Overview

The FEEDBAK parameter group (often appearing as CAM_FEEDBAK_ in the full parameter list) configures the high-precision Camera Shutter Feedback system.

For professional aerial mapping (PPK/RTK), it is not enough to know when the autopilot commanded a photo; you must know exactly when the shutter actually opened. This system listens for a hardware signal from the camera (usually via the Hotshoe or Flash port) to record a precise GPS time-stamp.

Key Concepts

1. Feedback Pin (FEEDBAK_PIN)

The GPIO/Digital input pin on the flight controller connected to the camera's feedback line.

2. Polarity (FEEDBAK_POL)

Defines whether the autopilot looks for a Low-to-High (Rising) or High-to-Low (Falling) voltage edge.

• 0: Active Low.
• 1: Active High.

Parameter Breakdown

• FEEDBAK_PIN: GPIO pin number.
• FEEDBAK_POL: Trigger edge polarity.

Integration Guide

1. Hardware: Wire the camera's hotshoe adapter to a digital input.
2. Config: Set CAM_FEEDBAK_PIN to the input pin ID.
3. Verify: Check the DataFlash log for CAM messages. The time difference between TRIG (command) and CAM (feedback) represents the total system latency.

Developer Notes

• Library: libraries/AP_Camera.
• Accuracy: This signal is handled via interrupt or high-frequency polling to ensure microsecond-level accuracy for post-processed kinematics (PPK).