By the way, since you are using the CM4, I have some previous projects with it which build a CM4 "sandwich". Here is a link to the github with all the projects. https://github.com/opencomputeproject/Time-Ap … bation/Hardware

ahmadexp wrote on 2024-05-17, 14:41:

Please don't drop the ESP8266. I love the retro modem so much.

Same! Maybe there’s a way to even integrated directly into the board but hey, I’m not designing it so it’s easy to make that when you don’t have to figure out where to squeeze it 🤣

ahmadexp wrote on 2024-05-17, 14:41:

Please don't drop the ESP8266. I love the retro modem so much.

The CM4 can easily emulate a modem, same as the ESP8266. 😉

Eivind wrote on 2024-05-17, 16:04:

ahmadexp wrote on 2024-05-17, 14:41:

Please don't drop the ESP8266. I love the retro modem so much.

The CM4 can easily emulate a modem, same as the ESP8266. 😉

See, that's why you get paid the big bucks! Can't wait to build one.

I noticed you have the CH559 chip on the schematic. I’m wondering since you have an RP2040 on the ITX for the HID that works nicely and the picoGus has the USB joystick functionality, couldn’t you leverage that for the HID somehow? It would save some space on the board.
Just a curiosity really.

snipe3687 wrote on 2024-05-19, 14:35:

I noticed you have the CH559 chip on the schematic. I’m wondering since you have an RP2040 on the ITX for the HID that works nicely and the picoGus has the USB joystick functionality, couldn’t you leverage that for the HID somehow? It would save some space on the board.
Just a curiosity really.

The PicoGUS firmware doesn't support USB-to-PS/2 translation, and even if it did you'd still only have a single port (the one currently used for joysticks). For two USB ports (like I use the RP2040 on the ITX-Llama) you need to leverage the PIO functionality of the RP2040. That's not available on the PicoGUS, because it's being used for ISA bus communication.

As for why I've used the CH559 instead of another RP2040 - mostly because it's a simpler and cheaper design. The only drawback is support for certain USB hubs - but rasteri is currently working hard on getting that improved in his HIDman firmware, and I'm helping out as best as I can. If it turns out that the RP2040 will be a better solution after all, I'll use that instead. I'm still working on basic component layout for the board, so there should be plenty of time to make changes if needed.

Eivind wrote on 2024-05-17, 16:04:

ahmadexp wrote on 2024-05-17, 14:41:

Please don't drop the ESP8266. I love the retro modem so much.

The CM4 can easily emulate a modem, same as the ESP8266. 😉

So, the CM4 is going to do MT32pi as well as retro modem?

ahmadexp wrote on 2024-05-19, 16:59:

Eivind wrote on 2024-05-17, 16:04:

ahmadexp wrote on 2024-05-17, 14:41:

Please don't drop the ESP8266. I love the retro modem so much.

The CM4 can easily emulate a modem, same as the ESP8266. 😉

So, the CM4 is going to do MT32pi as well as retro modem?

I wasn't thinking mt32-pi (though I suppose you could do that as well). But rather a standard linux distro with several services running.
The CM4 has more than enough IO and horsepower to do lots of things, it's not really necessary to run a bare-metal solution like mt32-pi. I think I've mentioned all of these before, but here's a recap:
2 x uart (3mbps) for modem/ethernet and floppy
1 x uart for midi input from the PicoGUS (running munt/fluidsynth/whatever software synth you want)
1 x i2s audio output
1 x i2c - for anything, really. the SOM and fan controller are also connected to this bus.

Eivind wrote on 2024-05-19, 17:15:

I wasn't thinking mt32-pi (though I suppose you could do that as well). But rather a standard linux distro with several services […]
Show full quote

ahmadexp wrote on 2024-05-19, 16:59:

Eivind wrote on 2024-05-17, 16:04:

The CM4 can easily emulate a modem, same as the ESP8266. 😉

So, the CM4 is going to do MT32pi as well as retro modem?

I wasn't thinking mt32-pi (though I suppose you could do that as well). But rather a standard linux distro with several services running.
The CM4 has more than enough IO and horsepower to do lots of things, it's not really necessary to run a bare-metal solution like mt32-pi. I think I've mentioned all of these before, but here's a recap:
2 x uart (3mbps) for modem/ethernet and floppy
1 x uart for midi input from the PicoGUS (running munt/fluidsynth/whatever software synth you want)
1 x i2s audio output
1 x i2c - for anything, really. the SOM and fan controller are also connected to this bus.

Oh that would be freaking awesome. If we can have a none bare metal emulation of MT32 with more features, that would be so awesome.
Please consider routing the CSI pins from the CM4 to a TC358743XBG. This will allow you to have HDMI input.
Ultimately, we can have the option of routing the video output (with the miniPCIe VGA solution with HDMI) to be sent remotely.
That will allow you to have your MS-DOS or Win98 box accessible via your very own KVM. Pi-KVM can be easily used for this purpose.
Just an idea though, but I think it will make the super awesome.

You know, regardless, I am a huge fan of your sequel of TinyLlamas and I am very thankful to you.

ahmadexp wrote on 2024-05-20, 03:37:

Please consider routing the CSI pins from the CM4 to a TC358743XBG. This will allow you to have HDMI input. Ultimately, we can […]
Show full quote

Please consider routing the CSI pins from the CM4 to a TC358743XBG. This will allow you to have HDMI input.
Ultimately, we can have the option of routing the video output (with the miniPCIe VGA solution with HDMI) to be sent remotely.
That will allow you to have your MS-DOS or Win98 box accessible via your very own KVM. Pi-KVM can be easily used for this purpose.
Just an idea though, but I think it will make the super awesome.

