07 · 12 min
GPIO, UART, and modules
3.3 V discipline, USB–UART, and using the Flipper as a talking stick for boards on your desk.
The 18-pin GPIO header is the least theatrical and most educational part of the device. It is a 3.3 V microcontroller breakout that can speak UART, I2C, SPI, and 1-Wire, and that can act as a USB–UART bridge. This is how you debug a board when you do not want to fish for a dedicated adapter.
Buses in one sitting
| Bus | Wires | Use on a bench |
|---|---|---|
| UART | TX, RX, GND (optional RTS/CTS) | Serial consoles, GPS modules, debug logs |
| I2C | SDA, SCL, GND, 3.3 V | Sensors, EEPROMs, small OLEDs |
| SPI | COPI, CIPO, SCK, CS, GND | Flash chips, some radios, displays |
| 1-Wire | Data, GND, power as specified | iButton, some temperature probes |
USB–UART lab
Put an Arduino, ESP32, or any 3.3 V MCU on the desk. Wire GND common, Flipper TX to the board RX, Flipper RX to the board TX. Open the USB–UART app (or the GPIO UART tool — names move; follow current official docs). Match baud. You should see boot logs. That single loop teaches more about hardware than a hundred replay videos.
- 01Common ground is not optional.
- 02TX goes to the other device's RX. People swap this every time. If it is silent, swap TX/RX once before blaming baud.
- 03Start at 115200 8N1 unless the datasheet says otherwise.
- 04Never attach to a vehicle OBD rail, a live mains supply, or a lock bus in a building you do not own.
Modules
Official and community modules (Wi-Fi developer board, video game module, NRF24, and so on) plug into this header. Install them from documented sources. A Wi-Fi module does not change the rules of engagement — other people's networks are still other people's networks.
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