So I am starting to work through all designs again. Specifically looking to rationalize the power supply regulators and reset circuits across all boards. And also to look for cheaper parts where possible.

The ADAU1966 DAC PCB may have an issues with the reset circuit. I used a 2.5V reset circuit (as the 2.5V rail is critical) which feeds the 2.5V output to the ADAU1966 reset pin. On several boards I have this works fine. The "trip" point should be 2.3V so some margin. However I have one ADAU1966 that is being a little fussy.

Some hindsight would have been good as a couple of transistors would have pulled the reset pin up to 3.3V. However now would seem like a good time to look for some cheaper/more universal reset supervisors (with open-drain outputs).

So I could not get any version of SigmaStudio to write to the EEPROM properly on Windows 10. Then it stopped communicating completely. I ran out of ideas at this point until I I thought about using Windows 7.

Luckily I have an old PC knocking around I was going to get rid of or re-purpose. Having found my spare copy of Windows 7 I installed this as a 32 bit version - although by accident having noticed I put the wrong CD in too late!

Anyway, SigmaStudio 3.14/3.14.1 beta don't seem to work properly for the EEPROM writing but communicate fine with the DSP. However SigmaStudio 3.12 seems to work just fine; I can write to the DSP and write to the EEPROM. When I selected self boot from EEPROM on the PCB jumper it starts up just fine.

Just have to remeber to have the jumper on the PCB shorted and "reset"/power cycle the DSP before writing to the EEPROM with I2C/SPI. You should also power up the DSP with the I2C/SPI USB adapter unplugged; and plug it in once powered. Also must remeber to set SigmaStudio to the correct EEPROM size.

I am also not seeing any random errors in the PANIC CODE section anymore which is good as I figured that all the DSP boards are unlikely to have issues.

So in short; Get Windows 7 (cheap keys on ebay?); install SigmaStudio 3.12; power up DSP board in the right mode; set up EEPROM size correctly and win!

Awesome!