RoboT C-20S Single Axis FPV Gimbal

Using this Manual – Legend

Revision History

Caution
Always stay alert when using C-20S Single-axis Gimbal and its accessories to control an unmanned aerial vehicle (UAV) or other carriers. Careless may result in serious harm to yourself and others.

1. Make sure that the external power supply for the gimbal is a lithium battery (2S~6S) with an input voltage between 7.4V~26.4V. Otherwise, the gimbal may work abnormally or be damaged.
2. DO NOT short circuit the power output and GND. Otherwise, the equipment may be damaged and may not work properly.
3. Follow the instructions in the user manual when installing the gimbal. Incorrect installation may cause the gimbal to not work properly.
4. Make sure that all connectors are secure and all parts are work properly.
5. Make sure you fully understand and abide by local laws and regulations before using this product.
6. This product is not intended for children.

Diagram

Accessories

Installation

C-20S-O3

1. Remove the cover of the coaxial cable on the bottom of the air unit, then use the crowbar to disconnect the cable from the air unit and remove it.
   The coaxial cable and its connectors are vulnerable. Please be careful when disconnecting and connecting the cable.
2. Thread the camera’s coaxial cable out of the groove on the side of the gimbal.
3. Fix the camera on the gimbal with two M2 x L3mm countersunk screws.
   Determine the mounting direction of the camera on the gimbal by usage scenario (gimbal upward / downward mounting). Avoid squeezing the cable when installing the camera.
4. Connect the coaxial cable from the gimbal to the air unit and reinstall the cover back.

C-20S-ST
Take Walksnail Moonlight kit as an example:

1. Loosen the four screws on the back of the camera and remove the rear housing.
2. Use the crowbar in the package to disconnect the coaxial cable from the camera and remove the cable.
   The coaxial cable and its connectors are vulnerable. Please be careful when disconnecting and connecting the cable.
3. Insert the coaxial cable through the groove on the side of the gimbal.
4. Connect the coaxial cable on the camera. Fix the camera on the gimbal with four M1.4 x L5mm screws.

Installing analog camera

1. Connect analog camera cable on the camera.
2. Fix the camera and the camera mount on the gimbal with two M1.4 x L10mm screws.

Determine the mounting direction of the camera on the gimbal by usage scenario (gimbal upward / downward mounting).

Controlling the C-20S
The C-20S supports Headtracker direct / private protocol control, S.BUS / CRSF control, PWM control and MAVLink control, with the priority of the four control methods above decreasing in order.

• Headtracker Direct Control
  Please refer to Headtracker User Manual .
• Private Protocol Control
  Please refer to Gimbal Private Protocol .
• S.BUS / CRSF Control
  Connect the PWM1 in power-communication port to the S.BUS or CRSF_Tx of the receiver, which needs 3 channels to control gimbal mode, gimbal sensitivity and pitch respectively. Channel mapping can be done in the GimbalConfig software.
• PWM Control
  The PWM1~PWM3 are channels to control gimbal mode, gimbal sensitivity and gimbal pitch respectively.
• MAVLink Control
  Connect the UART_Rx and UART_Tx in power-communication port to the Tx and Rx in a certain serial port of the autopilot respectively, which needs 3 channels to control gimbal mode, gimbal sensitivity and pitch respectively. Channel mapping can be done in the GimbalConfig software.

Only ArduPilot firmware and PX4 firmware are supported currently. The MAVLink configuration are detailed in Appendix 2.

Gimbal Modes
There are five operating modes of the C-20S as below: FPV – Angle Control (FPVM-ANGL)

The input control value to the gimbal corresponds to its rotation angle. When the input control value is 0, the gimbal’s pitch axis follows the carrier’s movements with eliminating slight shaking.

