Some important notes about this firmware:

There are two HEX files supplied. The file named "DAC with Bootloader (0110213A).hex" is the recommended software. This can be loaded into the dsPIC using a USB PICkit3 or other compatible PIC programmer.

If a later version becomes available, this can be copied to the root directory of an SD card and renamed to "DAC.hex". Insert the card and apply power. The unit will then re-flash itself. Note that you MUST then remove the SD card and delete the file or it will constantly re-flash itself and erase your settings as these are stored in flash.

An alternative file is also supplied, named "DAC with Bootloader and no power loss sense (0110213B).hex". The software normally monitors the low-voltage AC waveform for the correct frequency and automatically saves its settings and shuts down if there is a missed or short pulse. That way, if you switch the unit off at the wall, it will not lose any settings you may have changed and will resume WAV file playback where it left off (if applicable).

However, if you have bad mains noise, are running from a generator or are in a 60Hz area, this may prevent the unit from starting up properly or cause it to shut down during operation. In this case, you can re-program the unit with this alternative HEX file (using either an ICSP or via the SD card bootloader). The unit will then ignore the shape of the AC waveform and you will need to put the unit into standby before switching off at the wall for it to remember its settings.