[Swlug] 4x4 keypads on the Pi

[Rhys Sage]

Is there an online meeting coming up soon? I might be able to attend but it won't be early. I'll likely be home about 5:30PM my time so likely not before 10:30pm - probably way past most peoples' bedtimes.

I'm loaded down with work and running for election. I'm still managing an hour or two most Sundays on my Pi Projects though.

I've just been experimenting with a 4x4 matrix keypad from China.The type that goes 0-9, A-D, * and #. I tried putting resistors on it and it mostly worked until I found two resistors were clearly duff and giving the wrong readings. My biggest issue has been the random numbers generated by the Pi ADC. Not, I think, the Pi's strongpoint.

Having abandoned the idea of 3 wires going to ADC_VREF, AGND and ADC0, I moved on to using 8 GPIO pins and polling the pins to see which button is pressed. That I'll try next. In the meantime I'm trying to find the correct Phew library as used by Kevin McAleer to turn the Pi Pico W into a captive WiFi portal. Sometime in the future the PCF8754 module from eBay China will arrive. That should mean I can just plug in the screen and keypad when needed for coordinate entry into my project.

Another step will be getting a motor controller working from the Pi Pico while connected to my brushless ducted fan motor.

At the moment it's all proof of concept stuff leading to development of my project. 


Rhys Sage