK:
+      if (record->event.pressed) {
+        #ifdef AUDIO_ENABLE
+          PLAY_NOTE_ARRAY(tone_dvorak, false, 0);
+        #endif
+        persistant_default_layer_set(1UL<<_DVORAK);
+      }
+      return false;
+      break;
+    case LOWER:
+      if (record->event.pressed) {
+        layer_on(_LOWER);
+        update_tri_layer(_LOWER, _RAISE, _ADJUST);
+      } else {
+        layer_off(_LOWER);
+        update_tri_layer(_LOWER, _RAISE, _ADJUST);
+      }
+      return false;
+      break;
+    case RAISE:
+      if (record->event.pressed) {
+        layer_on(_RAISE);
+        update_tri_layer(_LOWER, _RAISE, _ADJUST);
+      } else {
+        layer_off(_RAISE);
+        update_tri_layer(_LOWER, _RAISE, _ADJUST);
+      }
+      return false;
+      break;
+    case ADJUST:
+      if (record->event.pressed) {
+        layer_on(_ADJUST);
+      } else {
+        layer_off(_ADJUST);
+      }
+      return false;
+      break;
+  }
+  return true;
+}

keyboards/lets_split/lets_split.c

@@ -0,0 +1,30 @@
+#include "lets_split.h"
+
+#ifdef AUDIO_ENABLE
+    float tone_startup[][2] = SONG(STARTUP_SOUND);
+    float tone_goodbye[][2] = SONG(GOODBYE_SOUND);
+#endif
+
+void matrix_init_kb(void) {
+
+    #ifdef AUDIO_ENABLE
+        _delay_ms(20); // gets rid of tick
+        PLAY_NOTE_ARRAY(tone_startup, false, 0);
+    #endif
+
+    // // green led on
+    // DDRD |= (1<<5);
+    // PORTD &= ~(1<<5);
+
+    // // orange led on
+    // DDRB |= (1<<0);
+    // PORTB &= ~(1<<0);
+
+	matrix_init_user();
+};
+
+void shutdown_user(void) {
+    PLAY_NOTE_ARRAY(tone_goodbye, false, 0);
+    _delay_ms(150);
+    stop_all_notes();
+}

keyboards/lets_split/lets_split.h

@@ -0,0 +1,25 @@
+#ifndef LETS_SPLIT_H
+#define LETS_SPLIT_H
+
+#include "quantum.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 } \
+	}
+
+#endif

keyboards/lets_split/matrix.c

@@ -0,0 +1,311 @@
+/*
+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 "serial.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);
+}