• Horizon – Angle Control (HORI-ANGL)
  The input control value to the gimbal corresponds to its rotation angle. When the input control value is 0, the gimbal’s pitch axis remains horizontal.
• Horizon – Rate Control (HORI-RATE)
  The input control value to the gimbal corresponds to its rotation angular speed. When the input control value is 0, the gimbal’s pitch axis keeps current attitude.
• When controlling the gimbal via Headtracker, angle control modes must be used.
  For users employing the gimbal for non-head-tracking aerial filming, it is recommended to use rate control modes to achieve an optimal handling responsiveness.
• Return-to-Center (GOTO-ZERO)
  In this mode, the gimbal’s pitch axis maintains horizontal forward orientation. The gimbal becomes non-controllable in this state.
• OrthoView (LOOK-DOWN)
  In this mode, t the gimbal’s pitch axis maintains vertically downward orientation. The gimbal becomes non-controllable in this state.

Gimbal Sensitivity

The higher the sensitivity is, the quicker the response of the gimbal to follow the motion of the carrier, but the less it eliminates the carrier’s wobble.

The gimbal sensitivity is vaild only in FPV mode.

Carrier AHRS Fusion

When subjected to a large horizontal overload, the gimbal’s attitude algorithm may exhibit certain deviations, resulting in an inclined attitude. To rectify this deviation, it is necessary to transmit valid carrier AHRS data (carrier GNSS positioning needs to be effective) to the gimbal via the MAVLink protocol. Carrier AHRS fusion is available in all control methods.

Configuring, Calibrating & Firmware Upgrading
Configure the gimbal and upgrade firmware of the gimbal with the  GimbalConfig software.

Ensure the driver of the Config Module is installed on the computer before configuring, calibrating or upgrading.

1. Gimbal Presets
2. Channel Mapping
3. Regular Modes

Connect the Gimbal

1. Connect the gimbal upgrading port and the computer with the J1.0 Config Module. Power up the gimbal.
2. Run the GimbalConfig software. Select the COM port corresponding to the Config Module. Click “Start Debug” and confirm the software and the gimbal being connected.

The Config Module is sold separately. For some brands of dual Type-C cables, there may be cases where the computer cannot recognize the Config Module. Please try replacing it with a Type-A to Type-C cable.

Parameter Configuration Basic Operation

• After the gimbal is connected to the GimbalConfig software, the software
  will automatically download the parameter from the gimbal, or you can click “Download Param” to perform the download operation.
• Click “Save Param” to save the current displayed parameter as a local file. Click “Open Param” to read a locally saved parameter file.
• After selecting a new option in the drop-down box, the parameter will be automatically uploaded to the gimbal and take effect. After entering a new parameter in the parameter frame, press Enter key or click “Upload Param” to upload the parameter.
• After the parameter is uploaded, click “Save Param To Flash” to finalize it into the gimbal.

If not click “Save Param To Flash” after uploading parameters, the uploaded parameters will be lost when the gimbal loses power.

Regular Modes
Users can select three work modes from the gimbal’s various options to serve as their regular modes (M0 / M1 / M2).

Gimbal Presets

(Headtracker direct, S.BUS/CRSF & PWM control)

• The gimbal works in accordance with the preset values when there is no signal input or no mapped channel assigned. After the signal input is restored, the gimbal exits the preset state. The gimbal presets are invalid in MAVLink control.
• Preset gimbal mode: Users can choose one work mode from the regular modes (M0 / M1 / M2) as the preset mode.
• Preset gimbal sensitivity: setting range -1.0~1.0, with a resolution of 0.1.
• Preset roll, pitch and yaw angle: setting range -180° ~180° , with a resolution of 1° .
• The actual effective preset angles are based on the maximum rotation range of the gimbal.
• If you want to always use the preset values for some channels, map the corresponding channels to NULL.

Channel Mapping
(Headtracker direct, S.BUS/CRSF & MAVLink control)
Select the channels corresponding to gimbal mode, gimbal sensitivity, roll, pitch and yaw respectively. For Headtracker direct control (through datalink or Air Unit), all channels should be mapped to CH01.

