lucian_dusk
Active member
Hello,
I'm having a bizarre issue with a custom audio board running a CS42448 codec.
After assembling the board, I got external audio on the TDM inputs running to USB audio just fine, then waveforms in the audio designer running to the TDM outputs as well.
I'm trying to combine them now and running into a weird issue: having all TDM input and output objects connected as in the sketch below causes a loud resonant feedback sound --- both through USB audio and TDM output. The sound stops as soon as I comment out the TDM input object (and associated patch cords).
A short audio sample recorded directly from USB audio
Strangely enough, I've narrowed down the issue to the first couple outlets of the TDM input. As soon as one of the inputs from the first even inputs of tdm1 is connected to mixer1, the feedback sound begins at a low amplitude. Connecting all four results in the full-blast sound as above.
![Screen Shot 2021-12-09 at 17.27.18.jpg Screen Shot 2021-12-09 at 17.27.18.jpg](https://forum.pjrc.com/data/attachments/23/23880-b7406f0043ea62d643614a3808f95f7c.jpg)
This passes clean noise to the outputs.
Here is the relevant part of the schematic.
![Screen Shot 2021-12-09 at 17.34.56.jpg Screen Shot 2021-12-09 at 17.34.56.jpg](https://forum.pjrc.com/data/attachments/23/23881-cd32032376a786ef3df99654d4882f14.jpg)
I now can't get any TDM inputs to pass thru to USB audio.
Has anyone run into this before? Any tips?
I'm having a bizarre issue with a custom audio board running a CS42448 codec.
After assembling the board, I got external audio on the TDM inputs running to USB audio just fine, then waveforms in the audio designer running to the TDM outputs as well.
I'm trying to combine them now and running into a weird issue: having all TDM input and output objects connected as in the sketch below causes a loud resonant feedback sound --- both through USB audio and TDM output. The sound stops as soon as I comment out the TDM input object (and associated patch cords).
A short audio sample recorded directly from USB audio
Strangely enough, I've narrowed down the issue to the first couple outlets of the TDM input. As soon as one of the inputs from the first even inputs of tdm1 is connected to mixer1, the feedback sound begins at a low amplitude. Connecting all four results in the full-blast sound as above.
![Screen Shot 2021-12-09 at 17.27.18.jpg Screen Shot 2021-12-09 at 17.27.18.jpg](https://forum.pjrc.com/data/attachments/23/23880-b7406f0043ea62d643614a3808f95f7c.jpg)
This passes clean noise to the outputs.
Code:
#include <Audio.h>
#include <Wire.h>
#include <SPI.h>
#include <SD.h>
#include <SerialFlash.h>
// GUItool: begin automatically generated code
AudioInputTDM tdm1; //xy=202,434
AudioSynthNoisePink pink1; //xy=312,214
AudioMixer4 mixer2; //xy=349,478
AudioMixer4 mixer1; //xy=350,371
AudioMixer4 mixer3; //xy=496,426
AudioOutputUSB usb1; //xy=674,634
AudioOutputTDM tdm2; //xy=686,426
AudioConnection patchCord1(tdm1, 0, mixer1, 0);
AudioConnection patchCord2(tdm1, 2, mixer1, 1);
AudioConnection patchCord3(tdm1, 4, mixer1, 2);
AudioConnection patchCord4(tdm1, 6, mixer1, 3);
AudioConnection patchCord5(tdm1, 8, mixer2, 0);
AudioConnection patchCord6(tdm1, 10, mixer2, 1);
AudioConnection patchCord7(tdm1, 12, mixer2, 2);
AudioConnection patchCord8(tdm1, 14, mixer2, 3);
AudioConnection patchCord9(pink1, 0, mixer3, 2);
AudioConnection patchCord10(mixer2, 0, mixer3, 1);
AudioConnection patchCord11(mixer1, 0, mixer3, 0);
AudioConnection patchCord12(mixer3, 0, tdm2, 0);
AudioConnection patchCord13(mixer3, 0, tdm2, 2);
AudioConnection patchCord14(mixer3, 0, tdm2, 4);
AudioConnection patchCord15(mixer3, 0, tdm2, 6);
AudioConnection patchCord16(mixer3, 0, tdm2, 8);
AudioConnection patchCord17(mixer3, 0, tdm2, 10);
AudioConnection patchCord18(mixer3, 0, tdm2, 12);
AudioConnection patchCord19(mixer3, 0, tdm2, 14);
AudioConnection patchCord20(mixer3, 0, usb1, 0);
AudioConnection patchCord21(mixer3, 0, usb1, 1);
AudioControlCS42448 cs42448_1; //xy=369,681
// GUItool: end automatically generated code
void setup() {
cs42448_1.enable();
pink1.amplitude(1);
cs42448_1.inputLevel(1.0);
cs42448_1.volume(.25);
AudioMemory(50);
}
void loop() {
}
Here is the relevant part of the schematic.
![Screen Shot 2021-12-09 at 17.34.56.jpg Screen Shot 2021-12-09 at 17.34.56.jpg](https://forum.pjrc.com/data/attachments/23/23881-cd32032376a786ef3df99654d4882f14.jpg)
I now can't get any TDM inputs to pass thru to USB audio.
Has anyone run into this before? Any tips?