After bodging in the correct connections to bring the -2.5V rail up (or down?) on the PyPPM 2.1 board, I finally got digitally selectable capacitive tuning working in the firmware and software.

The idea behind tuning is to place a capacitance in parallel with the sensor coil such that the resultant LC tank circuit resonates at a desired experimental frequency. Most devices have used manually adjusted capacitor banks or variable caps, but the PyPPM uses a digital control scheme that provides 64k unique capacitance values.

Check it out:

If everything goes well, I'll be able to run a field test soon of the non-adiabatic pulse program with and without tuning to show the performance in a real-world setting.

~ Brad.