Supporting the TRS80 Model II

[stefano]

The list of the supported CP/M disk formats is now rather complete (CP/M Plus still missing), and I'm trying to enrich the library of this nice dinosaur.
I managed to page in the VRAM on the TRS80 model II, but ATM it works only with a single CP/M version, the P&T.

Trying to squeeze out some graphics, I'm now in one of those challenges

model2_graphics.png

..I guess an 80x72 pseudo-pixels rez is the most we can get

[stefano]

model2_text3.png

As said, at the moment it runs only on P&T CP/M.
It can be easily fixed to work also on low memory systems, but the memory banking on all the OS versions is an issue.

[stefano]

I managed to page the VRAM properly.
All the CP/M versions use bank 1, thus outputting $81 and $01 to port $FF seems to suffice.
In theory it might affect the timers but works

[RobertK]

When trying to compile like this...
zcc +cpm -subtype=ptcpm -lgfxtrs80m2 ......

...with the current nightly, it says:
error: file open: gfxtrs80m2.lib

That library seems to be missing.

[stefano]

I *think* it will be built tonight

[RobertK]

No success yet, there is only gfxtrs80.lib in the nightly package.

[dom]

Er, it's not been merged yet: https://github.com/z88dk/z88dk/pull/2299

[stefano]

ok.
Tomorrow morning, then !

[RobertK]

Thanks, now it's there and working!
Mono sprites perform very well in 80x72.

Another issue: can you get the virtual joysticks to work in CP/M?
They are supported on the TRS-80 Model 1 in native mode.

Compiling joytest.c for Model 2 CP/M results in these errors:

Code: Select all

joystick_inkey.asm:16: error: undefined symbol: keys_qaop
  ^---- keys_qaop
joystick_inkey.asm:19: error: undefined symbol: keys_8246
  ^---- keys_8246
joystick_inkey.asm:22: error: undefined symbol: keys_vi
  ^---- keys_vi
joystick_inkey.asm:25: error: undefined symbol: keys_cursor
  ^---- keys_cursor
joystick_sc.asm:37: error: undefined symbol: in_KeyPressed
  ^---- in_KeyPressed

[stefano]

There's a but of target specific I could add, eg timer. You might try the same library in trsdos mode , in the meanwhile

Edit: -subtype=cmd

[RobertK]

Oh, the .cmd file works with the model II as well, that makes life easier.

However, when running grtest from the .cmd file, there is no text output:

grtest_TRS80M2_CMDFile.jpg

When running it from Lifeboat CP/M, text output is there:

grtest_TRS80M2_CPM_Lifeboat.jpg

My compile commands look like this:

zcc +trs80 -lndos -lgfxtrs80m2 -create-app -o grtest_trs80_m2_LowRes.bin -subtype=cmd grtest.c -D__TRS80M2__
zcc +cpm -subtype=lifeboat -lgfxtrs80m2 -create-app -pragma-redirect:fputc_cons=fputc_cons_generic -o GT.COM grtest.c -D__TRS80M2__

[stefano]

Try avoiding the generic console support (not implemented yet). The native mode could work.

"-pragma-redirect:fputc_cons=fputc_cons_native"

[stefano]

I read the few documents I could find, it probably won't work.
MODEL II and 4 had different architectures and different ROM entries.
Possibly the model I could be emulated, but I'm avoiding to focus on a limited configuration just to work around the current issues.
I pulled in also the Model 4 160x72 mode (-lgfxtrs80m4), but any attempt to use any of the existing I/O console functions will either crash (in TRS80 mode, due to different ROM entries) or destroy the picture by entering in full text mode (CP/M mode).
The graphics library itself looks nice, though (you can run coswawe.c or other gfx output only stuff).

[stefano]

Considering the many different HW and SW architectures sharing the same brand name of TRS-80 I think we need to find the best compromise.
"fputc_cons_generic" in CP/M mode surprisingly runs fine on many CP/M versions of the TRS80 Model 4 and Model II but fails on P&T and FMG CP/M for the Model II and possibly others.
I'm wondering if and how to deal with direct hardware control for the console I/O on those 2 models. I put the target specific paging code (and base_graphics alteration) in swapgfxbk_m2.asm and swapgfxbk_m4.asm, but I probably need it also for stdio... Now I'm understanding why Dom decided to merge console and graphics, elsewhere !

By the way, since on Model 4 any call to BDOS restores the non-graphics font, I first need to learn how to decode the keyboard, first. Probably t's not happening soon.

[stefano]

Long story short: the fallback code to emulate the joystick is now in, for the nightly build.

