Making good progress with implementing the feedback reading on the OpenDrop. With the feedback circuit correctly tuned (now using 15kOhm for feedback resistor R31) it is possible to read the full 128 electrode array in less than 20 Microseconds quite reliably. Drive voltage and layer thickness have some influence and need to be compensated.

See video of feedback in action:

Next up is to implement the feedback reading in a closed loop control algorithm for driving the electrodes.

Feedback circuit implemented on OpenDrop by:  Fobel et al., Wheeler Lab, University of Toronto