Conflicting external compass <-> OLED Display 1306?

Having problems with the external compass I finally found how to reproduce my problem:
when the OLED is active (NTF_DISPLAY_TYPE 1) the external compass is not discovered (only one COMPASS_DEV_ID).
When I disable the OLED by setting NTF_DISPLAY_TYPE to 0 and then powercycle the board, the external compass is also discovered and functional.
Tried this wit the 3.6 RC7, RC8 with the normal and the chibiOS Version.

Am I missing something to get both working or did I just stumble across a bug?

Board is a PX4V3 (Drotek DROPIX), setup is Quad as V-Tail.

Did the OLED display work on a previous Arducopter version?
Check on the rear of the OLED board and see if there’s a jumper or solder pads to change the address so it doesnt conflict with the compass.

Hi Shawn,

Thank you for your reply.
I tried several things, also the stable 3.5 version, the solder jumper on the back of the OLED PCB ,…
The only constant seems to be: setting NTF_DISPLAY_TYPE to 1 results in the display is on and the external compass is not detected. When set to 0 the display is off and the compass detected and functional. It is also indepent whether the OLED is plugged or not!
As I digged a little I found that the address of the OLED seems hardcoded in Display_Backend.h by a #define NOTIFY_DISPLAY_I2C_ADDR 0x3C. So I tried it with a version i compiled on the actulac code but with the address set to 0x3D (solder jumper on the back was changed what results in address 0x3d. But same effect as above. OLED not funtional as NTF_DISPLAY_TYPE is set to 1, also when the dispay isn’t connected at all. Strange …

In the meantime I’ve got frsky telemetry transmission to my taranis display working. Some kind of “workaround” :wink:

supplementary info: I did’t try another GPS/Compass with an other onboard compass chip because I didn’t have a free one here. I’m sure that would have been a solution, too.