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4x4 Keypad via I2C? — Parallax Forums

4x4 Keypad via I2C?

ManAtWorkManAtWork Posts: 2,178
edited 2010-03-24 20:07 in Propeller 1
Hello,

there must be something like this. I'd like to connect a decimal keypad which is arranged in a 4x4 matrix to a propeller but I don't have enough pins left. Does anybody know a cheap keyboard IC that I can connect to the I2C port where the EEPROM is already attached? I could also programm a small AVR or PIC but I'd be happy if there's a simpler solution.

Thanks

Comments

  • T ChapT Chap Posts: 4,223
    edited 2010-03-24 14:51
    If you can't find a 4x4 keypad reader, you can use a PCF8575 which is a 16 i/o I2C expander, connect 16 buttons to it. Very easy to use. Read the precautions for setting pins to inputs.
  • localrogerlocalroger Posts: 3,452
    edited 2010-03-24 17:54
    You can actually get by with a pcf8574 8-bit expander and use 4 lines as outputs to scan the rows and 4 as inputs to scan the columns. There's not much extra code involved, it's cheaper, and would be compatible with matrixed keyboards.
  • nutsonnutson Posts: 242
    edited 2010-03-24 18:18
    http://ucontroller.com/index_pro1.html·has a 4x4 keypad with serial connection.
  • ManAtWorkManAtWork Posts: 2,178
    edited 2010-03-24 19:47
    Thanks to all. I think I'll take a pcf8574. It's smaller and cheaper than a pcf8575 and I don't have to proram (flash) it like a PIC.
  • BigFootBigFoot Posts: 259
    edited 2010-03-24 20:07
    Phillips and others have all kinds of inexpensive I2C parallel I/O chips available. We are using the PCA9535 which
    has 16 I/O bits but it is only $1.20 in 100's.

    Russ
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