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Add MOSFET support to Wiegand app.

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Derek Jamison
2023-05-02 13:02:09 -04:00
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gpio/wiegand/README.md
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This application supports W4, W8, W24, W26, W32, W34, W37 and W40 formats.
This application can be used to test Wiegand readers and keypads. It can
save the data to a file, and can load and replay the data. Timings are
measured and displayed; which can be used to help debug Wiegand readers.
This application can be used to test Wiegand readers and keypads. It can save the data to a file, and can load and replay the data. Timings are measured and displayed; which can be used to help debug Wiegand readers.
## Wiring
The D0 and D1 wires of the Wiegand must be about 1K or higher for the Flipper to be able to effectively pull them down to ground. If the line has a lower resistance, like 100 ohms, then you need to add MOSFETs to help pull the lines low. The following [YouTube video](https://youtu.be/OVyd3ffnZ0M) is a demonstration of how to correctly wire the device.
In all configurations:
- Pin A7 goes to your Wiegand D1 (white) wire.
- Pin A4 goes to your Wiegand D0 (green) wire.
- Pin GND goes to your Wiegand GND (black) wire.
This is sufficient for reading signals with both this application and the Debug Accessor application.
If the pull-up resistors on your card reader are less than 1K, you also need the following:
- Two additional MOSFETs are required. I used IRF540 (but perhaps IRL540 would be better?)
- Two additional Pull-down resitors are required. I used 5K, but 4.7K would be fine as well.
- I'm still learning, but perhaps a MOSFET driver / optocoupler would provide even more protection to the Flipper GPIO pins? Use this circuit at your own risk. :)
Here is how you wire up the MOSFET and the pull-down resistors:
- The source pin of each MOSFET connects to ground.
- The gate pin connects to one side of a resistor. The other side of the resistor goes to ground.
- For the MOSFET used for D1:
- The gate pin of the MOSFET for D1 goes to pin A6 on the Flipper. (It should also already be connected to the pull-down resistor)
- The drain pin of the MOSFET for D1 goes to pin A7 on the Flipper.
- For the MOSFET used for D0:
- The gate pin of the MOSFET for D0 goes to pin B3 on the Flipper. (It should also already be connected to the pull-down resistor)
- The drain pin of the MOSFET for D0 goes to pin A4 on the Flipper.
## W4: 4-bit Wiegand