ProtoDAC TDA1387 X8 project

[Tim Curtis]

@hifinet quick question- How does clocking/re-clocking work with ProtoDAC? Typically if you are using a re-clocker like FifoPi the DAC is better run in SYNC mode, for which there is a wire that connects between the reclocker and the DAC (Master clock MCLK terminals on both). But there is no such MCLK terminal on ProtoDAC. In that case is it running in asynchronous mode. Curious how it is getting the clock signal from Allo or Fifopi

The ProtoDAC simply receives data thats already been clocked upstream for example by Raspbery Pi itself or by a reclocker inbetween the Pi and the ProtoDAC. The data includes the clock signal and the DAC locks to that signal for its timing.

The IanCanada DAC boards are based on ESS 9028/38 chips and provide on-board re-clocking via a dedicated clock module. These boards by default can be used without a reclocker but if an IanCanada reclocker is used it provides an option to use its clock module instead of the DAC on-board module. This is done by removing the DAC on-board clock module and then connecting to the reclocker clock module via a coax cable.

There are some other subtleties in the ESS chip having to do with bypassing its integrated Jitter Eliminator (an Aschronous Sample Rate Converter or ASRC) which in effect is redundant to an external reclocker like the IanCanada FIFOPi. I think this is mentioned in one of the IanCanada documents.