Heh, that is a very cool idea! Gotta say though - it seems quite niche, not sure it'd be worth it for most of the small (I assume) number of people wanting to build this thing... 😉
Do you think it might work to simply route the CSI lines out to a pin header, so one could plug in a small addon board for this specific use case? I mean, the CSI signal will be quite high-speed I think - do you know if this should be viable from a signal integrity perspective...?

Eivind wrote on 2024-05-20, 08:52:

ahmadexp wrote on 2024-05-20, 03:37:

Please consider routing the CSI pins from the CM4 to a TC358743XBG. This will allow you to have HDMI input. Ultimately, we can […]
Show full quote

Please consider routing the CSI pins from the CM4 to a TC358743XBG. This will allow you to have HDMI input.
Ultimately, we can have the option of routing the video output (with the miniPCIe VGA solution with HDMI) to be sent remotely.
That will allow you to have your MS-DOS or Win98 box accessible via your very own KVM. Pi-KVM can be easily used for this purpose.
Just an idea though, but I think it will make the super awesome.

Heh, that is a very cool idea! Gotta say though - it seems quite niche, not sure it'd be worth it for most of the small (I assume) number of people wanting to build this thing... 😉
Do you think it might work to simply route the CSI lines out to a pin header, so one could plug in a small addon board for this specific use case? I mean, the CSI signal will be quite high-speed I think - do you know if this should be viable from a signal integrity perspective...?

Oh yeah, if you put the standard CSI connector then it will be all good. Look at this module from Waveshare https://www.waveshare.com/hdmi-to-csi-adapter.htm

Eivind wrote on 2024-05-03, 09:23:

- Using an op amp for analog mixing of the two audio sources looks like an op amp not really needed for this simple mixing

Hi, PicoGUS creator here. Super cool to see this project as well as the LlamaBlaster, they have the perfect amount of audaciousness. 😁 Can't believe I didn't know about them until now!
I'd recommend using an op amp for the mixing... Using a 100% passive mixing circuit for the wavetable on the PicoGUS 2.0 is probably my only regret in the design. It sounds good but the volume level is definitely low. Usually you can just turn your speakers up more but if you're capturing for recording or streaming it can be annoying having to apply extra gain.

polpo wrote on 2024-05-22, 04:15:

Hi, PicoGUS creator here. Super cool to see this project as well as the LlamaBlaster, they have the perfect amount of audaciousness. 😁 Can't believe I didn't know about them until now!
I'd recommend using an op amp for the mixing... Using a 100% passive mixing circuit for the wavetable on the PicoGUS 2.0 is probably my only regret in the design. It sounds good but the volume level is definitely low. Usually you can just turn your speakers up more but if you're capturing for recording or streaming it can be annoying having to apply extra gain.

Hey Ian, kudos on your awesome project and congrats on getting it out on serdashop! 😀
Interesting about the mixing... Have you measured the output of the PicoGUS 2.0? What kind of Vrms / Vpp does it show when playing something at full (software-level) volume? I might add an OPA1656 or something, just wondering if it makes sense to add gain or if a unity-gain setup would suffice. For the first prototype of the LlamaBlaster I used a gain of 1.4, and that almost seemed a bit over the top, as the 1656 has plenty of current-driving capability.

Update:
I haven't had as much time as I'd hoped, so this has gone rather slowly - but I'm getting there.
It was just too tight getting the board down to the Raspberry Pi size (85x56mm), but it's not going to be very much larger at least.
Here's a screenshot of my current progress:

I still have a few components left to place and route, as you can see. I may also add an op amp and a CSI connector, shouldn't be a problem.

Update:
More or less done at this point, hoping to put in an order soon.

Edit: I added an op amp to the audio output stage, hopefully that'll make it more usable with directly attached headphones or speakers without a good preamp.
I still haven't tried to add the CSI connector, might give it shot later.

wow you really crammed a ton of stuff on there. looks good!

Very cool!

Amazing work Eivind. I was wondering, if you would be interested to route the D+ D- from the USB-C power to an FT232 and connect that to the CM4's ttyS0. That way you can have console access without adding anything much in terms of ports.

ahmadexp wrote on 2024-06-13, 23:06:

Amazing work Eivind. I was wondering, if you would be interested to route the D+ D- from the USB-C power to an FT232 and connect that to the CM4's ttyS0. That way you can have console access without adding anything much in terms of ports.

Wouldn't you just use ssh over wifi to connect to the CM4?

Eivind wrote on 2024-06-14, 14:13:

ahmadexp wrote on 2024-06-13, 23:06:

Amazing work Eivind. I was wondering, if you would be interested to route the D+ D- from the USB-C power to an FT232 and connect that to the CM4's ttyS0. That way you can have console access without adding anything much in terms of ports.

Wouldn't you just use ssh over wifi to connect to the CM4?

That is true. Though, imagine you have your system enclosed in a nice box and you have to change your wifi credentials. Connecting via ttyS0 you can go to the system and make all your necessary changes to get back on SSH. The fact that you do not support external SD card makes this even more necessary since you cannot pull your SD card and make necessary changes.