I am using the ToneBoard as a normal DAC, just i2s -> Analog output.
It is totally working through the USB jack but I am trying to get it receiving its input signal from a Bluetooth receiver since it is going to be going inside a Bluetooth speaker.
Currently it hooked up through the 40 through holes,
BCK —> 29
SD -----> 33
LRCK --> 32
I think you will find that the I2S signals on the 40-pin connector (connector 6) are only linked through to the External I2S connector (connector 7), they do not get processed by the DAC. You can connect external USB data signals and/or 5v power to the 40-pin connector but not external I2S (or SPDIF, for that matter.)
I am also trying to access the I2S signals passing from the XMOS to the DAC but they (also) do not appear on any accessible external connector.