[dom]

I'd recommend you do the same as I did with the Super80 - split into two different -clib options to handle the differences in ROM entry points. There's fundamental differences in the hardware and ROM to justify it and it just makes life easier.

[RobertK]

Long story short: the fallback code to emulate the joystick is now in, for the nightly build.

Thanks, Deepspace is now working in CP/M mode (albeit very blocky in 80x72, but surprisingly fast).

QAOP-NM and 8246-05 work fine, Cursor and hjkl-sd currently do not (no reaction).

Two more issues:
- Can you disable the blinking cursor?
- 1-Bit sound should be supported and available "out of the box" on the Model II (without any hardware expansion)? According to __HAVE_ONEBITSOUND it is not available, and my 1Bit.c test hangs when trying to play the first sound.

Attached are the WIP source files for testing.

[stefano]

I fixed the cursor issue when in graphics mode, I'm pulling the change today.

The sound is not present, actually the Model II does not have a tape interface.
I wrongly assumed the audio output trick evolved to a sort of standard because it was widely used, this is an abstract from the Service Manual for the model 4P:


5.1.13 Sound
The sound circuit in the Model4P is compatible with the Sound
Board which was optional in the Model 4. Sound is generated
by alternately selling and clearing data bif DO during an OUT to
port 90H. The stafe of DO is latched by U130 (1/2 of a 74LS74)
and the output is amplified by 02 which drives a piezoelectric
sound transducer. The speed of the software loop determines
the frequency, and thus, the pitch of the resulting tone. Since
the Model 4P does not have a cassette circuit, some existing
software that used the cassette output for sound would have
been lost. The Model 4P routes the cassette latch to the sound
board through U142. When the CASSMOTORON signal is a
logic low, the cassette motor is off, then the cassette output is
sent to the sound circuit.

[stefano]

I'm afraid I'm stuck.
Dom, how should I get the obj files built in the proper position for the mc6845 part ?

Code: Select all

(...)
zcc +trs80 -O2 -vn -c  -o obj/trs80m2/xorplot.o  xorplot.asm -Ca-I../.. -Ca-DFORtrs80m2
zcc +trs80 -O2 -vn -c  -o obj/trs80m2/xorplot_callee.o  xorplot_callee.asm -Ca-I../.. -Ca-DFORtrs80m2
TARGET=trs80m2 TYPE=z80 z88dk-z80asm -d -I/home/runner/work/z88dk/z88dk/lib/config//../ -DFORtrs80m2 -x/home/runner/work/z88dk/z88dk/libsrc//gfxtrs80m2 @/home/runner/work/z88dk/z88dk/libsrc//../libsrc//target/trs80/gfxtrs80m2.lst
video/mc6845/mc6845.lst:1: error: file not found: video/mc6845/obj/trs80m2/asm_set_cursor_state
  ^---- video/mc6845/obj/${TARGET}/asm_set_cursor_state
make: *** [Makefile:1752: gfxtrs80m2.lib] Error 1
make: Leaving directory '/home/runner/work/z88dk/z88dk/libsrc'
Error: Process completed with exit code 2.

https://github.com/z88dk/z88dk/pull/2348

[stefano]

Thank you Dominic

RobertK, the fixes should now be in.

[RobertK]

Is this a bug in the current low-res graphics logic (with the wrong character being used), or is this a compromise due to the limited character set?

TRS80_M2_HTron.png

[stefano]

If I remember correctly it is a compromise.

[RobertK]

Ok, no problem, this low-res graphics mode still looks very nice.

[stefano]

if you look at the picture at the beginning of this thread, I think I used characters 16, 18..1B and their inverse.

[RobertK]

Two issues with this target:

1. Virtual joystick support is broken once again, with my joytest.c program I'm getting the same compiler errors as posted above:

Code: Select all

joystick_inkey.asm:16: error: undefined symbol: keys_qaop
  ^---- keys_qaop
joystick_inkey.asm:19: error: undefined symbol: keys_8246
  ^---- keys_8246
joystick_inkey.asm:22: error: undefined symbol: keys_vi
  ^---- keys_vi
joystick_inkey.asm:25: error: undefined symbol: keys_cursor
  ^---- keys_cursor
joystick_sc.asm:37: error: undefined symbol: in_KeyPressed
  ^---- in_KeyPressed

I have checked the older releases that I have kept:

In the nightly build from 19 November 2023, it was still working.
In the nightly from 20 June 2024, it was no longer working.

So it got broken some time in between.


2. Can the blinking cursor be disabled somehow?