The I2S example uses a loopback to check that data is transmitted and received correctly. As you can see in the prepare_tx_data() function, you can see that the device sends 0xCAFE, which is just zero values. Normally, a couple of initial samples sent by the I2S peripheral will have zero values, because it starts to output the clock before the actual data is fetched by EasyDMA. Since this example is dealing with streaming the initial zero, samples can be ignored.
So the output to the terminal upon successful transfers should just be 1: OK, 2: OK, and so on. If the SDOUT and SDIN pins are not shorted/wired to one another, then the following error will be output to indicate an error:
PS: The Holiday season is upon us, which will leave the Nordic support team understaffed until January 4th, 2021. This means that delayed replies will occur during this time. Sorry about the inconvenience and happy Holidays!
