Compatibility with ESP32 https://github.com/hpwit/SID6581 project

[pastam76]

Hi everyone,

First of all great project! I've got plain version 0.1 and DAC version 0.2 and they works pretty amazing with real C64. Dual SID feature is really useful. One of my favorite application is Cynthcart 64 which can use then 6 voices.

I'd also like to use it standalone as SID player and/or synth.

I was trying to make it working with ESP32 (https://github.com/hpwit/SID6581 and https://github.com/tobozo/ESP32-SIDView), but so far I wasn't much successful. Could it be because that those projects use HC595 shift registers to move data to SID? Seems that SK Pico might be sensitive to timing because I gave it a try with old DIY Atmel replacement which uses 32MHz crystal (probably some version of SwinSID) and it works ok.

Do you know what could be the problem? I was already playing with timing parameters, but the best I was able to get was very distorted sound. Also I was trying to source clock both from sw and dedicated 1MHz oscillator.

Regards,
Martin P.

[LouDnl]

I can tell you from my own experience of trying to make it work with SIDView by @tobozo that it will not work properly. I tried and failed, nothing to do with the sidkick tho. I didnt have a sidkick pcb yet, but when I did it didnt work either. Sidview works fine with real sids btw.
I ended up making USBSID-Pico
http://github.com/loudnl/USBSID-Pico

Here's a picture of my sidview tests:

[frntc]

It should not depend on the shift registers per se, but the SKpico is tailored a bit toward the signal timings on the C64 bus. You could experiment with the bus timings settings of the SKpico (or are these the timing values you already tested?), but I can't give hints which values might work. Regarding the source clock: do you use the DAC-version? There is a connection between clock and sample rate, which might result in buffer underflows/overflows when the clock is too far away from the PAL/NTSC-C64-clocks. This problem does not exist with PWM output.