Measuring I2S with Cheap Scope

I decided to to some audio measurement with the scope. Measuring I2S was the perfect exercise as the different clocks are sent in separate wire. Because of the limited bandwidth of the scope, choosing the slowest clock was necessary. A quick look at the I2S specification indicated that measuring the LRCK, the clock that tells you left channel data and right channel data was the line to measure.

Because in a single cycle LRCK indicates the transfer of data for a single stereo sample (left channel and right channel), LRCK always matches the sample rate. See Wikipedea for a better explanation.

Here is the measurement when iTunes plays at 44.1KHz sample rate



Here is the measurement when iTunes plays at 88.2KHz sample rate



Here is the measurement when iTunes plays at 96KHz sample rate