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I need to replace the keypad from this board with a Raspberry Pi or Arduino so I can control programmatically what keys are sent to the board (so I can automate keypad press, without having the physical keypad connected).

  • Can I just connect GPIOs (3.3 V) from a Raspberry to the socket board (in image #3) directly, so it can act as a keypad but programmatically? I'm afraid to fry the board.

  • Why are there 10 pins? Most keypads I have seen only have 7 pins.

#1 Keypad #2 Back of the keypad

The other end of the wire band where it is connected to the board HD picture of the board

HD picture of the board (under)

Thanks for your help

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    \$\begingroup\$ seven relays ... one for each row and column ... close one column and one row to assert a keypress \$\endgroup\$
    – jsotola
    Commented Nov 25, 2022 at 22:34
  • \$\begingroup\$ This is the plan I m gonna end up with yeah, thanks \$\endgroup\$
    – Owow
    Commented Nov 26, 2022 at 16:07
  • \$\begingroup\$ I have succeeded to identify which pin is which col/row and was able to trigger numbers with my breadboard. I just have now to find relays to do it automatically \$\endgroup\$
    – Owow
    Commented Nov 26, 2022 at 19:56
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    \$\begingroup\$ optoisolators may also work \$\endgroup\$
    – jsotola
    Commented Nov 26, 2022 at 20:34

1 Answer 1

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Unlikely, or it depends if you can figure it out yourself if you can or can not, as it may or may not be possible for various reasons.

The other board looks like has a programmable microcontroller, so it is scanning the keypad matrix. The connector may have 10 pins instead of 7 for various reasons. The matrix may or may not be arranged as a 3x4 matrix. The other pins might be unused or used for something, like ground, chassis, earth, or backlight or whatever. It is unknown until you figure out how the 10 pins are used.

Even if it just a 3x4 matrix, you don't know how it is scanned until you test it. It might be a part of a larger matrix. You also don't know if the matrix is scanned with 5V or 3.3V or some other voltage, until you figure it out.

Even if you figure it out, the speed how the matrix is scanned is also unknown, so it may be difficult to write software which reacts to correct scan outputs fast enough to simulate a button push. Might be especially hard with Raspberry Pi since it does not run a real time OS. Might be possible with Arduino if most of the time is spent responding to the scanned matrix pins, instead of other stuff.

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  • \$\begingroup\$ thank you for your answer, I ve added 2 more pictures that seems to show that only 7 pins are actually connected to the board. If it's not possible, do you have any ideas how I could automate what keys are sent? The micro controller is a PRO-328-P \$\endgroup\$
    – Owow
    Commented Nov 25, 2022 at 22:00
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    \$\begingroup\$ It still might be possible, if you have not done anything to confirm it either is or is not possible, since you have the board, we don't. PRO-328-P is not a microcontroller. It might be a name of some board with some microcontroller and other stuff, the name could indicate it has an ATMega328 or some variant. \$\endgroup\$
    – Justme
    Commented Nov 25, 2022 at 22:12
  • \$\begingroup\$ And what if I recreate the matrix pad but instead of using buttons, I use 3v relays that I can control with the arduino? and let the initial board send the signals for each column and use the arduino to open/close the correct row relay to let the signal through \$\endgroup\$
    – Owow
    Commented Nov 26, 2022 at 12:15
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    \$\begingroup\$ That's of course possible, but going around the original problem if it is possible directly. The relays don't have to be 3V relays. And analog multiplexer or analog switch ICs are quite a bit cheaper and consume much less current than relays. So you could use relays, but it might not be the smallest or easiest or cheapest solution. \$\endgroup\$
    – Justme
    Commented Nov 26, 2022 at 13:14
  • \$\begingroup\$ Thank you, I m gonna try with 2x 74HC4066 since they have 4 controllable switches with input/ouput \$\endgroup\$
    – Owow
    Commented Nov 26, 2022 at 15:53

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