4 files changed, 77 insertions, 13 deletions
diff --git a/quantum/split_common/serial.c b/quantum/split_common/serial.c
index 74bcbb6bf6..f34f824d7d 100644
--- a/quantum/split_common/serial.c
+++ b/quantum/split_common/serial.c
@@ -14,6 +14,59 @@
 
 #ifndef USE_I2C
 
+#ifndef SOFT_SERIAL_PIN
+  #error quantum/split_common/serial.c need SOFT_SERIAL_PIN define
+#endif
+
+#ifdef __AVR_ATmega32U4__
+  // if using ATmega32U4 I2C, can not use PD0 and PD1 in soft serial.
+  #ifdef USE_I2C
+    #if SOFT_SERIAL_PIN == D0 || SOFT_SERIAL_PIN == D1
+      #error Using ATmega32U4 I2C, so can not use PD0, PD1
+    #endif
+  #endif
+
+  #if SOFT_SERIAL_PIN >= D0 && SOFT_SERIAL_PIN <= D3
+    #define SERIAL_PIN_DDR   DDRD
+    #define SERIAL_PIN_PORT  PORTD
+    #define SERIAL_PIN_INPUT PIND
+    #if SOFT_SERIAL_PIN == D0
+      #define SERIAL_PIN_MASK _BV(PD0)
+      #define EIMSK_BIT       _BV(INT0)
+      #define EICRx_BIT       (~(_BV(ISC00) | _BV(ISC01)))
+      #define SERIAL_PIN_INTERRUPT INT0_vect
+    #elif  SOFT_SERIAL_PIN == D1
+      #define SERIAL_PIN_MASK _BV(PD1)
+      #define EIMSK_BIT       _BV(INT1)
+      #define EICRx_BIT       (~(_BV(ISC10) | _BV(ISC11)))
+      #define SERIAL_PIN_INTERRUPT INT1_vect
+    #elif  SOFT_SERIAL_PIN == D2
+      #define SERIAL_PIN_MASK _BV(PD2)
+      #define EIMSK_BIT       _BV(INT2)
+      #define EICRx_BIT       (~(_BV(ISC20) | _BV(ISC21)))
+      #define SERIAL_PIN_INTERRUPT INT2_vect
+    #elif  SOFT_SERIAL_PIN == D3
+      #define SERIAL_PIN_MASK _BV(PD3)
+      #define EIMSK_BIT       _BV(INT3)
+      #define EICRx_BIT       (~(_BV(ISC30) | _BV(ISC31)))
+      #define SERIAL_PIN_INTERRUPT INT3_vect
+    #endif
+  #elif  SOFT_SERIAL_PIN == E6
+    #define SERIAL_PIN_DDR   DDRE
+    #define SERIAL_PIN_PORT  PORTE
+    #define SERIAL_PIN_INPUT PINE
+    #define SERIAL_PIN_MASK  _BV(PE6)
+    #define EIMSK_BIT        _BV(INT6)
+    #define EICRx_BIT        (~(_BV(ISC60) | _BV(ISC61)))
+    #define SERIAL_PIN_INTERRUPT INT6_vect
+  #else
+  #error invalid SOFT_SERIAL_PIN value
+  #endif
+
+#else
+ #error serial.c now support ATmega32U4 only
+#endif
+
 // Serial pulse period in microseconds. Its probably a bad idea to lower this
 // value.
 #define SERIAL_DELAY 24
diff --git a/quantum/split_common/serial.h b/quantum/split_common/serial.h
index e566eb8a06..0b99f352d0 100644
--- a/quantum/split_common/serial.h
+++ b/quantum/split_common/serial.h
@@ -1,21 +1,18 @@
 #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
-
-// Address location defines 
-#define SERIAL_BACKLIT_START   0x00
+// /////////////////////////////////////////////////////////////////
+// Need Soft Serial defines in config.h
+// /////////////////////////////////////////////////////////////////
+// ex.
+//  /* Configuration of lower interface with the lower layer(hardware) of serial.c */
+//  #define SOFT_SERIAL_PIN ??   // ?? = D0,D1,D2,D3,E6
+//
+//  /* Configuration of upper interface with the upper layer of serial.c */
+//  #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];
diff --git a/quantum/split_common/serial_backward_compatibility.h b/quantum/split_common/serial_backward_compatibility.h
new file mode 100644
index 0000000000..216b6c41ff
--- /dev/null
+++ b/quantum/split_common/serial_backward_compatibility.h
@@ -0,0 +1,11 @@
+/* serial.h backward compatibility */
+
+// #ifndef SOFT_SERIAL_PIN
+//  #define SOFT_SERIAL_PIN D0
+// #endif
+
+#ifndef SERIAL_SLAVE_BUFFER_LENGTH
+ #define SERIAL_SLAVE_BUFFER_LENGTH MATRIX_ROWS/2
+ #define SERIAL_MASTER_BUFFER_LENGTH 1
+#endif
+
diff --git a/quantum/split_common/split_util.h b/quantum/split_common/split_util.h
index d6cf3e72a9..45e8db0f2f 100644
--- a/quantum/split_common/split_util.h
+++ b/quantum/split_common/split_util.h
@@ -7,6 +7,9 @@
 #include <stdlib.h>
 #include "eeconfig.h"
 
+// backlight level store index in serial_master_buffer[] for slave to read
+#define SERIAL_BACKLIT_START   0x00
+
 #define SLAVE_I2C_ADDRESS           0x32
 
 extern volatile bool isLeftHand;