RPM_MSG_RATE: RPM sensor message rate

Description

This is the rate RPM sensor data is sent in Hz. Zero means no send. Each sensor with a set ID is sent in turn.

Values

• Range: 0 to 200
• Units: Hz
• Default: 0

Description

This parameter controls the frequency of RPM telemetry messages sent by the AP_Periph device (e.g., a CAN-based RPM sensor or ESC).

• Usage: Set this to a non-zero value (e.g., 10Hz or 20Hz) to see motor or rotor RPM on your GCS or OSD.
• Function: The peripheral will sample the RPM and broadcast it on the CAN bus at this interval.
• 0 (Default): Disables RPM telemetry from this device.

DroneCAN RPM Message ID (RPM1_DC_ID)

Description

RPM1_DC_ID identifies which specific piece of hardware on the DroneCAN bus is providing the RPM data for this instance.

This allows you to map multiple DroneCAN RPM sensors (e.g., from different ESCs) to specific slots in the autopilot's telemetry system.

• 0: Auto-detection.
• Value: Specific Node ID.

RPM ESC Telemetry Index (RPM1_ESC_INDEX)

Description

RPM1_ESC_INDEX allows you to "Inject" external RPM data into the ESC telemetry system.

If you have a motor that doesn't provide internal RPM telemetry (like a gas engine or an older ESC), but you have an external RPM sensor (optical or hall effect), you can use this parameter to tell the autopilot: "Take the RPM from this sensor and record it as if it were coming from ESC X."

Tuning & Behavior

• Default: 0 (Disabled).
• Usage: Set to the motor number (e.g. 1) to have this sensor's data appear in the ESC[0] telemetry logs and GCS fields.

RPM ESC Telemetry Mask (RPM1_ESC_MASK)

Description

RPM1_ESC_MASK allows a single RPM sensor to represent multiple motors.

This is useful for vehicles where multiple motors are physically linked to a single shaft (e.g. a geared twin-motor setup) or for helicopters where one RPM sensor on the main gear represents the speed for the entire power system.

• Bit 0 (1): Motor 1
• Bit 1 (2): Motor 2
• Example: Set to 3 (1+2) if this sensor's data applies to both Motors 1 and 2.

Maximum Reported RPM (RPM1_MAX)

Description

RPM1_MAX is a safety filter to prevent "Spikes" or unrealistic data from affecting the autopilot.

Electrical interference or a loose sensor wire can sometimes cause a burst of pulses that look like the motor is spinning at an impossibly high speed (e.g. 500,000 RPM). If the autopilot used this data for a governor or dynamic notch filter, it could cause a crash. This parameter sets the "sanity limit" – any reading higher than this is ignored.

Tuning & Behavior

• Default: 100,000 RPM.
• Recommendation: Set this to roughly 20% higher than your motor's maximum possible physical RPM. For most small multicopters, 50,000 is plenty. For large gas engines, 10,000 might be appropriate.
• Context: Only applies when using GPIO-based (pulse counting) RPM sensors.

Minimum Reported RPM (RPM1_MIN)

Description

RPM1_MIN acts as a "Noise Gate" for the RPM sensor.

At extremely low speeds or when the motor is stopped, electrical noise on the sensor pin can sometimes look like a valid pulse, causing the GCS to show "Ghost RPM" (e.g. 2 or 3 RPM). This parameter tells the autopilot to ignore any calculated RPM below this value and simply report 0.

Tuning & Behavior

• Default: 10 RPM.
• Usage: For large, slow-moving rotors (like on a large helicopter), you might need to lower this to 5. For high-speed racing motors, you can increase this to 100 or more to ensure a clean zero-reading when disarmed.
• Context: Only applies when using GPIO-based (pulse counting) RPM sensors.

Minimum RPM Quality (RPM1_MIN_QUAL)

Description

RPM1_MIN_QUAL defines the "Certainty Threshold" for digital RPM sensors.

Some RPM sensors (especially those reporting via DroneCAN) calculate a confidence or quality score based on the stability of the signal. If the signal is weak or inconsistent (due to electrical noise or poor sensor alignment), the quality score drops. This parameter tells the autopilot to reject any data if the quality falls below this level.

• 0.5 (Default): 50% confidence required.
• 1.0: Perfectly clean signal required.

Tuning & Behavior

• Recommendation: Leave at 0.5. If you see your RPM readings "flickering" to 0 during high-speed flight, you may need to decrease this value slightly or check your wiring for noise.

