Assuming using the external memory bus will work as I hope it also open up the possibility of a low cost 2-4 channel, 8 bit Oscilloscope at 60-100Mhz sampling speed. Using discrete components I should be able to create a high speed ADC etc. This should be sufficient for a 10Mhz Oscilloscope where you have 6-10 samples per Hz at 10Mhz.
To avoid the 176 pin chips I could also do 2 channels on a Hat and simply add Hat’s to to create a Mixed Signal lab kit. It adds a bit of timing complexity to sychronize input from several Hat’s, but it should be doable.
As a hobbyist working with robots and motor controllers I seldom deal with frequencies above 1 Mhz, but I need multiple channels + I like the concept of a low cost Oscilloscope that can be programmed as open source. Using Raspberry PI for graphics means that my Oscilloscope can have a 1920 x 1024 (or even larger) mixed signal display with a standard HMI Interface.
The second side of this is that I can also create a 2 channel function generator with the same speed using a classic resistor ladder. This should be able to output programmable signal patterns at 5Mhz with 20 samples per Hz. I have dedicated chips that can deal with 40Mhz or higher, but those have limitation in patterns + I could add transistors to deliver 5Mhz with programmable Voltage and Effect.
Transferring data to Raspberry PI is an issue, but we can benefit from a faster SPI + we can filter data on the Hat because we only need to transfer as much data as we can display. This would make a heck of a lab kit if I can make this work.
I have a STM32F429 dev kit that I will test with to verify if this is doable.