The fmu app configures the FMU board. It controls the multi-function mappings of a number of pins that can be used with different functions.

Update Rate

If FMU is configured for PWM outputs, the update rate can be set with the pwm -u parameter:

fmu mode_pwm
pwm -u 400 -m 0xff


To assign a given port mapping, the app can be called with these parameters:

  • mode_gpio – Configures all six multi function pins as GPIOs
  • mode_serial – Enabled the blue USART2 RX and TX plus the green USART2 RTS and CTS
  • mode_pwm – Enables SRV1-SRV4
  • mode_gpio_serial – Enables the red function mapping for the PX4IOAR board
  • mode_pwm_serial – Enables the blue USART2 RX and TX pins plus SRV2 and SRV3
  • mode_pwm_gpio – Enables SRV1-SRV4 and GPIO_EXT1 and GPIO_EXT2

To set a specific configuration, call fmu like this:

nsh> fmu mode_gpio_serial

Note that the EXP and MULTI connectors share a number of pins. Same names / colors imply the same pin. Pins on the MULTI connector are always ESD protected / level shifted, pins on the EXP connector are mostly on the 3.3V MCU voltage and unprotected.

EXP (Expansion) Connector Multi Port Mappings

MULTI (Multifunction) Connector Multi Port Mappings

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