Been working on my SUNDAR in what little free time I have these days. Last night my Digikey order came in and I was able to get the dual channel digital potentiometer working. This will be used for a software AGC type circuit to adjust the offset and gain of the light sensor amplifier.
Interfacing to the MCP42010 was very simple. You simply SPI over a command byte and then a data byte. At 256 counts these parts will give fine control over the amplifier.
I also got the interrupt driven ADC code working for the controlling Arduino. Even with the floating point filtering and AGC code, I am able to get 6K samples per second. This is way more than I need for the SUNDAR. I was thinking more like 360 samples per rotation and 1-4 rotations per second.
After the next iteration of software development, the next issue will be the mechanicals. I did order and receive a set of slip rings from AdaFruit. But I will need to figure out a way to spin the rotating platform at 1-4 RPS. I would rather not use ferrous metals and electric motors, but that may be a pipe dream. Wind-up rubber band motor?
In the meantime, I have had conversations with Tautic Electronics on the lightning detector board I had purchased from them that did not work. Seems the unit had a cold solder joint and they are sending me a replacement. Hope it arrives today as we are due for thunderstorms.