Re: [hatari-devel] Proposal: use Atari keyboard with Hatari

[Vincent Barrilliot <vincent.barrilliot@xxxxxxxxxxx>]

Hello,


I have a proof of concept for this now. I can use the ATARI's keyboard 
and mouse in Hatari :) I think this can help for people who want to 
build a "fake" Atari using an old  Atari keyboard and a raspberry pie!

I recorded a small demo video (81 seconds) which you can watch here

https://youtu.be/r-ojz6_FO3E


Here's what I did:

* create a module external_ikbd.c which opens the serial port (9600bps) 
and runs 2 threads, one for getting data from the serial and put in an 
"inbound" circular buffer, the other thread for sending data from an 
"outbound" circular buffer to the serial port.

* adapt main.c so it calls the initialization code of that module

* adapt acia.c so to

  * check the "inbound" buffer and fake reception of that byte into the 
keyboard ACIA

  * write the data that the ACIA would sent to "outbound" circular buffer


It has the following limitations:

* I haven't disabled the PC's keyboard and mouse handling. So you can 
use both the PC and the Atari keyboard mouse. But if you use both at the 
same time, multiple-byte IKBD packets will get corrupt and can lead to 
unexpected effects in the TOS.

* I added a config switch but it's hardcoded, there is no UI to 
configure it.

* The serial port handling is linux-specific.

* There is no error handling of what happens on the serial port.


I have some questions:

1 What's your view on this change ? Any chance you would ever accept to 
merge that in hatari ? I think using keyboard/mouse is ok because you 
can hardly loose data in case something goes wrong. It's not like using 
a DMA device through a serial line with all the trouble that Nicolas 
mentioned.

2 I would like to add configuration. I found that there is a good 
looking pythonui in addition to the SDL one. Why is that ? Is one of 
them going to be retired / would I need to support both ?

3 It works on linux only. I think I can make it work with anything that 
support struct termios (like the RS-232 emulation does). Should I 
refactor to make this RS232 more reusable (it currently uses some static 
variables) or it's better to keep the external ikbd stuff a completely a 
separate implementation ?


Kind regards


Vinz


On 30/12/2020 15:12, Vincent Barrilliot wrote:
> Hi,
>
>
> Thank you Laurent for the insight. Indeed I did not consider these 
> situations !
>
> But I think the situation is different (I mean simpler) than with a 
> floppy because there is no hard coupling between the keyboard and the 
> computer (e.g. no DMA involved, they use "different" clocks etc.). In 
> the worst case we can have overruns if hatari runs too slow, but that 
> could happen as well on real hardware if ACIA interrupts are masked 
> and I guess/hope that TOS handles it.
>
> I think baud speed is not a big problem, we just need to inject the 
> received byte from the remote IKBD into the ACIA's data register, 
> rather than build it up using the bit-shift register. Same for sending 
> Atari->IKBD.
>
> I'll look at the MIDI implementation because it must be doing 
> something similar.
>
> Anyway, I'll try it for fun I'll how far I get:)
>
> Kind regards
>
>
> Vincent
>
>
> Le 29/12/2020 à 17:32, Nicolas Pomarède a écrit :
> > Le 28/12/2020 à 15:41, Vincent Barrilliot a écrit :
> > > Dear Hatari developers,
> > >
> > >
> > > I have an STf which I don't use much. I'd like to add an option to 
> > > Hatari so that instead of emulating the IKBD we would simply use 
> > > that of a real ST through serial ports, so to get the feeling of 
> > > using a real ST but with all advantages of Hatari.
> > >
> > > For this want to I connect the ST to the PC using serial port, then 
> > > I run a program on the Hatari that hooks into $118 and transfers all 
> > > the IKBD's traffic to the PC's serial port (I've left MIDI out of 
> > > the picture for now, as the 19200 line wouldn't keep up with the 
> > > MIDI's 31250bps). Of course the ST becomes unusable from that point 
> > > because the TOS doesn't get any IKBD or MIDI event anymore.
> > >
> > > Then I need to update Hatari, the configuration GUI etc.
> > >
> > >
> > >   I would like to know:
> > >
> > > * what you think about this idea
> > >
> > > * (so that if I ever submit a patch achieving that you'll agree to 
> > > merge it in)
> > >
> > > * if you have any advice to give me for doing that, pitfalls, things 
> > > to be cautious about etc.
> > >
> > > I think I know the ikbd.c well now. I still have my patch to submit 
> > > to improve keyboard support, in particular for characters requiring 
> > > key combinations on either the PC and/or the Atari but there are 
> > > other things in progress so I'm waiting for a better moment to bring 
> > > that subject again.
> > >
> > > Kind regards
> > >
> > >
> > > Vinz
> >
> > Hi
> >
> > I think there will be similar issue when doing this than when trying 
> > to access a real floppy drive from Hatari (which was requested by 
> > some users)
> >
> > The problem is that you're not sure that Hatari will always run in 
> > real time ; if you pause hatari, then your "real" keyboard will loose 
> > some bytes that can't be transfered to the emulated acia. Same 
> > problem if hatari slows down (for example emulating a falcon with not 
> > enough cpu on the host side) or if you press alt+x to go in fast mode 
> > : you won't have the same baud speed under emulation as the real HW 
> > expects.
> >
> > In the end, I'm not sure this kind of patch to mix real atari HW with 
> > emulated atari machines will work correctly.
> >
> > you can of course try it on your side and see what results you get, 
> > but it's not sure this can be merged into hatari if it imply too much 
> > specific changes.
> >
> > Nicolas