dkinzer
Site Admin
Joined: 03 Sep 2005
Location: Portland, OR
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Posted: 07 June 2007, 0:16 AM Post subject: Matrix Keypad Interface Using I2C |
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I've created an example of how to connect a matrix keypad to a ZX using a PCF8574A I/O expander on the I2C bus. If you have other I2C devices already attached, the keypad can be added without using any additional I/O lines.
The circuit schematic for the connection and example source code are attached. The code implements auto-repeat but does not handle "multi-key rollover". It implements a polling technique but you could use the interrupt output of the PCF8574A to implement an interrupt-based interface. I haven't thought through how you would implement auto-repeat in this case but it could probably be done using WaitForInterval() to implement the check for the key-still-down condition.
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| Keypad Interface Source Code |
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i2c_matrix_keypad.zip |
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i2c_matrix_keypad.jpg |
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