Fix for 0x00 byte

Makefile

@@ -1,5 +1,9 @@
-.PHONY: all
+.PHONY: all clean
 
 all:
 	make -C driver
 	make -C example disk
+
+clean:
+	make clean -C driver
+	make clean -C example

README.md

@@ -5,5 +5,8 @@ This is an implementation of a reliable 2400b serial driver for the userport of
 Based on George Hug's 'Towards 2400' article in the Transactor Magazine volume 9 issue 3.
 (https://archive.org/details/transactor-magazines-v9-i03)
 
+I used this fix to get around the 0x0d problem when a 0 byte is received.
+(https://modelrail.otenko.com/electronics/commodore-64-fixing-rs-232-serial-limitations)
+
 Cheers,
 Johan

driver/c64-up2400.s

@@ -147,7 +147,7 @@ GET:
         jsr CHKIN
         jsr rshavedata
         beq GET_NO_DATA
-        jsr BASIN
+        jsr OURBASIN
         ldx #$00
         sta (ptr1,x)
         jsr CLRCH 
@@ -160,6 +160,19 @@ GET_NO_DATA:
         ldx #>SER_ERR_NO_DATA 
         rts
 
+;----------------------------------------------------------------------------
+; OURBASIN: This is a minimised call to get the character from the buffer.
+; The Kernal code does not allow zero bytes (0x00)... this does.
+;
+
+OURBASIN:
+        jsr $F14E
+        bcc @exit
+        jmp $F1B4
+@exit
+        clc
+        rts
+
 ;----------------------------------------------------------------------------
 ; PUT: Output character in A.
 ; Must return an error code in a/x.
@@ -185,6 +198,7 @@ STATUS:
         lda     #<SER_ERR_OK
         tax
         rts
+
 ;----------------------------------------------------------------------------
 ; IOCTL: Driver defined entry point. The wrapper will pass a pointer to ioctl
 ; specific data in ptr1, and the ioctl code in A.