PmodI2S2

[wchao_iris]

Hi I'm using Pmod I2S2 with STM32F407 for an audio application. 

Here is my setup. Audacity audio sound file is played on a laptop, and transmit through audio cable connected through the line-in port to the ADC on PmodI2S2, then through I2S, go through STM32F407 via DMA (where there are some signal processing code), then through I2S go to the DAC board on PmodI2S2 and then output the sound using a headphone.

But so far I only hear static, nothing else. 

I tried to use Analog Discovery 2 to debug, the signal frequency on LRCK and SCLK seems to be correct, with LRCK being 94KHz, and SCLK being 6144MHz. I also tried to use the I2S protocol analyzer, the SDIN and SDOUT signals look OK too, but I don't know if these signals are indeed correct. Is there anyway I can play these signals on Waves to see if they are correct?

Also is this the correct way to use PmodI2S2? I use a 3V output from STM32F407 board to power the PmodI2S2, the actual voltage I measured is around 2.9V. Any tip on how to debug this application is very much appreciated!

Thanks in advance for your help!

[JColvin]

Hi @wchao_iris,

You will likely need a higher voltage for the Pmod I2S2; the Analog to Digital converter chip (CS5343) has a minimum recommended operating voltage of 3.1V, so it will likely not operate correctly when you are trying to debug/listen to incoming analog signals. Is the SCLK clock you listed supposed to be 6.144 MHz? Since I suspect it is not over 6 GHz.

Thanks,
JColvin

[wchao_iris]

Hi JColvin,

Thank you so much for your reply! Yes, it is a typo, SCLK should be 6.144 MHz. And your answer solved my problem. I moved the power to 5V output of the board and it worked! Now my question is: is it safe to operate PmodI2S2 at 5V? Also, now that I can hear the music, there is still quite a lot of statics. Any suggestions on how to get rid of them? Thanks very much!

[attila]

Hi @wchao_iris

The noise on such audio interfaces is usually due to ground loops, rather analog than digital problem.

With AD2 you can analyzer the timing of such digital signals. For 6MHz signal you need at least double, 12.5-20MHz capture rate. The record-streaming function is limited to about 1MHz. With the 16k AD2 buffer (w 4th device configuration) at +12Mhz you can capture only about 1ms data.