Serial Ports

TELEM1, TELEM2 and SERIAL4 are available as general serial ports. TELEM1 defaults to 57600 baud. TELEM2 can be activated by setting SYS_COMPANION to 921600 (other baud rates are not supported, use a custom script if needed). SERIAL4 is used by some sensor drivers, but not used by any code / app started by default.

The following table gives the relationship between the output of this command and the uart devices:

/dev/ttyS0 UART1 (NSH console) IO DEBUG (RX only)
/dev/ttyS1 UART2 TELEM1 (USART2)
/dev/ttyS2 UART5 TELEM2 (USART3)
/dev/ttyS3 UART6 GPS (UART4)
/dev/ttyS4 N/A N/A (UART5, IO link)
/dev/ttyS5 N/A SERIAL5 (UART7, NSH console do only use as console)
/dev/ttyS6 N/A SERIAL4 (UART8)

Common UART Pinout

Pixhawk FTDI
1 +5V (red) N/C
2 Tx (out) 5 FTDI RX (yellow) (in)
3 Rx (in) 4 FTDI TX (orange) (out)
4 CTS (in) 6 FTDI RTS (green) (out)
5 RTS (out)2 FTDI CTS (brown) (in)
6 GND 1 FTDI GND (black)

Radio Control (RC)

S.BUS and S.BUS2 receivers should be connected to the RC.IN port, not the S.BUS port (which is the S.BUS output, not input)

PWM ESC / Servos

Pixhawk doesn't provide power on servo rails. To power servos connect external BEC to servo rail.

MAIN OUT should be used to connect all servos and ESCs (AUX OUT can be used in custom setups to drive additional servos or other peripherals).

Digital Airspeed Sensor

Digital airspeed sensor PX4AIRSPEED should be connected to I2C port. Use I2C splitter to connect multiple devices.

External USB Port

External USB port can be mounted on the outside of the plane / copter / rover and provides convenient access.

External Multicolor LED

External multicolor LED connects via I2C and has the same functionality as the in-built led and can be mounted anywhere on the system.

I2C Splitter

I2C splitter allows to connect multiple peripherals to the I2C port, including the external compass on the GPS.

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