Just got it from Chinese forum and translate roughly
Regarding White LED flash
White LED is the signal of IMU status, which has nothing to do with firmware version. So using new firmware won’t cause more/less appearance of white LED.
Logic meaning of white LED flash:
1. Error value between GPS data and IMU computing, which happens when: A, GPS signal unstable. Sometimes get adequate satellites with low reliability, which differs too much from the IMU computing. B. Fierce movement during flight makes the sensor in IMU out of working range, the computing result of IMU is different to GPS data. C. Vibration causes noise to IMU.
2. Error value between Compass data and IMU computing, which happens when: A. Compass not calibrated correctly. B. External interference to compass after successful calibration. B. Fierce movement during flight makes the sensor in IMU out of working range, the computing result of IMU is different to GPS data. C. Vibration causes noise to IMU.
3. Error value between barometer and IMU computing, which happens on crafts with high vibration.
Solution:
1. Intermittent white LED is no problem, especially when doing fierce movements. Hold the position for a while and the white flash would be off.
2. When searching GPS (3 red flash to 1 or none), it is normal to have white LED flash, even the craft is on the ground. If everything ok, the flash should stop soon.
3. In some cases, even though GPS is adequate (no red flash or just 1 red flash),but it’s not reliable, and the LED might flash in white. If the craft is still on the ground, pls fly carefully as it may not hold position in GPS mode, drifting/hunting, showing severe attitude correction of the craft. Pls do not fly in GPS mode in this case. What’s more, the GPS signal strength varies from time to time even on the same spot.
4. If white flashes happens when you yaw, even very slowly, pls recalibrate the Compass. Pls be noted that it is not necessary to calibrate at every new flying area unless components is added/removed, or mounting location changed no matter they are electric or mechanical. Since multirotor is a highly integrated system with different components, pls make sure the GPS/Compass is far from noises, interference, electronics or wires with high ampere.
5. Vibration will cause white LED flashing, too. The high frequency vibration might be result from unbalanced motor or props. So pls check all mechanical connection, and balance on motors and props.
The above is the reason and solution on white LED flash. Intermittent flash is normal, which won’t matter during flight. For continuous and frequent flash, pls check your craft according to the above and fly carefully.