RPM Input Pin (RPM1_PIN)

Description

RPM1_PIN tells the autopilot which digital port on the flight controller is connected to your RPM sensor (e.g., an optical sensor, a hall effect sensor, or the RPM output from an ESC).

• -1: Disabled.
• 0-103: The pin number assigned to the physical input.

Tuning & Behavior

• Default: -1.
• Setup: Refer to your flight controller's documentation to find the correct GPIO pin number for the port you are using.
• Requirement: Only used if RPM1_TYPE is set to 1 (GPIO).

RPM Scaling (RPM1_SCALING)

Description

RPM1_SCALING is the "Gear Ratio" or "Pole Count" setting for your RPM sensor. It tells the autopilot how many pulses from the sensor equal one full revolution of the motor or shaft.

$$ \text{RPM} = \text{Sensor Rate} \times \text{RPM1\_SCALING} $$

• Example (Hall Effect): If you have 1 magnet on the shaft, set Scaling to 1.0.
• Example (Pole Count): If using an ESC sensor on a 14-pole motor, the sensor sends 7 pulses per rev. Set Scaling to $1/7
  approx$ 0.142.

Tuning & Behavior

• Default: 1.0.
• Accuracy: Verify the reported RPM against a handheld tachometer. If the reported RPM is exactly double the actual RPM, divide your Scaling value by 2.

RPM Sensor Type (RPM1_TYPE)

Description

RPM1_TYPE enables real-time monitoring of motor or rotor revolutions per minute (RPM).

This is highly recommended for Helicopters (to monitor head speed) and for large Internal Combustion Engine (ICE) vehicles. It is also used by the Harmonic Notch Filter to dynamically track and eliminate motor-induced vibrations.

• 0: None. Disabled.
• 2: GPIO. For Hall effect or optical sensors connected to a digital pin.
• 4: Harmonic Notch. Derived from internal motor controllers (SITL/Special use).
• 5: ESC Telemetry. Averages RPM data from all ESCs reporting telemetry.
• 7: DroneCAN. For CAN-based RPM sensors.

Tuning & Behavior

• Reboot Required: Yes.
• Integration: Once enabled, you must configure the input pin (RPM1_PIN) if using GPIO, and the scaling (RPM1_SCALING).

DroneCAN Sensor ID

Note: This parameter functions identically to RPM1_DC_ID.

ESC Telemetry Index to write RPM to

Note: This parameter functions identically to RPM1_ESC_INDEX.

Bitmask of ESC telemetry channels to average

Note: This parameter functions identically to RPM1_ESC_MASK.

Maximum RPM

Note: This parameter functions identically to RPM1_MAX.

Minimum RPM

Note: This parameter functions identically to RPM1_MIN.

Minimum Quality

Note: This parameter functions identically to RPM1_MIN_QUAL.

Input pin number

Note: This parameter functions identically to RPM1_PIN.

RPM scaling

Note: This parameter functions identically to RPM1_SCALING.

RPM type

Note: This parameter functions identically to RPM1_TYPE.

DroneCAN Sensor ID

Note: This parameter functions identically to RPM1_DC_ID.

ESC Telemetry Index to write RPM to

Note: This parameter functions identically to RPM1_ESC_INDEX.

Bitmask of ESC telemetry channels to average

Note: This parameter functions identically to RPM1_ESC_MASK.

Maximum RPM

Note: This parameter functions identically to RPM1_MAX.

Minimum RPM

Note: This parameter functions identically to RPM1_MIN.

Minimum Quality

Note: This parameter functions identically to RPM1_MIN_QUAL.

Input pin number

Note: This parameter functions identically to RPM1_PIN.

RPM scaling

Note: This parameter functions identically to RPM1_SCALING.

RPM type

Note: This parameter functions identically to RPM1_TYPE.

DroneCAN Sensor ID

Note: This parameter functions identically to RPM1_DC_ID.

ESC Telemetry Index to write RPM to

Note: This parameter functions identically to RPM1_ESC_INDEX.

Bitmask of ESC telemetry channels to average

Note: This parameter functions identically to RPM1_ESC_MASK.

Maximum RPM

Note: This parameter functions identically to RPM1_MAX.

Minimum RPM

Note: This parameter functions identically to RPM1_MIN.

Minimum Quality

Note: This parameter functions identically to RPM1_MIN_QUAL.

Input pin number

Note: This parameter functions identically to RPM1_PIN.

RPM scaling

Note: This parameter functions identically to RPM1_SCALING.

RPM type

Note: This parameter functions identically to RPM1_TYPE.