On older versions of the RDDRONE-FMUK66, this port could only be used as IRDA. Since RDDRONE-FMUK66 Rev. C, it is by default configured as a free UART, which can be used as Telemetry 2 in PX4. It can still be reconfigured to use it as IRDA or as an extra I2C bus, though pull-up resistors will have to be placed by hand.
Pin | Signal | Voltage |
1 | VCC | +5.0V |
2 | UART TX | +3.3V |
3 | UART RX | +3.3V |
4 | GND | GND |
Rev. B (and older boards) are not supported anymore. This information is left for reference.
Pin | Signal | Voltage |
1 | GND | GND |
2 | UART RX | +3.3V |
3 | VCC | +3.3V |
4 | IR- | +5.0V |
5 | IR+ | +5.0V |