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 */

keyboards/lets_split/readme.md

@@ -0,0 +1,102 @@
+Let's Split
+======
+
+This readme and most of the code are from https://github.com/ahtn/tmk_keyboard/
+
+Split keyboard firmware for Arduino Pro Micro or other ATmega32u4
+based boards.
+
+Features
+--------
+
+Some features supported by the firmware:
+
+* Either half can connect to the computer via USB, or both halves can be used
+  independently.
+* You only need 3 wires to connect the two halves. Two for VCC and GND and one
+  for serial communication.
+* Optional support for I2C connection between the two halves if for some
+  reason you require a faster connection between the two halves. Note this
+  requires an extra wire between halves and pull-up resistors on the data lines.
+
+Required Hardware
+-----------------
+
+Apart from diodes and key switches for the keyboard matrix in each half, you
+will need:
+
+* 2 Arduino Pro Micro's. You can find theses on aliexpress for ≈3.50USD each.
+* 2 TRS sockets
+* 1 TRS cable.
+
+Alternatively, you can use any sort of cable and socket that has at least 3
+wires. If you want to use I2C to communicate between halves, you will need a
+cable with at least 4 wires and 2x 4.7kΩ pull-up resistors
+
+Optional Hardware
+-----------------
+
+A speaker can be hooked-up to either side to the `5` (`C6`) pin and `GND`, and turned on via `AUDIO_ENABLE`.
+
+Wiring
+------
+
+The 3 wires of the TRS cable need to connect GND, VCC, and digital pin 3 (i.e.
+PD0 on the ATmega32u4) between the two Pro Micros.
+
+Then wire your key matrix to any of the remaining 17 IO pins of the pro micro
+and modify the `matrix.c` accordingly.
+
+The wiring for serial:
+
+![serial wiring](imgs/split-keyboard-serial-schematic.png)
+
+The wiring for i2c:
+
+![i2c wiring](imgs/split-keyboard-i2c-schematic.png)
+
+The pull-up resistors may be placed on either half. It is also possible
+to use 4 resistors and have the pull-ups in both halves, but this is
+unnecessary in simple use cases.
+
+Notes on Software Configuration
+-------------------------------
+
+Configuring the firmware is similar to any other TMK project. One thing
+to note is that `MATIX_ROWS` in `config.h` is the total number of rows between
+the two halves, i.e. if your split keyboard has 4 rows in each half, then
+`MATRIX_ROWS=8`.
+
+Also the current implementation assumes a maximum of 8 columns, but it would
+not be very difficult to adapt it to support more if required.
+
+
+Flashing
+--------
+
+If you define `EE_HANDS` in your `config.h`, you will need to set the
+EEPROM for the left and right halves. The EEPROM is used to store whether the
+half is left handed or right handed. This makes it so that the same firmware
+file will run on both hands instead of having to flash left and right handed
+versions of the firmware to each half. To flash the EEPROM file for the left
+half run:
+```
+make eeprom-left
+```
+and similarly for right half
+```
+make eeprom-right
+```
+
+After you have flashed the EEPROM for the first time, you then need to program
+the flash memory:
+```
+make program
+```
+Note that you need to program both halves, but you have the option of using
+different keymaps for each half. You could program the left half with a QWERTY
+layout and the right half with a Colemak layout. Then if you connect the left
+half to a computer by USB the keyboard will use QWERTY and Colemak when the
+right half is connected.
+
+

