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ArduPilot commissioning

Summary

ArduPilot commissioning on the Matek H7A3-SLIM covers four parameter groups that must be configured correctly before first flight: frame and motor setup, ELRS MAVLink mode on UART2, GPS and compass on UART3, and VTX power control via the switchable 9V BEC. Mandatory calibration (accelerometer, compass, RC, ESC) follows. The entire sequence is completed in QGroundControl; no command-line access is required. A commissioning error in any of the four parameter groups will prevent safe autonomous flight — working through them in order and verifying each before proceeding is the correct workflow.

Concept

Parameter groups and their dependencies

ArduPilot commissioning is ordered by dependency. Frame type must be set before motor test (DSHOT requires correct frame geometry for correct motor direction). ELRS MAVLink must be configured before RC calibration (the RC channel mapping is carried inside the MAVLink stream, not on a separate SBUS wire). GPS must be configured before compass calibration (the external compass on the M8Q-5883 is the only compass used; the FC internal compass must be disabled to prevent interference from motor noise).

The H7A3-SLIM has RC input pre-configured on USART2 (SERIAL2) with SERIAL2_PROTOCOL=23 (RCIN) by default. For ELRS MAVLink mode, this must be changed to SERIAL2_PROTOCOL=2 (MAVLink2). In ELRS MAVLink mode, the RC channel data is embedded inside the MAVLink stream — setting the protocol to RCIN will prevent telemetry from working while setting it to MAVLink2 handles both RC and telemetry on the same UART. This is the most common commissioning error on first Bandit builds. See → elrs-mavlink-mode for the full mode explanation.

Compass isolation

The H7A3-SLIM carries an internal compass. Motor current produces magnetic fields that corrupt compass readings during flight, particularly at the distances between the FC and the motors on a 220 mm frame. The external QMC5883L compass on the Matek M8Q-5883 mast is mounted 40 mm above the prop plane — sufficient distance for clean readings. Setting COMPASS_USE2=0 disables the internal compass entirely. Never run Bandit or Ghost with the internal compass enabled.

Reference

Parameter group 1 — Frame and motor

FRAME_CLASS,1 ; Quad FRAME_TYPE,1 ; X MOT_PWM_TYPE,6 ; DSHOT300 MOT_SPIN_ARM,0.1 ; Spin on arm for motor check MOT_THST_HOVER,0.35 ; Starting estimate; auto-learned after hover

SERIAL2_PROTOCOL,2 ; MAVLink2 — RC carried inside MAVLink stream SERIAL2_BAUD,460 ; 460800 baud RSSI_TYPE,5 ; Telemetry radio (ELRS MAVLink mode) RC_PROTOCOLS,512 ; CRSF enabled RC_OPTIONS,8448 ; Bit 9 + Bit 13 (ELRS-specific)

Parameter group 3 — GPS and compass (UART3)

SERIAL3_PROTOCOL,5 ; GPS SERIAL3_BAUD,38 ; 38400 for M8Q GPS_TYPE,1 ; uBlox COMPASS_USE,1 ; External compass (M8Q) COMPASS_USE2,0 ; Disable FC internal compass COMPASS_ORIENT,0 ; Arrow forward on GPS mast

Parameter group 4 — VTX power (9V switchable BEC)

RELAY1_PIN,81 ; GPIO81 = PC13 = 9V BEC on H7A3-SLIM RCx_OPTION,28 ; Assign to TX switch for VTX on/off

Procedure

Full commissioning sequence

  1. Flash ArduPilot (see → ardupilot-copter for flash procedure).
  2. Connect QGroundControl. Navigate to Vehicle Setup → Parameters.
  3. Enter parameter groups 1–4 in order. Write each group before proceeding.
  4. Mandatory calibration sequence: a. Accelerometer calibration (6-position, follow QGC prompts). b. Compass calibration (rotate aircraft on all axes until QGC confirms). c. RC calibration (verify all channels, confirm mode switches map correctly — see → ardupilot-flight-modes). d. ESC calibration if using non-DSHOT ESCs (Bandit/Ghost use DSHOT300; ESC calibration is not required).
  5. Motor test (QGC → Motors tab): confirm correct spin direction for X frame, props off.
  6. First hover test in AltHold, props on, open area: confirm altitude hold, confirm RTL on RC signal loss.
  7. Run Autotune in AltHold before first Auto mission. See → ardupilot-autotune.

Rationale

Splitting commissioning into four named parameter groups rather than a flat parameter list reduces the error surface for workshop builds. Each group has a single failure mode: if ELRS MAVLink is broken, RC calibration fails obviously. If GPS is wrong, Loiter refuses to engage. If the compass is not isolated, Loiter drifts on a predictable bearing. Named groups make the diagnosis path shorter when something does not work.

Connections

yaml requires: - [ardupilot-copter](<./ardupilot-copter.md>) - [elrs-mavlink-mode](<./elrs-mavlink-mode.md>) - [gnss-gps](<./gnss-gps.md>) - [barometer-magnetometer](<./barometer-magnetometer.md>) related: - [ardupilot-flight-modes](<./ardupilot-flight-modes.md>) - [ardupilot-autotune](<./ardupilot-autotune.md>) - [ardupilot-failsafe](<./ardupilot-failsafe.md>) - [software-commissioning](<./software-commissioning.md>) leads_to: - [ardupilot-flight-modes](<./ardupilot-flight-modes.md>) - [ardupilot-autotune](<./ardupilot-autotune.md>) - [maiden-flight](<./maiden-flight.md>)