2022-11-20 (Su) PoweredInlineSkatesRev2 Serial problem solution

I reconnected the Bluetooth units to USB → serial modules. I saw a problem where the radio connected to my motor-connected Arduino spat out a startup message to announce when it was "Connected." Unfortunately, the letter "C" can start the calibration routine where incoming speed data gets ignored. The other radio doesn't do anything, so I can swap them and eliminate that problem. When I reenabled the debugging data on my receiving side, I only saw zeros, even when I pushed the throttle.

I wanted to see what happened when the computer wasn't part of the operation, so I programmed the built-in LED to come on when there was data on the Bluetooth's serial port. As soon as I sent a command, the light turned on, then flickered continuously. I reconnected the computer, and the behavior didn't wait for an order. I repeated the test with the transmitting module unplugged, the receiving module unplugged, and even the Arduino unplugged. The activity light changed behavior depending on where I stood and whether I moved. The data was almost always zeros. I loaded the code to another Arduino, and the problem persisted. I loaded an example sketch that monitored serial activity on both ports and behaved the same way, so the problem wasn't solely with my code.

I thought the serial port was picking up stray data, and I could add a resistor that pulls the data line high or low. I considered how the Arduino acted the same in or out of the socket and ignored the Bluetooth module, so that could be a bad connection. Sure enough, when I checked the continuity between the Arduino and the radio, I found it missing. This was a case of a cold solder joint where it looks like a good connection but isn't. I reinforced the other data line, and my serial port and indicator light acted as I expected.
That shouldn't happen

The rest of the posts for this project have been arranged by date.
First time here?

Completed projects from year 1
Completed projects from year 2
Completed projects from year 3
Completed projects from year 4
Completed projects from year 5
Completed projects from year 6
Completed projects from year 7
Completed projects from year 8

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