Using a touchtone phone keypad as a numeric input to an arduino

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I am trying to utilize an older touchtone phone to input a numeric code into my arduino UNO R4. Does anyone have an easy way to do this?

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You will need to figure out which pins correspond to the rows and columns. If you have a multimeter you can put it In continuity mode and make yourself a map of each key. Then you can look into the Keypad library. There are dozens of tutorials on it that will help you. Good luck :+1:

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p.s. forget the Touch Tone part… all you’re going to use is the keypad matrix.

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  • Suggest you use a new inexpensive 3X4 keypad.

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So I do have the matrix worked out, however, there was no continuity. I was able to get a resistance for each so I do have all of the wiring figured out with the keypad. But when I would press the buttons, I would get sporadic data.

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You are correct, it would be simpler, however...I am trying to utilize this phone to enter a key and although it is pushbutton, it is in the same shape (round) as a dial phone.

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  • You will need to take an ohmmeter out and figure the column and row connections.
  • Make sure there are no resistive connections between any row or column.
  • If your keypad doesn’t exhibit a simple matrix, your problem has then multiplied.
8

yes, I have that figured out, however, there is a resistance for each number/key pressed. These were the measurements in ohms.

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Then you can/could use analogRead()

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That's probably normal for a keypad of this type. Might help to clean the contacts. But there is enough current to drive a digital input.

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Yes I think any of those resistances would still pull a digital input_pullup pin "low" when pressed.

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