WIP reimplementing serial terminal with DATA_AVAILABLE register

assembly/bios/drivers/arduino_terminal.asm

@@ -3,6 +3,7 @@
 
 ; config (IO port 0)
 TERM_DATA_REG: EQU IO_0
+TERM_DATA_AVAIL_REG: EQU IO_0 + 1
 
 ; variables
 TERM_VAR_SPACE: EQU DRV_VAR_SPACE + 128
@@ -26,7 +27,9 @@ Term_printc:
     out (TERM_DATA_REG),a
     ret
 
-; Reads a single character. 0s are ignored (can be used with keyboard)
+; Reads a single character. 0s are ignored (can be used with keyboard).
+; Doesn't check DATA_AVAILABLE register of parallel port, because a 0 byte
+; is ignored anyway (it represents the ASCII NUL control char).
 ; @return A The read character
 Term_readc:
     in a, (TERM_DATA_REG)    ; reads a character
@@ -35,6 +38,8 @@ Term_readc:
     ret ; if not NULL, returns it in the a register
 
 ; Reads a line. 0s are ignored (can be used with keyboard)
+; Doesn't check DATA_AVAILABLE register of parallel port, because a 0 byte
+; is ignored anyway (it represents the ASCII NUL control char).
 ; @return BC The pointer to a null-terminated read string
 Term_readline:
     ld bc, incoming_string  ; this array will contain read string
@@ -56,9 +61,17 @@ Term_readline:
     ld bc, incoming_string  ; Returns read string pointer
     ret
 
-; Reads the byte currently on the I/O bus at the provided address.
+; Returns the number of bytes available on the parallel port using the 
+; DATA_AVAILABLE register.
+; @return a the number of available bytes
+Term_availb:
+    in a, (TERM_DATA_AVAIL_REG)
+    ret
+
+; Reads the first available byte on the serial port using the DATA register.
 ; 0s are not ignored (cannot be used with keyboard)
 ; Affects NO condition bits!
+; @return the available byte, even if 0
 Term_readb:
     in a, (TERM_DATA_REG)    ; reads a byte
     ret

assembly/bios/monitor.asm

@@ -25,6 +25,7 @@ MON_ARG_HEX: DB "    0x",0
 MON_HELP: DB 10,"Available commands:\nHELP prints this message\nDUMP shows memory content\nSET sets memory content LOAD\nRUN executes code\nADB starts Assembly Deploy Bridge",0
 MON_MSG_ADB: DB 10,"Waiting for data.",0
 MON_ERR_SYNTAX: DB "    Syntax error",0
+;MON_ADB_TIMEOUT: EQU 0xFF     // Number of cycles after an ADB binary transfer is considered completed
 
 Monitor_main:
     ; Print welcome string
@@ -101,8 +102,10 @@ monitor_adb:
     call Print
     ; start copying incoming data to application space
     call monitor_copyTermToAppMem
-    jp APP_SPACE    ; Start executing code
-    ;jp monitor_main_loop
+    ;jp APP_SPACE    ; Start executing code
+    ld bc, APP_SPACE
+    call Print
+    jp monitor_main_loop
 
 ; Read 1 hex byte (e.g. 0x8C)
 monitor_arg_byte:
@@ -160,22 +163,21 @@ monitor_readHexDigit:
     ret
 
 ; Copy data from STDIN to application memory. This is tought to be used with parallel terminal, not keyboard:
-; 0s are not ignored and the sequence is complete when found 8 zeros.
+; 0s are not ignored and the sequence is complete when no data is available for 8 cpu cycles.
 monitor_copyTermToAppMem:
-    call Term_readb
-    cp 0
-    jp z, monitor_copyTermToAppMem     ; wait for data stream to begin: ignore leading zeros
     ld hl, APP_SPACE    ; we will write in APP_SPACE
-    ld b, 8     ; the number of zeros that represent the end of stream
+    ld b, 255; MON_ADB_TIMEOUT     ; the timeout counter (number cycles without available data that represent the end of stream)
     monitor_copyTermToAppMem_loop:
+    dec b   ; decrement the timeout counter
+    ret 0   ; if counter is 0, timeout reached: return
+    ; check if bytes are available
+    call Term_availb
+    cp 0
+    jp z, monitor_copyTermToAppMem     ; no bytes available, next loop
+    ; bytes are available
+    ld b, 255 ;MON_ADB_TIMEOUT; reset the counter
     ld (hl), a  ; copy byte to memory
     inc hl  ; move to next memory position
-    cp 0    ; compare A to 0
-    ; load next byte to A (this doesn't affect condition bits, so flag Z from previous cp is still valid)
-    call Term_readb
-    jp nz, monitor_copyTermToAppMem_loop   ; if during previous cp A was not 0, execute next cycle
-    dec b   ; if A is 0, decrement "end of stream" counter
-    ret z   ; if B is 0, we found 8 zeros, so the stream is finished: return.
-    jp monitor_copyTermToAppMem_loop   ; otherwise, continue loop
+    jp monitor_copyTermToAppMem_loop   ; continue loop