keyboards/lets_split/serial.c

@@ -0,0 +1,225 @@
+/*
+ * WARNING: be careful changing this code, it is very timing dependent
+ */
+
+#ifndef F_CPU
+#define F_CPU 16000000
+#endif
+
+#include <avr/io.h>
+#include <avr/interrupt.h>
+#include <util/delay.h>
+#include <stdbool.h>
+
+#include "serial.h"
+
+// Serial pulse period in microseconds. Its probably a bad idea to lower this
+// value.
+#define SERIAL_DELAY 24
+
+uint8_t volatile serial_slave_buffer[SERIAL_SLAVE_BUFFER_LENGTH] = {0};
+uint8_t volatile serial_master_buffer[SERIAL_MASTER_BUFFER_LENGTH] = {0};
+
+#define SLAVE_DATA_CORRUPT (1<<0)
+volatile uint8_t status = 0;
+
+inline static
+void serial_delay(void) {
+  _delay_us(SERIAL_DELAY);
+}
+
+inline static
+void serial_output(void) {
+  SERIAL_PIN_DDR |= SERIAL_PIN_MASK;
+}
+
+// make the serial pin an input with pull-up resistor
+inline static
+void serial_input(void) {
+  SERIAL_PIN_DDR  &= ~SERIAL_PIN_MASK;
+  SERIAL_PIN_PORT |= SERIAL_PIN_MASK;
+}
+
+inline static
+uint8_t serial_read_pin(void) {
+  return !!(SERIAL_PIN_INPUT & SERIAL_PIN_MASK);
+}
+
+inline static
+void serial_low(void) {
+  SERIAL_PIN_PORT &= ~SERIAL_PIN_MASK;
+}
+
+inline static
+void serial_high(void) {
+  SERIAL_PIN_PORT |= SERIAL_PIN_MASK;
+}
+
+void serial_master_init(void) {
+  serial_output();
+  serial_high();
+}
+
+void serial_slave_init(void) {
+  serial_input();
+
+  // Enable INT0
+  EIMSK |= _BV(INT0);
+  // Trigger on falling edge of INT0
+  EICRA &= ~(_BV(ISC00) | _BV(ISC01));
+}
+
+// Used by the master to synchronize timing with the slave.
+static
+void sync_recv(void) {
+  serial_input();
+  // This shouldn't hang if the slave disconnects because the
+  // serial line will float to high if the slave does disconnect.
+  while (!serial_read_pin());
+  serial_delay();
+}
+
+// Used by the slave to send a synchronization signal to the master.
+static
+void sync_send(void) {
+  serial_output();
+
+  serial_low();
+  serial_delay();
+
+  serial_high();
+}
+
+// Reads a byte from the serial line
+static
+uint8_t serial_read_byte(void) {
+  uint8_t byte = 0;
+  serial_input();
+  for ( uint8_t i = 0; i < 8; ++i) {
+    byte = (byte << 1) | serial_read_pin();
+    serial_delay();
+    _delay_us(1);
+  }
+
+  return byte;
+}
+
+// Sends a byte with MSB ordering
+static
+void serial_write_byte(uint8_t data) {
+  uint8_t b = 8;
+  serial_output();
+  while( b-- ) {
+    if(data & (1 << b)) {
+      serial_high();
+    } else {
+      serial_low();
+    }
+    serial_delay();
+  }
+}
+
+// interrupt handle to be used by the slave device
+ISR(SERIAL_PIN_INTERRUPT) {
+  sync_send();
+
+  uint8_t checksum = 0;
+  for (int i = 0; i < SERIAL_SLAVE_BUFFER_LENGTH; ++i) {
+    serial_write_byte(serial_slave_buffer[i]);
+    sync_send();
+    checksum += serial_slave_buffer[i];
+  }
+  serial_write_byte(checksum);
+  sync_send();
+
+  // wait for the sync to finish sending
+  serial_delay();
+
+  // read the middle of pulses
+  _delay_us(SERIAL_DELAY/2);
+
+  uint8_t checksum_computed = 0;
+  for (int i = 0; i < SERIAL_MASTER_BUFFER_LENGTH; ++i) {
+    serial_master_buffer[i] = serial_read_byte();
+    sync_send();
+    checksum_computed += serial_master_buffer[i];
+  }
+  uint8_t checksum_received = serial_read_byte();
+  sync_send();
+
+  serial_input(); // end transaction
+
+  if ( checksum_computed != checksum_received ) {
+    status |= SLAVE_DATA_CORRUPT;
+  } else {
+    status &= ~SLAVE_DATA_CORRUPT;
+  }
+}
+
+inline
+bool serial_slave_DATA_CORRUPT(void) {
+  return status & SLAVE_DATA_CORRUPT;
+}
+
+// Copies the serial_slave_buffer to the master and sends the
+// serial_master_buffer to the slave.
+//
+// Returns:
+// 0 => no error
+// 1 => slave did not respond
+int serial_update_buffers(void) {
+  // this code is very time dependent, so we need to disable interrupts
+  cli();
+
+  // signal to the slave that we want to start a transaction
+  serial_output();
+  serial_low();
+  _delay_us(1);
+
+  // wait for the slaves response
+  serial_input();
+  serial_high();
+  _delay_us(SERIAL_DELAY);
+
+  // check if the slave is present
+  if (serial_read_pin()) {
+    // slave failed to pull the line low, assume not present
+    sei();
+    return 1;
+  }
+
+  // if the slave is present syncronize with it
+  sync_recv();
+
+  uint8_t checksum_computed = 0;
+  // receive data from the slave
+  for (int i = 0; i < SERIAL_SLAVE_BUFFER_LENGTH; ++i) {
+    serial_slave_buffer[i] = serial_read_byte();
+    sync_recv();
+    checksum_computed += serial_slave_buffer[i];
+  }
+  uint8_t checksum_received = serial_read_byte();
+  sync_recv();
+
+  if (checksum_computed != checksum_received) {
+    sei();
+    return 1;
+  }
+
+  uint8_t checksum = 0;
+  // send data to the slave
+  for (int i = 0; i < SERIAL_MASTER_BUFFER_LENGTH; ++i) {
+    serial_write_byte(serial_master_buffer[i]);
+    sync_recv();
+    checksum += serial_master_buffer[i];
+  }
+  serial_write_byte(checksum);
+  sync_recv();
+
+  // always, release the line when not in use
+  serial_output();
+  serial_high();
+
+  sei();
+  return 0;
+}

