This paper introduces a few new methods of scanning small keyboards, using fewer GPIO pins.
Pat Beirne
134cc7c02f
Update 'keypad_to_microcontroller.md'
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| 3x4_4pin.png | 10 months ago | |
| 3x4_4pin.sch | 10 months ago | |
| 3x4_5pin.png | 10 months ago | |
| 3x4_5pin.sch | 10 months ago | |
| 3x4_6pin.png | 10 months ago | |
| 3x4_6pin.sch | 10 months ago | |
| 3x4_7pin.png | 10 months ago | |
| 3x4_7pin.sch | 10 months ago | |
| 3x4_res_ladder.png | 10 months ago | |
| 3x4_res_ladder_diag.sch | 10 months ago | |
| LICENSE | 10 months ago | |
| README.md | 10 months ago | |
| direct_to_pin.png | 10 months ago | |
| direct_to_pin.sch | 10 months ago | |
| keypad_to_microcontroller.md | 10 months ago | |
| notes.txt | 10 months ago |
README.md
Keypad Scanning
The 3x4 and 4x4 matrix keyboards are commonly used for user input. Usually, the row and column wires are connected to GPIO pins on a microcontroller. A simple approach requires 7 wires for a 3x4 keypad.
This article introduces a new technique wish reduces the number of GPIO pins down to 6, 5 and even 4, using software scanning techniques and diodes.
Even though this reduces GPIO pin requirements in a manner similar to charliplexing, this is a different design.