Help with iNav + Omni F4 V5 + GPS - Where to put Magnitomiter SDA/SCL?

Just getting into this and am trying to convert my son’s Storm 240x racing drone that came with a CC3D FC to one that can support simple RTH so that he (well we!) can play a little more adventurously. Swapped the FC to an Omnibus F4V5, upgraded the Rx to 7 chan to get a RTH switch & installed iNav FW. Got it all working with the SBUS Rx on UART6. Added a M8N GPS on TX3/RX3 and got it working but I’m not sure where the SDA/SCL from the GPS mag goes as these connections seem to be on the same TX3/RX3 pins. I tried shifting the GPS to TX1/RX1 pins but iNav just rejects the selection of GPS as sensor on UART1 after reboot. Any idea what I am doing wrong? Is UART1 being used by another function?

The pre-arm compass calibrated light is green. Does this mean that the board has its own compass and perhaps I don’t need the GPS one for the basic RTH I need?


Read the internet again and spotted this thread

Looks like the problem was that I had MSP still set on UART1. Switched MSP off, put the magnetometer into the SDA/SCL pins and it looks like its all working now.

Just wished I spotted the advice to calibrate the accelerometers before the board is wired up though…


Hi Richard

I have the same FC and although the GPS works fine the Magnetometer / Compass does not work, it is greyed out in Betaflight, I have the SDA/SCL wires connected to the right pins (see diagram) and have set TX3 and RX3 as IC2 resources.

Could you send me you GET MAG settings from your CLI so I can compare your Mag settings with mine by any chance?

Many thanks.

CLI output below.


get mag

align_mag = CW270
Allowed values: DEFAULT, CW0, CW90, CW180, CW270, CW0FLIP, CW90FLIP, CW180FLIP, CW270FLIP

mag_hardware = HMC5883
Allowed values: NONE, AUTO, HMC5883, AK8975, GPSMAG, MAG3110, AK8963, IST8310, QMC5883, MPU9250, FAKE

mag_declination = 0
Allowed range: -18000 - 18000

magzero_x = -90
Allowed range: -32768 - 32767

magzero_y = -206
Allowed range: -32768 - 32767

magzero_z = 39
Allowed range: -32768 - 32767

mag_calibration_time = 30
Allowed range: 30 - 120

imu_dcm_kp_mag = 10000
Allowed range: 0 - 65535

imu_dcm_ki_mag = 0
Allowed range: 0 - 65535

inav_auto_mag_decl = ON
Allowed values: OFF, ON

Hi, if you connect your GPS like this, can you use also a Frsky XSR smartport like showed in this blog?
New to this, just trying to use GPS and smartport. Any help is welcome! Using F4 Omnibus V5.1. Thanks, Chris