I am a newbie in this world, so I would appreciate any kind of help.
I have an arduino MKRFOX1200 connected to an ADC (Texas Instrument PCM1808EVM) receiving a constant signal. The two boards are connected using the I2S communication protocol. With the oscilloscope I see there is a continuous signal in the SD (serial data) pins from both boards (Arduino and ADC), but when I use the I2S.read() function from I2S library at some point I stop receiving output. I do not understand what can be happening.
You need to post the code, using code tags, and clearly describe what happens and when. See the "How to post" instructions at the head of every forum topic.
I just got PCM1808 yesterday, it needs 2 voltages 3.3v for digital and 5v for analog part. It also needs master clock, regardless if you use it as slave or master. Arduino library does not provide master clock functionality and is not straight forward to hack due to class restrictions they decided to put on inheritance. ArduinoSound has example implementations, you should try those and make it work first.