usb_audio icebreaker pinout in README.md

[dpavlin]

According top-icebreaker.pcf pinout in README.md should be:

• P1B3: USB DP
• P1B4: USB DN
• P1B1: Pull up. Resistor of 1.5 kOhm to USB DP

I tested it on my icebreaker board and it works for me.

I'm hearing noise when audio is quiet, is that expected or do I have dodgy wiring to headphones? (I don't have audio pmod, just direct connection to headphones)

[smunaut]

Mm, yeah, the pinout definitely need some update since there are several boards and several pmods / cable supported and you need to update the pcf to suit your exact needs.

And yeah, the noise can be normal, it's just PDM. Even with the pmod it can be heard a tiny bit. Ideally during silence periods the output would be ramped down to 0 (instead of 50% pdm) to avoid that. Definitey not HQ :)

Also I found on the icebreaker some digital noise also leaks through ...