Other Parts Discussed in Thread: PUREPATH-CMBEVM
I have a TAS5733LEVM board paired with a PUREPATH-CMBEVM motherboard and I'm playing wave audio files on the board using TI provided pure path console software. I intended on making a 24bit, 48k test wave with all the PCM data being filled with "X00" which to my knowledge correlates to no noise being output from the amp. Here's a screenshot of my file header and actual data to show these are set up correctly.
I then wanted to probe the LRCLCK, BitClck and I2S data line to see the bits being clocked in, what I expected to be all zeros in this case. Shown below is are the pins I'm probing on the 5733L:
However, I see random bits being clocked in. The pattern does not repeat, the following screenshot shows an example of this. I did not think it of importance to get a close up shot of a single frame because the bits seem to follow no pattern. Green is the left/right clock, blue is the bit clock and yellow is the I2S bus.
My question is does besides the PCM data get sent on the I2S line and does the PCM data get encoded somehow before being sent? Do I have an incorrect understanding of the I2S protocol, I have read all the supporting documentation I could find online. When playing this audio file the attached speakers produce no noise and the pure path audio player presents a flat waveform consistent with no audio. I have both channels loaded with 8ohm speakers and I am playing audio over USB. If anyone has any ideas or more information I could provide I would greatly appreciate it!
