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Fully Featured Audio DSP Firmware for the Raspberry Pi Pico

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Re: Fully Featured Audio DSP Firmware for the Raspberry Pi Pico

#51

Post by Rohansi »

lysace wrote: post #32
Rohansi wrote: post #14

Earlier quoted context omitted.

The RP2350 (Pico 2) supports external PSRAM so you can add several MB more there if you need it.

Default specs matter a lot for worldwide availability and affordability, as well as for the willingness of people to spend a lot of time creating free software for it.

520KB of SRAM is actually on the high end for microcontrollers. It doesn't seem like much but SRAM is on-die and significantly lower density than DRAM. For comparison, it's the same type of memory used for CPU caches, which are also small!

You can easily find dev boards with 8MB of PSRAM online if you need it. Or you can buy the PSRAM and hook it up yourself. If you still need more memory than that then you're looking at the wrong chip for the job.

Re: Fully Featured Audio DSP Firmware for the Raspberry Pi Pico

#52

Post by mystifyingpoi »

hexmiles wrote: post #12

I wonder if you could do the same thing in reverse and have a cheap way to get multiple inputs. I would love a cheap way to add 8–16 inputs to my PC; all the audio interfaces I found cost quite a bit.

> a cheap way to add 8–16 inputs to my PC

The cheapest option is probably some Behringer mixer with enough inputs and multitrack interface over USB, like XR18.

Re: Fully Featured Audio DSP Firmware for the Raspberry Pi Pico

#53

Post by AnthonBerg »

hexmiles wrote: post #12

I wonder if you could do the same thing in reverse and have a cheap way to get multiple inputs. I would love a cheap way to add 8–16 inputs to my PC; all the audio interfaces I found cost quite a bit.

The Topping Pro audio interfaces have ludicrously good inputs. The E8x8 has eight analog ins and eight outs plus more connectivity for $450. It is very cheap for what you get. The inputs are crazy good. $450 is also a good chunk of cash, so…

https://topping.pro/E8x8-Pre/

For the $450 you get a lot of stuff. Preamps for mic and guitar pickups. Powerful headphone amp. It's clearly worth it if you make use of some of it, and potentially even just for the inputs alone. $450/8 = $56 per ludicrously clean input is good.

I bought an E1x2 kind of as a joke. Just to see how bad it was. It's actually really, really good.

And also:

It's actually possible to gang together multiple disparate audio interfaces. Let the audio stack keep them in sync with ASRC. Aggregate Device on macOS can do this. People say you can't but you can. Linux is good for this too. If you find a cheaper per channel input, this can actually be done; Piecemeal it.

Re: Fully Featured Audio DSP Firmware for the Raspberry Pi Pico

#54

Post by Rohansi »

mazurnification wrote: post #47
Rohansi wrote: post #43

Earlier quoted context omitted.

Can surely get more bandwidth but the it's less useful because it will not be directly accessible by the CPU anymore.

I believe PSRAM is directly accessible by CPU (there is even cache for PSRAM). Or am I missing something?

Lerc was referring to driving multiple PSRAM chips from a single Pico with PIO/DMA. The CPU will only work with a single PSRAM chip.

Re: Fully Featured Audio DSP Firmware for the Raspberry Pi Pico

#55

Post by SoleilAbsolu »

abhiraj_patwa wrote: post #42

Can I use this to connect my electric guitar straight to my pc, or use this DSP for guitar effects?

Looking through the GitHub and the AudioScienceReview link - this appears to be specifically about firmware features. You'd need to ensure that hardware inputs on device have input impedance of at least 250Kohms, probably closer to 1Megohm to prevent loading and signal loss if plugging guitar right in. I'd also assume (didn't see confirmation) that I/O is at line level, which is significantly higher than instrument (passive guitar) level, but this device can clearly add/adjust gain along the way. If you use active pickups with a built-in preamp like EMGs, it would probably work just fine.

Re: Fully Featured Audio DSP Firmware for the Raspberry Pi Pico

#56

Post by hexmiles »

AnthonBerg wrote: post #53
hexmiles wrote: post #12

I wonder if you could do the same thing in reverse and have a cheap way to get multiple inputs. I would love a cheap way to add 8–16 inputs to my PC; all the audio interfaces I found cost quite a bit.

The Topping Pro audio interfaces have ludicrously good inputs. The E8x8 has eight analog ins and eight outs plus more connectivity for $450. It is very cheap for what you get. The inputs are crazy good. $450 is also a good chunk of cash, so… https://topping.pro/E8x8-Pre/ For the $450 you get a lot of stuff. Preamps for mic and guitar pickups. Powerful headphone amp. It's clearly worth it if you make use of some of it…

Thanks for the suggestion. I was hoping for something cheaper since I don't need really high quality. For now, I'm using a bunch of cheap USB soundcards that are good enough, but having multiple USB devices makes routing hell.

Re: Fully Featured Audio DSP Firmware for the Raspberry Pi Pico

#57

Post by WeebLabs »

kcoul wrote: post #49
WeebLabs wrote: post #48

Earlier quoted context omitted.

Thank you! I will soon be producing a comprehensive introductory video on YouTube, which should make things more accessible. There will also be an official plug-and-play custom board that includes all of the relevant IO, connectors and codecs.

In the meantime, what would you recommend (if there's anything off-the-shelf that would work in a plug-and-play manner?) I had a project in mind that was waiting for something like this! :)

For USB input and SPDIF output, all that you need is a TOSLINK TX module(s) or a couple of capacitors and a resistor if you want coaxial SPDIF. For I2S output, the PCM5102A modules that you find on Amazon work very well, with very reasonable performance (SNR >100dB, THD+N ~95dB).

For 2.1 configurations in a pinch, the firmware includes a software DAC that's more than adequate to drive a subwoofer, so only one external DAC is needed.

Re: Fully Featured Audio DSP Firmware for the Raspberry Pi Pico

#58

Post by skybrian »

WeebLabs wrote: post #48
skybrian wrote: post #45

This looks very cool. Since a Raspberry Pi Pico doesn’t have built-in audio output ports, I think the main thing blocking ordinary people from using it is figuring out the hardware? A link to a tutorial for how to add audio output would be useful.

Thank you! I will soon be producing a comprehensive introductory video on YouTube, which should make things more accessible. There will also be an official plug-and-play custom board that includes all of the relevant IO, connectors and codecs.

Uh, some people like videos but I'd really rather have a web page with all the steps laid out and still photos. (And maybe links to the video, too?)

A custom board sounds great, too.

Re: Fully Featured Audio DSP Firmware for the Raspberry Pi Pico

#60

Post by Lerc »

Rohansi wrote: post #54
mazurnification wrote: post #47

Earlier quoted context omitted.

I believe PSRAM is directly accessible by CPU (there is even cache for PSRAM). Or am I missing something?

Lerc was referring to driving multiple PSRAM chips from a single Pico with PIO/DMA. The CPU will only work with a single PSRAM chip.

Yes, I was thinking of it more like bank switching.

Although, going back to the start of the thread where the suggestion was adding more RAM to future chips perhaps the request could be for support for multiple channels in the future.

It;s the age old question of parallel Vs serial Vs multi channel serial.

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