Logic Analyser PS/2

[Anton]

Hi,

I am looking for extra "Custom" protocols for my logic analyzer beyond the built-in Signal, Bus, SPI, I2C, UART, CAN, I2S, 1Wire, HDMI. Specifically I need to decode a PS/2 stream.

Is there a library of ready-made scripts for other protocols? I have searched online and not been able to find it.

Alternatively, is there any documentation for how to code one, apart from the couple of coding examples?

Thanks,

Anton

[Anton]

PS. I have made a working basic solution by using a modified SPI setup as below:

 

But it would be far preferable to have detection of parity errors, start and stop bit errors, etc, as my other cheap, Chinese logic analyser does using PulseView/Sigrok.

[attila]

Hi @Anton

The PS/2 interpreter is not supported since it was considered obsolete.

Is this protocol still used in education?

[Anton]

Sorry, I didn't realise I needed to be in education to own one of these?

I am just an electrical engineer, with hobbyist needs at home, and thought I'd pick up one of these.

I see there is custom scripting available, so I imagined that "the community" might have made a few more plug-ins for common and less-common, or even largely obsolete protocols, ie MIDI.

Particularly since I see that Digilent also sell some kind of PS/2 dongle, I assume to allow keyboard interfacing.

[attila]

Hi @Anton

No, you don't need to be in education.
I only asked it to have an estimation on how many people would need such feature, where to put it on the priority list.

12-18 years ago, during my faculty years, the PS/2 it was already obsolete but still used in lab works.
I just asked some professors and students, it is not used since many years.

I will try to make an interpreter for you.

[Anton]

Wow, awesome! Thanks heaps! Don't put yourself to too much trouble on my account, as I have got a solution that sort of works. It just would be good to know how to make a full implementation.

For interest, I am having to reverse-engineer the keyboard on a late-90s industrial CNC machine. It uses the standard PS/2 protocol, but has a few customised buttons specific to the machine (as well as a bunch of extra LED's for feedback). These buttons output unusual scan codes that are not part of the three usual tables.

 

[Anton]

Hi Attila,

I was just getting back to this project, and wondering if there is any chance you've been able to make an interpreter?

The main issue is that when the host talks back to the PS/2 keyboard, there is an extra bit in the bitstream, which is causing my SPI hack above to get very confused.

Thanks again,

Anton

[attila]

Hi @Anton

Yes, see the latest beta version:
https://forum.digilentinc.com/topic/8908-waveforms-beta-download/

Edited August 27, 2021 by attila