I2S strange behaviour

RE: I2S strange behaviour

João Oliveira — Thu, 17 Feb 2022 12:24:53 GMT

We were able to get this working by changing R29 to a higher value.

Somehow, the switching of Q6 with such a low value resistor was interfering with the I2S block.

RE: I2S strange behaviour

João Oliveira — Fri, 04 Feb 2022 14:29:17 GMT

I validated the signals before and after the shifter. Everything seems fine, I can see the SCK, LRCK and the output from the microphone but we do not get any output from the I2S driver.

Another strange thing is that when I do not have anything connected to the I2S pins, the driver would give out zeros, as expected. When I assemble the device in the mainboard, this behaviour stops happening, even if we do not have the microphone connected,

Nevertheless, you can find a screenshot of the shifter configuration below:

The SCK and SDIN of the I2S are connected to TX2 and RX2 respectively. The nRF pins 1.00 and 0.24 are connected to nRFTX2 and nRFRX2.

The LRCK pin is connected to CS2 and CS2nRF is connected to pin 0.16.

I checked with the hardware designer but we could not find anything wrong with this configuration.

RE: I2S strange behaviour

ketiljo — Fri, 04 Feb 2022 11:53:37 GMT

Are you sure the level shifters are connected the correct way? As far as I can see, the SN74AXCH4T245RSVR have directional level shifters.

Can you post a schematic?