My apologies for the delay in reporting. Last week my AC died and I had to get a whole new system $$$. Having no AC in Florida in June is not good for my productivity.

I finally finished up with the receiver circuit. First I experimented with the spacing between transiter and receiver. See picture below. I decided to reduce the distance from 4 inches to 3.5 inches.

Then I found that the output of the receiver circuit was too low in the default state. This meant that the PICO always saw a logic one. I fixed this by adjusting the resistor values so the output defaults to about 0.5V.