gistfile1.txt

diff --git a/gbdk-lib/include/gb/gb.h b/gbdk-lib/include/gb/gb.h
index 3426c3a..7d51ce4 100644
--- a/gbdk-lib/include/gb/gb.h
+++ b/gbdk-lib/include/gb/gb.h
@@ -311,6 +311,7 @@ extern volatile UINT16 sys_time;
     @see set_interrupts() with @ref SIO_IFLAG
 */
 void send_byte(void);
+void send_byte_slave(void);
 
 /** Serial Link: Receive a byte from the serial port into @ref _io_in
 
diff --git a/gbdk-lib/libc/gb/serial.s b/gbdk-lib/libc/gb/serial.s
index 7e96374..19f0cc8 100644
--- a/gbdk-lib/libc/gb/serial.s
+++ b/gbdk-lib/libc/gb/serial.s
@@ -36,7 +36,7 @@
 
 	LDH	(.SC),A		; Use external clock
 	LD	A,#.DT_IDLE
-	LDH	(.SB),A		; Send IDLE byte
+	;LDH	(.SB),A		; Send IDLE byte
 	LD	A,#0x80
 	LDH	(.SC),A		; Use external clock
 
@@ -88,8 +88,8 @@ _remove_SIO::
 
 	XOR	A
 	LDH	(.SC),A		; Use external clock
-	LD	A,#.DT_IDLE
-	LDH	(.SB),A		; Reply with IDLE byte
+	;LD	A,#.DT_IDLE
+	;LDH	(.SB),A		; Reply with IDLE byte
 4$:
 	LD	A,#0x80
 	LDH	(.SC),A		; Enable transfer with external clock
@@ -135,6 +135,20 @@ _send_byte::			; Banked
 	LDH	(.SC),A		; Use internal clock
 	RET
 
+
+	;; Send byte in __io_out to the serial port
+.send_byte_slave:
+_send_byte_slave::			; Banked
+	LD	A,#.IO_SENDING
+	LD	(__io_status),A ; Store status
+	LD	A,#0x00
+	LDH	(.SC),A		; Use external clock
+	LD	A,(__io_out)
+	LDH	(.SB),A		; Send data byte
+	LD	A,#0x80
+	LDH	(.SC),A		; Use internal clock
+	RET
+
 	;; Receive byte from the serial port in __io_in
 .receive_byte:
 _receive_byte::			; Banked
@@ -142,8 +156,10 @@ _receive_byte::			; Banked
 	LD	(__io_status),A ; Store status
 	XOR	A
 	LDH	(.SC),A		; Use external clock
-	LD	A,#.DT_RECEIVING
-	LDH	(.SB),A		; Send RECEIVING byte
+	LD	A,(__io_out)
+	LDH	(.SB),A		; Send data byte
+	;LD	A,#.DT_RECEIVING
+	;LDH	(.SB),A		; Send RECEIVING byte
 	LD	A,#0x80
 	LDH	(.SC),A		; Use external clock
 	RET