With a Picoblaze core in place, we spent this week implementing the analog interface for the receiver board, particularly the potentiometer and ADC control. The potentiometer protocol is somewhat more complex than the one for the ADC, but the frequency of actuation needed to control the input gain is also much lower than the sampling frequency. Therefore, this protocol was implemented partly in the Picoblaze code, for high level control of the existing hardware block implementing the I2C interface. The implementation was verified on-board, using special messages of the serial protocol. We did not yet test whether the actual gain of the chain was being correctly altered, only that the potentiometer registers were updated.

The ADC interface, relying on a simpler protocol of SPI messages, was implemented using only the existing hardware module, and tested by displaying the ADC output word on the vendor-supplied seven-segment display, with a DC source at the input. I wrote a buffering module for the ADC output, so that it is possible to load a continuous set of samples on the controlling PC for testing (instead of downsampling to fit the lower baud rate of the serial port), but this has not yet been tested.

Due to strong winds on Friday, we had to delay the scheduled tests for Monday, when conditions should be fairly calm.