Interfacing with the 1520 printer plotter using DurexForth

[gdm413229]

I'm currently writing a 1520 interface library for DurexForth, and am currently struggling with the provided low-level device I/O routines. Any guidance is welcome and greatly appreciated.

[Whammo]

There are lots of examples for file handling I've left in discussions. Here is another.
You'll want to look at:
https://github.com/jkotlinski/durexforth/blob/master/forth_src/io.fs
and
https://github.com/jkotlinski/durexforth/blob/master/forth_src/open.fs

Device number is presumed to be DEVICE, so you only need file number and secondary address for OPEN.

6 DEVICE sets device number for plotter.

require io
: less \ less filename
parse-name ?dup if
else drop s" less"
then
8 8 open ioabort
clrchn
8 chkin ioabort
chrin chrin 2drop page  \ load address, clr screen
begin more chrin emit
readst until
clrchn 8 close
;

[Whammo]

Interesting- there doesn't seem to be a word for CHROUT in the io library.
This will be helpful and get you where you want to go.

: chrout ( b -- )
ar c! $ffd2 sys ;

[gdm413229]

Is the ar thing referencing the 6502/6510/8502's accumulator? That word might come in handy for doing low-level plotter functions through the KERNAL.

[Whammo]

We've hijacked the basic sys command and made available AR, XR, YR, and SR to preload for SYS, and they will be valid upon rts.

[Whammo]

Also, EMIT works the same as CHROUT even when output is redirected.
Similarly TYPE can be used for strings
TYPE ( caddr u -- )

[Whammo]

This is my best untested guess.

BASIC

open 1,6,0
print#1, "hello!"
CLOSE 1

FORTH

include io
: hello
6 device
0 0 1 0 open ioabort \ no filename, channel 1, sa 0
clrchn
s" hello!"
1 chkout ioabort type cr
clrchn
1 close ;

Edit: oops ioabort