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Patchbox OS and Pisound
I've been trying to get hold of some dev boards and IC's for a few months now and this global IC shortage is getting really annoying. I've got multiple projects held up for months now with what looks like months to go still before anything is in stock. I need the Raspberry Pi Compute module for example and it looks they won't be in stock until Q2 of 2022.
But, it does look like the Pisound boards may be coming back in stock so I was wondering if anyone has used them and Patchbox OS and what you think of it. I'd like to base a project that I have in mind for using iOS to control audio stuff on a mobile system and I'm wondering how difficult it is to setup the Pisound system and get going for people who don't have much Linux experience.
Comments
Pisound with Patchbox is a set and forget minimal friction os. The forum support is decent too.
True, it’s really a nightmare now. For my current DIY project, a controller for Model D, I had to order at 5 different shops to get all the parts. And this is just a Teensy board with a lot of knobs and buttons.
I really would like to build a fates device, which is a DIY Norns based on a RasPi plus a custom PCB board. Really cool project but probably a tough time to do that now. https://github.com/okyeron/fates
@krassmann you’d have to make the PCB yourself as Okyeron isn’t selling them anymore. If you see them on Reverb they’re likely fakes. If you want a DIY kit get the original Monome kit.
(can confirm as I bought one of the last boards from him last year)
That sounds promising. Thanks for the info. I'll order one of the boards when they come in stock then. I've got a Pi 4 already that I can use, so at least that shortage won't hold things back to start with.
The codec for the Fates project is at least still in stock at Mouser. I wonder how long it will be though since it is one of the Wolfsen devices from before they were bought by Cirrus Logic. I couldn't find the schematic or the Gerbers for the project. Was it an open hardware thing? Unfortunate if not because you could get them made at OSHpark or someplace similar if they were.
It did say in the readme for the Fates project that it would work with PatchboxOS too. Maybe you could get that running on a Pi and then get the physical UI parts for the Norns going there too.
I think it was meant to be open hardware. The schematics are in Adobe Illustrator format. There are ways to convert them to Gerbers but I never did that and this makes quite difficult for me.
It'd be quite a bit of work to do and then the board might not be right and would need some rounds of debugging. Probably easier to get it working with PatchboxOS if that does really look viable. If they get the I/O boards in stock soon, I'll do some playing around and see how hard it is to get some more physical controls hooked up.
@krassmann the https://llllllll.co/ forum is even friendlier (and more knowledgeable - at least regarding monome) than here. You could poke around there and see if you could get parts for your Norns etc.
The Pisound card is in stock and I've got one on order to play with now. They don't have many of them though. They got 85 in stock today and they are already down to 50. Apparently no end in sight for the IC shortage though -- saw an article this morning claiming that stability in supply won't come until 2024!
Should be here in a week or so and then I can figure out how to control it from an iPad. Should be fun anyway.
Congrats let me know what shenanigans you get into.
@krassmann & @NeonSilicon How much different is this board compared to a dedicated USB audio/MIDI interface, except that it connects to the native raspberry i/o header?
Loopback latency of the pisound board is given for a 128 byte sized audio buffer and fs=192k which is probably not the typical real world scenario either 😉
@rs2000 unfortunately I have no idea. I just find Norns very cool. Better ask the board developer. I linked to his github.
I don't know specifically what it is for this board in actual use yet. I'll try it out after I get the board. But the I2S interface is going to have some advantage over USB. For one thing, the USB audio device's MCU or CPU has to interface to the ADC/DAC IC too and that's probably going to be using I2S. So, the USB transport latency and the interrupts for the Pi's CPU are going to be on top of that.
I have one of the Elk Audio boards running on a Pi 4 and that has a ~1ms latency for reasonable buffer sizes and sample rates. It does have the real time Xenomai kernel running with the optimized interrupt system, so I wouldn't expect the Pisound to be that low level. But it is using a real time Linux kernel too.
I'll report back on how well it does after I've had some time to play around with it.
That'd be great! 👍🏼
The iQaudio Codec Zero, a $20 board with stereo i/o and up to 24bit/96kHz looks like an interesting and cheap alternative. For MIDI, I'd use the Pi's integrated Bluetooth or a USB MIDI cable or the Pi as a USB MIDI device, depending on the application.
Unfortunately I can't find any measurements for the Codec Zero, got a datasheet that states A-weighted SNRs of 90dB for the ADC and 100dB for the DAC - Not exactly high-end values on the ADC side but certainly good enough for building a decent stomp box.
BTW I've recently tried a demo FFT program on the Pi Zero that uses the GPU for high speed processing which IMHO enables its use for an apllication that can usually live with some inherent latency: An IR convolutor for doing reverb or delay effects, supporting IR lengths that wouldn't be possible with the Zero's CPU. The slightly reduced precision of the FFT implementation on the GPU could make the resulting sound a bit more grainy but hey, that can be a desirable effect 😉
I've seen the iQaudio boards but I haven't tried one yet. It's on my list of things to consider. The codec on it is aimed at low power mobile applications, so it's not going to hit the high end specs for sure, but it should be good enough for lots of applications. The HifiBerry DAC+ ADC boards are another one I'm thinking about. I've used one of their DAC's to do streaming to my stereo setup and I think it's been really good.
I haven't done any programming at all with the GPU on the Zero, but it does seem like looking at a reverb effect to bring in the GPU is a good place to get it to work. You can roll the added latency of the GPU into the pre-delay calculations to absorb part of that issue. Since you have all of the parallel processing capability there, you might be able to mix two or three different IR responses and get some good natural sounding reverb.
My eventual goal is to build a mobile battery powered device that has M.2 based storage and good audio I/O directly on the device, with USB, WiFi, Ethernet, MIDI, and Bluetooth. I want to be able to run the UI on an iPad and Android tablet but for all the audio and DAW related things to live completely on the headless external system. I'm focusing on the Pi's right now because I think they'll be good enough and it looks like the compute modules enable everything I need.
I finally got a chance to do some testing today with the Pisound using Patchbox OS. After some initial issues getting the OS updated and configured I did a latency test with using jack_thru on the Pisound card configured at 48 kHz and a buffer of 64. I sent a pulse through the RasPi 4 to one channel of my MOTU M4 on my Mac and a direct split of the pulse to the other channel on the M4. The latency measures at 5 ms for the roundtrip. I don't know how much processing I can get on the Pi with that buffer size, but that's a pretty good baseline to work from. It's looking good so far.
Sounds good @NeonSilicon!
Looking forward to hear what you can pull out of the Pi 4 CPU.