Audio noise

A project log for ESP-12F Raspberry Pi GPIO SDIO Wifi

Get fast Wifi via the Raspberry Pi GPIO header using the SDIO bus of the ESP8266. Also with audio jack for the zero.

jacksonliamjacksonliam 02/18/2016 at 18:501 Comment

I've got the headphone jack and audio in place. I'll update the instructions to make it simpler to setup.

Theres an intermittent high pitched whine and some faint clicking/crackling when nothing is playing, if you play something from one channel the other has lots of white noise.

WiFi (and possibly SD) access causes extra electonical noise.

Its good enough for playing sounds through a crappy speaker in a project, or for simple radio streaming (you don't hear the noise over the audio) but not for any kind of serious listening or for headphones.

I have filters the same as on the Pi 1, and I think my routing is OK. So the only thing I can think of is that the routing of GPIO12/GPIO13 on the Pi zero itself causes it to pick up noise. Or perhaps I need better filtering on GND?

I've tried it on a board with the 5v regulator populated too.

(I did populate all the audio filter passives)

On the positive side I routed the right and left channels the right way around, which I'm happy about as I was worried I'd mixed them up!


ajlitt wrote 02/18/2016 at 19:50 point

You're not going to get rid of that noise without a different design.

The PWM is powered from the same I/O supply as the rest of the CPU, so what you're hearing comes from other IOs transitioning.  The newer Pis use a separate regulator and a buffer to redrive the PWM into the filter, eliminating that noise.

  Are you sure? yes | no