INAV Serial Gimbal and Serial Configuration

I. Introduction

INAV 8.0 introduced serial control support for Walksnail GM series gimbals. Compared to traditional PWM control methods, serial control offers the following advantages:

• Saves up to 4 PWM channels
• Controls gimbal behavior through modes
• More precise data communication and expansion capabilities
  However, the disadvantages are:
• Cannot enjoy the full flexibility of INAV Mixer like PWM (e.g., complex custom mixing).

II. Control Methods

✅ PWM Channel Control (Standard Control)

• Directly maps RC transmitter sticks/knobs to gimbal channels;
• Assign RC channels in Configuration → Serial Gimbal settings to control the gimbal's three axes;
• Unassigned channels default to center, the gimbal won't respond to input and operates by mode;
• Simpler wiring than PWM (saves 4 SERVO interfaces);
  ✅Headtracker Control (Enhanced Immersion)
• Must enable Gimbal Headtracker mode;
• Serial port receives independent Headtracker data, replacing RC input channels;
• Supports bidirectional serial port, FC TX connects to gimbal, RX connects to Headtracker.
  gimbal_serial_single_uart = ON: Allows one serial port on the FC to control the gimbal and receive headtracker data simultaneously.

III. Gimbal Modes (Set via Modes Page)

Mode Name	Description
No Mode (Default)	Default behavior similar to FPV or Follow mode; responds to flight attitude and user input
Gimbal Center	Centers and locks the camera, ignoring user input, suitable for restoring view or resetting orientation
Gimbal Headtracker	Switches to headtracker input, behaves like Gimbal Center when no headtracker is connected
Gimbal Level Tilt	Locks the gimbal's tilt axis to maintain the horizon, can be叠加 with Roll mode
Gimbal Level Roll	Locks the gimbal's roll axis to maintain level, can be叠加 with Tilt mode

IV. Gimbal Advanced Settings (Configurable via CLI)

Parameter Name	Description	Value Range
gimbal_pan_trim	Horizontal direction trim	-500 ~ 500
gimbal_tilt_trim	Tilt direction trim (commonly used for FPV pitch-up)	-500 ~ 500
gimbal_roll_trim	Roll direction trim	-500 ~ 500
Wiring Instructions

• Connect Walksnail Gimbal's serial port TX to FC's RX
• FC's TX can simultaneously output control signals to Gimbal, or use RX to receive Headtracker data
• If the serial port is used for both gimbal control and headtracker input, enable: set gimbal_serial_single_uart = ON

V. INAV Serial Configuration

5.1 Serial Port Type Overview

INAV supports multiple serial port types:

Serial Port Type	Description
VCP	Virtual serial port, directly connects to main controller chip via USB, no additional USB-to-serial module needed
UART	Hardware serial port, a pair of TX/RX pins, communication handled by hardware, most stable and efficient
SoftSerial	Software-emulated serial port, simulated through software interrupts, high resource usage, only for low-speed applications (e.g., low-speed telemetry)

5.2 Serial Port Uses

Serial ports can be used for different functions:

Function	Application Scenario
MSP	Flight controller communication (connecting to INAV Configurator)
Serial RX	Serial receiver (such as SBUS, CRSF, IBUS, etc.)
GPS	GPS module
Telemetry	Telemetry data (such as FrSky, MAVLink)
Blackbox	Blackbox data recording

5.3 Configuration Principles

1. Configure serial ports first, then enable corresponding features
2. Maximum of 3 MSP interfaces allowed
3. SoftSerial limited to 19200 baud rate, SOFTSERIAL feature must be enabled
4. Each telemetry protocol can only use one serial port (e.g., FrSky telemetry can only be used once)
5. Serial ports cannot be arbitrarily shared (MSP and Telemetry or Blackbox can be shared, other combinations are not allowed)

5.4 CLI Advanced Configuration Commands (For Advanced Users Only)

serial <port_index> <function_bitmask> <msp_baud> <gps_baud> <telemetry_baud> <blackbox_baud>

• <port_index>: Port number (usually starts from 0, e.g., UART1 is 0)
• <function_bitmask>: Function bitmask (refer to serialPortFunction_e in the source code)
• <baud>: Baud rate, refer to the table below for settings
  Baud Rate Number:
  | Number | Baud Rate |
  | --- | --- |
  | 0 | Auto (Automatic) |
  | 8 | 115200 (Common) |
  | 9 | 230400 |
  | 11 | 460800 |
  | 12 | 921600 |
  | 14 | 1500000 |
  | 15 | 2000000 |
  | 16 | 2470000 |
  ————This article is quoted from the official INAV website: https://github.com/iNavFlight/inav/blob/master/docs/Serial.md