We’ve recently encountered an issue with Walksnail VTX units not displaying the OSD properly or flickering when paired with some SpeedyBee flight controllers. This post aims to detail the problem, possible causes, and potential fixes.
The Problem
Many users report the following:
- OSD Flickering: The OSD rapidly flashes but the video feed remains stable.
- OSD Not Displaying: In some cases, the OSD doesn’t show up at all.
The issue is particularly noticeable on SpeedyBee flight controllers, with reports from various models, including the F405 Wing. Walksnail VTX units function normally when tested on other brands of flight controllers.
Key Findings
- Microcontroller Compatibility:
- Flight controllers using AT32 MCUs seem more prone to flickering or OSD failures due to weaker internal pull-down resistors.
- Controllers with STM32 MCUs are less affected.
- Grounding Issues:
- Using a common ground other than the one provided on the SpeedyBee digital VTX port can cause the OSD to disappear completely.
- Firmware and Settings:
- Incorrect INAV or Walksnail firmware/settings can also exacerbate issues.
Manufacturer’s Statement
According to Walksnail support:
“The VTX is not inherently faulty. Flickering OSD typically points to flight controller issues. Replacing the SpeedyBee controller with another model can resolve the problem.”
This suggests that the problem lies with the SpeedyBee hardware design rather than the Walksnail VTX.
Suggested Fixes
- Pull-Down Resistor: Adding a pull-down resistor on the UART line connected to the Walksnail VTX may stabilize the OSD. This workaround is recommended for AT32-based controllers.
- Firmware Updates:
- Update INAV and Walksnail firmware to the latest versions.
- Ensure fonts and OSD settings in INAV are properly configured.
- Testing on Alternative Controllers:
- Try the VTX on another flight controller to rule out hardware issues.
- If the OSD works on other brands, consider replacing the SpeedyBee FC.
Example Setup
