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Overview

The OVERRIDE parameter group (specifically OVERRIDE_CHAN) configures the manual override safety feature for ArduCopter.

Key Concepts

1. The Override Channel

In some complex setups (like using a Joystick or external script for navigation), it is important to have a physical switch that "Forces" the autopilot to ignore the external inputs and return control to the pilot's RC transmitter.

  • OVERRIDE_CHAN: Specifies the RC channel (1-16) mapped to an "External Input Enable" switch.
    • Low: Autopilot uses external MAVLink control.
    • High: Autopilot ignores external control and follows the RC stick positions.

Developer Notes

  • Library: libraries/AP_RCProtocol.
  • Safety: Critical for testing new companion computer code; allows the pilot to "take back the drone" instantly if the software malfunctions.

IO override channel

OVERRIDE_CHAN: IO override channel

Description

If set to a non-zero value then this is an RC input channel number to use for giving IO manual control in case the main FMU microcontroller on a board with a IO co-processor fails.

Values

  • Range: 0 to 16
  • Increment: 1
  • Default: 0

Description

This parameter configures a safety feature for flight controllers with a separate I/O processor (IOMCU).

  • Function: If you assign an RC channel to OVERRIDE_CHAN, switching that channel high (>1750 PWM) will bypass the main flight processor (FMU) and give you direct manual control of the servos via the I/O processor.
  • Use Case: Critical for recovering a plane if the main flight code crashes or freezes. It allows you to fly manually ("stick-to-servo") using the backup I/O chip.
  • 0: Disabled.

Source Code

ardupilot/ArduPlane/Parameters.cpp

Output Configuration (OUT) Generic Custom Parameters (PARAM)