• Mounting Type
  • The mounting type of the gimbal is AUTO by default, and the gimbal will automatically switch to DOWN/UP mode according to its attitude at power-on. The mounting type can also be manually set as DOWN or UP mode.
  • For tail-sitter VTOL aircrafts, it should place the fuselage in a level flight attitude and power up, or manually set the mounting type of the gimbal.
  • After the mounting type is set manually, make sure that the actual mounting type is consistent with the setting, otherwise the gimbal will enter the protection state.
• Tilt Protection (Pitch-lock & Horizon mode)
  • When the tilt of the mounting plane of the gimbal exceeds the protect angle, the gimbal will enter the protection state, at this time the gimbal will be neutralized and uncontrollable. When the tilt of the mounting plane is smaller than the protect angle, the gimbal will automatically exit the protection state. Tilt protection is effective in Pitch-lock mode and Horizon mode, not in FPV mode.
  • The protection angle can be modified according to the actual use. The setting range is 0° ~90° with a resolution of 1° . ≤ 15° means disabling the tilt protection.
  • After disabling the tilt protection, the gimbal may work abnormally when the attitude angle of the carrier is large.
• Parameter Tuning
  For cameras with larger moment of inertia, mounting them on the gimbal may result in gimbal shaking. In such cases, increasing the gain value can enhance stabilization effects.
  It is strongly recommended to use the default gain parameters if unnecessary.
• Pitch Calibration
  In FPV mode, the gimbal’s pitch center may exhibit a slight deviation. This parameter allows fine-tuning of the pitch zero point specifically for FPV mode. The adjustable range is -10° ~+10° with a resolution of 0.1° .
• Calibrating & Firmware Upgrading
  If the attitude of the gimbal tilts or drifting slowing when no control signal input, it is necessary to calibrate the gimbal.

1. To calibrate the gimbal. Keep the gimbal static. Click “Gyro Calibration” and wait for the calibration to complete.
2. To upgrade the firmware. Click “Open Firmware”. Select the firmware file. Click “Start Upgrade” and wait for the upgrade to complete.

Appendix 1 Supported Cameras

O3 Version	DJI O3 Air Unit
Standard Version	Walksnail Moonlight Kit
	Walksnail Avatar HD Kit V2 (Dual Antannas Version)
	Walksnail Avatar HD Pro Kit (Dual Antannas Version)
	Walksnail Avatar HD Pro Kit
	Walksnail Avatar HD Kit V2
	CADDXFPV Polar Starlight Vista Kit
	CADDXFPV Nebula Pro Vista Kit
	RunCam Link Phoenix HD Kit
	RunCam Link Wasp Kit
	RunCam Link Night Eagle Kit

Appendix 2 MAVLink Configuration

ArduPilot 

Serial port number can be changed according to the actual situation.

SERIAL1
SERIAL1_BAUD	115
SERIAL1_OPTIONS	1024
SERIAL1_PROTOCOL	2
SR1
SR1_ADSB	0 Hz
SR1_EXIT_STAT	0 Hz
SR1_EXTRA1	0 Hz
SR1_EXTRA2	0 Hz
SR1_EXTRA3	0 Hz
SR1_PARAMS	0 Hz
SR1_POSITION	0 Hz
SR1_RAW_CTRL	0 Hz
SR1_RAW_SENS	0 Hz
SR1_RC_CHAN	0 Hz

PX4

MAVLink
MAV_1_CONFIG	TELEM2
MAV_1_MODE	Custom / Gimbal
MAV_1_RATE	115200 B/s
Serial
SER_TEL2_BAUD	115200 8N1

The MAV_1_MODE is recommended as Custom.

Documents / Resources

RoboT C-20S Single Axis FPV Gimbal [pdf] User Manual C-20S-O3, C-20S-ST, C-20S Single Axis FPV Gimbal, C-20S, Single Axis FPV Gimbal, Axis FPV Gimbal, FPV Gimbal

References

• User Manual