recipes/trs80: fix double line feeds

Lines should be terminated only with a CR on this system, not CRLF.

kernel/stdio.asm

@@ -76,6 +76,9 @@ printnstr:
 	pop	bc
 	ret
 
+; Prints a line terminator. This routine is a bit of a misnomer because it's
+; designed to be overridable to, for example, printlf, but we'll live with it
+; for now...
 printcrlf:
 	push	af
 	ld	a, CR

recipes/trs80/README.md

@@ -151,6 +151,10 @@ A memory range dumped this way will be re-loaded at the same offset through
 using the `RUN` command. Therefore, you can avoid all this work above in later
 sessions by simply typing `recv` in the DOS prompt.
 
+Note that you might want to turn `debug` off for these commands to run. I'm not
+sure why, but when the debugger is on, launching the command triggers the
+debugger.
+
 ## Sending binary through the RS-232 port
 
 Once you're finished punching your program in memory, you can run it with
@@ -186,6 +190,12 @@ If there was no error during `pingpong`, the content should be exact.
 Nevertheless, I recommend that you manually validate a few bytes using TRSDOS
 debugger before carrying on.
 
+*debugging tip*: Sometimes, the communication channel can be a bit stubborn and
+always fail, as if some leftover data was consistently blocking the channel. It
+would cause a data mismatch at the very beginning of the process, all the time.
+What I do in these cases is start a `COMM *cl` session on one side and a screen
+session on the other, type a few characters, and try `pingpong` again.
+
 ## Running Collapse OS
 
 If everything went well, you can run Collapse OS with `g3000<space>`. You'll

recipes/trs80/glue.asm

@@ -18,6 +18,9 @@
 .equ	STDIO_PUTC	trs80PutC
 .inc "stdio.asm"
 
+; The TRS-80 generates a double line feed if we give it both CR and LF.
+.equ	printcrlf	printcr
+
 ; *** BASIC ***
 
 ; RAM space used in different routines for short term processing.
@@ -44,4 +47,11 @@ init:
 	call	basInit
 	jp	basStart
 
+printcr:
+	push	af
+	ld	a, CR
+	call	STDIO_PUTC
+	pop	af
+	ret
+
 RAMSTART: