Creating an audio input/output board for Raspberry Pi, Jetson Nano (audio input noise countermeasures)
Continue to connect the codec board created last time to the Raspberry pi and Jetson Nano and verify.
Audio input noise
Designing an audio input feels more difficult than outputting it.
When I operated the Raspberry pi with the audio input on Audacity in monitor mode, a big noise was observed. Increasing the bypass capacitor has no effect.
Assuming that there is noise including the ground potential, I investigated variously and found a chip called an isolator.
Looking at the ISO7641FM data sheet, the four signal lines are separated exactly, and the signal direction is conveniently only one opposite. I will make an isolator base using this. The secondary side is completely separated from GND, so a separate power supply is required. The codec board needs 5V and 3.3V, so 3.3V is generated from the regulator with USB5V input. I added an additional chip for server authentication.
The pattern design was created by separating the GND.
Insert it in a two-tier stack between it and Raspberry pi.
The effect uploaded the reference video.
I was able to eliminate the noise jump to the audio input by operating the screen.