JackOfAll wrote: > So the usual scenario, where basically you have two oscillators, one for > 44k1 and multiples and another for 48k and multiples. So from the audio > driver code, we just need to switch which is used to clock the outbound > I2S via a register, depending on the sample rate we are going to output?
Yes, two oscilator frequencies, one for 44.8 family the other for 48 family. There will be clock mux to select them, the output of the mux will go to the DAC chip, reclocking flops for the data, and into the processor to clock the data out of the internal FIFO. The ALSA driver needs to somehow tell the clock mux which frequency to choose, and also has to tell the I2S (and S/PDIF) circuits what the divider is from that clock frequency to sample rate. So 44.1 and 48 will have the same divider, but different mux select. The divider is set via a register inside the processor, but the mux select has to come out on a physical pin (and go across the EDM connector) I haven't looked carefully at the ALSA driver to see exactly how it does this, but these are the generic concepts. The ALSA driver may already be using a specific pin for the mux function, in which case I need to find out what it is so I can make sure it is on the EDM and hook it up on the board. John S. ------------------------------------------------------------------------ JohnSwenson's Profile: http://forums.slimdevices.com/member.php?userid=5974 View this thread: http://forums.slimdevices.com/showthread.php?t=97881 _______________________________________________ discuss mailing list discuss@lists.slimdevices.com http://lists.slimdevices.com/mailman/listinfo/discuss