keyboards/lets_split/serial.h

@@ -0,0 +1,26 @@
+#ifndef MY_SERIAL_H
+#define MY_SERIAL_H
+
+#include "config.h"
+#include <stdbool.h>
+
+/* TODO:  some defines for interrupt setup */
+#define SERIAL_PIN_DDR DDRD
+#define SERIAL_PIN_PORT PORTD
+#define SERIAL_PIN_INPUT PIND
+#define SERIAL_PIN_MASK _BV(PD0)
+#define SERIAL_PIN_INTERRUPT INT0_vect
+
+#define SERIAL_SLAVE_BUFFER_LENGTH MATRIX_ROWS/2
+#define SERIAL_MASTER_BUFFER_LENGTH 1
+
+// Buffers for master - slave communication
+extern volatile uint8_t serial_slave_buffer[SERIAL_SLAVE_BUFFER_LENGTH];
+extern volatile uint8_t serial_master_buffer[SERIAL_MASTER_BUFFER_LENGTH];
+
+void serial_master_init(void);
+void serial_slave_init(void);
+int serial_update_buffers(void);
+bool serial_slave_data_corrupt(void);
+
+#endif

keyboards/lets_split/split_util.c

@@ -0,0 +1,76 @@
+#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 "serial.h"
+#include "keyboard.h"
+#include "config.h"
+
+volatile bool isLeftHand = true;
+
+static void setup_handedness(void) {
+  #ifdef EE_HANDS
+    isLeftHand = eeprom_read_byte(EECONFIG_HANDEDNESS);
+  #else
+    #ifdef I2C_MASTER_RIGHT
+      isLeftHand = !has_usb();
+    #else
+      isLeftHand = has_usb();
+    #endif
+  #endif
+}
+
+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();
+    }
+}

keyboards/lets_split/split_util.h

@@ -0,0 +1,22 @@
+#ifndef SPLIT_KEYBOARD_UTIL_H
+#define SPLIT_KEYBOARD_UTIL_H
+
+#include <stdbool.h>
+
+#ifdef EE_HANDS
+	#define EECONFIG_BOOTMAGIC_END      (uint8_t *)10
+	#define EECONFIG_HANDEDNESS         EECONFIG_BOOTMAGIC_END
+#endif
+
+#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

quantum/quantum.c

@@ -89,7 +89,7 @@ bool process_record_quantum(keyrecord_t *record) {
           shutdown_user();
         #endif
         wait_ms(250);
-        #ifdef ATREUS_ASTAR
+        #ifdef CATERINA_BOOTLOADER
             *(uint16_t *)0x0800 = 0x7777; // these two are a-star-specific
         #endif
         bootloader_jump();

tmk_core/common/avr/bootloader.c

@@ -73,6 +73,8 @@ uint32_t reset_key  __attribute__ ((section (".noinit")));
 
 /* initialize MCU status by watchdog reset */
 void bootloader_jump(void) {
+    #ifndef CATERINA_BOOTLOADER
+
         #ifdef PROTOCOL_LUFA
             USB_Disable();
             cli();
@@ -91,8 +93,26 @@ void bootloader_jump(void) {
         reset_key = BOOTLOADER_RESET_KEY;
         wdt_enable(WDTO_250MS);
         for (;;);
-}
 
+    #else
+        // 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
+
+    #endif
+}
 
 /* this runs before main() */
 void bootloader_jump_after_watchdog_reset(void) __attribute__ ((used, naked, section (".init3")));

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