Have the mixer RP2350 supply clock and sync on a single pair of lines, so it has lots spare for the I2S data. And if you really run out get one of the third party boards using the 80 pin variant. I actually send the control data down the I2S as well (who needs 32 bit audio in a synth !At first I was like, “Wait, seriously?” — but thinking about it calmly, it’s actually a really interesting approach. I’d like to explore it.Just a suggestion to you both - wire in two RP235xs linked by PIO I2S or TDM and an SPI bus. No matter how much you optimise the code, eventually you'll need more processing power to implement more features. Oscillators and envelopes in the first MCU and filters and effects in the second.
And this MCU only costs about the same as a few op-amps
Good luck !
A setup where multiple RP2350s each handle the audio processing for a few timbres/voices, and then feed their I2S streams into another RP2350 acting as a mixer, sounds pretty promising. The tricky part is that my synth already consumes a lot of GPIOs, so figuring out how to distribute pins and buses cleanly could get complicated.
Thanks for the suggestion!
) but that's up to you.And with the three PIOs you've potentially got 12 I2S busses but note that you may have to clock all the RP2350s from a common crystal to do so (alternative is large oversampling on I2S inputs but you'll still need to do sample rate correction at some point if each one isn't locked)
Statistics: Posted by MikeDB — Fri Jan 09, 2026 11:26 am