In the firmware download section, I have pushed a new firmware update to allow the use of an external compass on the VRBRAIN 4.0 or 4.5
The instructions on how to connect an external compass can be found here: Using an Eternal Compass
Be aware that you cannot connect an External compass without cutting a trace or disassembling the internal chip if you fly OCTO or OCTO_QUAD.
Because the secondary I2C port is shared with output 7 and 8, you will also loose Gimbal Control if you fly Hexa or Y6.
Please feel free to ask any questions if something is not totally clear.
Have fun and Fly safe!
The VirtualRobotix Team