Re: Keypad for Raduino...?

Arv Evans
 

Mark  N1VQW

I built a similar SNA, but control it via USB/tty link from a Raspberry-Pi. 

The keypad idea of using a single ADC input to decode keystrokes seems
intriguing to me.  This morning I set up the code so it uses a range of voltage
values for each key, and added a time delay for debounce.  using a voltage
range window seems to give me latitude enough for using standard value
resistors in the R-matrix.  Initially I set up the code to just show the value as
each key was pressed, then rewrote it to use those values as targets. 
I divided the difference between voltage values for each key by 2 and used
that to generate the tests for each key.  Code is not efficient yet as it is just a
bunch conditionals but once it is working I can go back and make it pretty. 
Next question is how much will RF affect the keystroke voltage readings?

This activity is generating some interesting thoughts about possibilities for a
new Raduino design...with OLED display, Keypad, Rotary Encoder, RTC,
Si5351a, and more.

Arv  K7HKL
_._



On Sun, Jun 24, 2018 at 11:34 AM Mark Pilant <mark@...> wrote:
Hi Arv.

I used a similar keyboard for a Scalar Network Analyzer I built.  (Before I
found out about the PHSNA :-)  It turned out to work very well.  I did run
into a few issues worth mentioning.

Make sure you have some form of switch debouncing (software or hardware) as
part of the design.  I had both in my design.   Also, make sure you take into
account the resistor tolerances when determining the analog value for any
given key.  (Part of my SNA design was a set of calibration tasks, one of
which was the keypad.)

I'm building a uBitx with a TFT, and may include a soft keypad to augment the
encoder.  (If I can find the time... too many projects :-)

73

- Mark  N1VQW

BTW, feel free to look at the SNA code: https://github.com/pilant/N1VQW-SNA




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