2023-05-27 (Sa) KeyBoardolier Programming Care Bear Keyboard

I started a blank Arduino sketch to write a function to scan my inputs, but the results were all negative. I modified the test code to invert when it pulled the row pins high and low and turned off the pullup resistors. Instead of steady ON/OFF signals, the inputs were erratic or slowly pulsing, like they were periodically building a charge and discharging. When inputs react like this, the problem is usually floating terminals.

Test for key presses

I inspected my circuit, and my sketch worked when the rows were inverted because I installed the diodes backward for sinking (HIGH when the pin gets pulled to ground) outputs. Since I was using sourcing logic (HIGH when the pin sees voltage), I could not use the Arduino's built-in pullup resistors, but when I held a pulldown resistor to an input, I could read that channel clearly. I will install pulldown resistors and try again.

Testing a pull-down resistor

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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2023-05-18