ESP32 Forum

Good Morning,

i want to implement a slow speed pcm slave interface capable of transfering 32bit frames with 8kHz In- and Output at the same time. When i got my ESP32 i tried to (ab)use the I2S interfaces for that. I made more ivestigations Friday. There is my open thread you can find under: http://www.esp32.com/viewtopic.php?f=2&t=819 The idea was to use both I2S Interfaces as slave devices with connected ws and bclk, ones as Input and one as output. The slave mode didnt work, so i tried to make the pcm part for my self.

I created 2 buffers like this:

Code: Select all

 char *outBuf = pvPortMallocCaps(DATA_BUFFER_SIZE, MALLOC_CAP_8BIT); 

These buffers i uses in between the "self implemented" pcm interface and the uart. The uart itself does not use the output ringbuffer or interrupts, data will be written directly to the from the buffer above. All incoming data from the uart will be written the dma input ringbuffer and the copied to a buffer i declared like the output buffer above. But it does not matter if the data will be copied to this buffer or not, a random interruption of about 125us will occur in the moment the uart recieves any data. So its pretty possible that the DMA transfer to the uart ringbuffer may block the memory bus. I dont know if my buffers will be created in the 32k region which cpu1 also uses.

I think its a way bether solution to try on with I2S. Maybe i did something wrong, but at the moment this interface does not react on external clock signals in slave mode. I dont have a master clock. Only ws, bclk, din and dout from an other device.

Kind regards