Electronics > Microcontrollers

"Tricks" to connect multiple push switches with minimum i/o usage.

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firewalker:
What "tricks" do you use to connect multiple push switches with minimum i/o usage?

Lets say you have to connect 10 push switches but you don't to spare to many i/o ports. I have seen some people implementing an r-2r ladder and pushing the output to the mcu's analog input. After that it's all software.

Jimmy:
You can wire the switches in a matrix to save inputs

How many switchs and how many inputs

firewalker:
Not a particular project. I just saw the r-2r method and opened this discussion.

Jimmy:
Cool

Their are many different options depending on the operation of device


To extent io you could use
RS232  1 pin simplex
I2C device 2 pin
Dallas 1 Wire 1 pin
Johnson counter 2 pin
SPI 4 pin

apex:
If you add a diode to each switch, you could charlieplex them.
Or add a 555 with a different frequency to each one and then measure the frequency as seen on hackaday

apex

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