From one problem to the next...
So the current ADAU1966 boards I am playing with have a new issue I have discovered. The ADAU1966 generates it's own "common mode" voltage reference to bias all the outputs to 2.25V. Two of the DAC boards I have tested at 1.47V on the CM pins.
Something is wrong here, it may be the extra capacitance I have on the pin. The data sheet recommends 10uF and 100nF. I have 100nf, 22uF (ceramic) and 220uF aluminium electrolytic. More is always better!!! Or not, in fact that is complete rubbish. I shall remove the 220uF and see what happens.
Extra PCB footprints are not an issue. It's all there to experiment with. If the changes are needed they are not really unexpected as with any project in development.
In any case, and I think I pointed this out in a previous post, the ADAU1966 seems to be hard to get now. The newer ADAU1966A is twice the price and just as hard to find in stock. Even so it is still a good DAC. I am working on a revised PCB layout, it would be good to make sure all designs (new and old) and up to their best performance and working 100%
That was hard work!
So after much head scratching the EEPROM selfboot is working again. The SPI address doesn't seem to matter as long as the EEPROM settings are correct. MP0, MP1, MP2, MP3 pins also need setting correctly - although I have changed these a few times before they are correct as it's not completely obvious.
This all needs documenting properly. Hopefully with this box of tricks now working, almost as expected pending a reduction in analogue output levels, I can start doing that.
Other reworked PCB layouts are still work in progress, a few more tweaks needed to finish them off.
CoreOne revision 2 is getting there. Component placement is 99% there, just need to move 4 jumpers to remove a break in a ground connection. Other PCB revisions are almost complete as well.
I still cannot get the EEPROM working on existing DSP boards. I am at a complete loss here. They used to work on early SigmaStudio versions. I shall keep poking away at it and there is a small hardware change I can try, removing a pull-up resistor on the EEPROM chip select line. I am not sure why it would make a difference now, but might be worth a try.
An electronics engineer and a long term electronics hobbyist. I like tinkering with stuff and making things.