BLITZ Wing H743 — MAX7456 OSD text OK but no camera passthrough (grey screen)

ArduPlane Plane 4.7
1

Hi,

I’m struggling with camera video passthrough on my iFlight BLITZ Wing H743 (hwdef: BlitzWingH743, firmware 4.7.1 stable). I can see the OSD telemetry overlay fine, but the video feed itself is a uniform grey background.

This was working correctly before, and started right after a firmware reflash — no hardware was touched in between.

Troubleshooting so far:

  • Camera wired directly to my VTX (bypassing the FC): works fine
  • Tried a second, different camera through the FC: same grey screen
  • Confirmed camera outputs a genuine active video signal via multimeter (voltage fluctuates when covering the lens)
  • OSD_TYPE=1, OSD_OPTIONS=1, both at documented defaults

Since two different cameras show the identical symptom, and the FC is brand-new, it seems unlikely to be a one-off hardware defect and more like something systematic in the firmware/hwdef for this board.

I came across the Betaflight fix for IFLIGHT_H743_AIO (PR #10869) — a MAX7456 SPI clock speed misconfiguration causing it to run at 50MHz instead of the correct divider. Could ArduPilot’s BlitzWingH743 hwdef have a similar issue? Is there a way to check/override the SPI speed for the OSD chip?

Do you have any other suggestions of what I could have missed or done wrong ?

Thanks in advance

2

There is a camera switch, which camera input are you using?

3

Hi and thanks for the reply,

I am using VI1. I tried to act on relay 3 via Mission Planner but it is not available. I tried to affect it to GPIO82, but it did nothing except preventing to arm (pre arm checks failed). The only relay available by default is relay 2 and changing it did not change anything for me.

Is there an other switch I would have missed ?

4

Found the root cause, and I believe it’s a documentation/hwdef mismatch bug:

This matches an existing report: Blitz H743 wing — Vi1 doesn’t work, Vi2 does, and the GPIO82/RELAY3 software switch between them doesn’t work either.

I checked the fix that was merged for this (PR #28185: AP_HAL_ChibiOS: add camera switch to iFlight Blitz H743 Pro by andyp1per · Pull Request #28185 · ArduPilot/ardupilot · GitHub , merged 2025-01-25). Looking at the diff, it only added the actual pin definition to BlitzH743Pro/hwdef.dat:

PD11  CAM_SW OUTPUT GPIO(82) HIGH
define RELAY3_PIN_DEFAULT 82

For BlitzWingH743, only the README.md was updated to describe the same “Camera Switch” feature — but the corresponding hwdef.dat change was never made for the Wing. So the public docs (ardupilot.org) claim GPIO82/RELAY3 is available on the Wing, but the firmware itself has no such pin defined — which is why setting RELAY3_PIN=82 on my board returns an invalid-pin error (and broke arming when I tried).

Could someone confirm and port the same two hwdef.dat lines from BlitzH743Pro to BlitzWingH743? Seems like a trivial fix once flagged.

I have wired my camera directly to VI2 as a hardware workaround : working !

Thanks!