Diagnosing FC power/boot issues

Red/Blue/Green LEDs light up/blink normal when FC booting,  but FC can’t be connected to configurator, or can’t go into DFU.

  • Intall DFU and STM VCP drivers, Click Installing Betaflight/INAV for details
  • Unplug USB and close configurator,  replug USB and run configurator again.
  • Try other USB cables
  • Check if there is dry joint on USB connector pins

Red LED(3v3 indicator) doesn’t light up

  • After plugging USB
    • Disconnect USB, then test the continuity between 3v3 and G, 4v5 and G
    • If there is continuity between 3v3 and G
      • Double check if there is solder ball/splash on the capacitors/MCU pins
      • Desolder/Disconnect all devices from FC board, test it again.
    • If there is continuity between 4v5 and G
      • Desolder/Disconnect all devices from FC 4v5 rail, test it again.
    • If no continuity
      • Try another USB cable
      • Check if there is dry joint on USB pins
  • After plugging battery
    • Disconnect battery, then test the continuity between 5V and G,  4v5 and G, 3v3 and G
    • If there is continuity between 3v3 and G
      • Double check if there is solder ball/splash on the capacitors/MCU pins
      • Desolder/Disconnect all devices from FC board, test it again.
    • If there is continuity between 4v5 and G
      • Desolder/Disconnect all devices from FC 4v5 rail, test it again.
    • If there is continuity between 5V and G
      • Desolder/Disconnect all devices from FC 5V rail, test it again.
    • If no continuity
      • Test the voltage between 5V and G, 4v5 and G with battery connected
      • Check battery connector(XT60)
  • Pls shot a few high resolution and focused photos of FC still installed and wired,  then you can take it apart.  These photos will be a huge help for diagnosing if you decide to email us for service.

FC hang when booting

  • Double check if FC is flashed with right Target
  • If FC can’t boot normal with I2C devices connected
    • check I2C devices wiring(SCL-SCL, SDA-SDA),  and check if I2C devices are powered on when FC initialization.
    • Try desoldering/disconnecting I2C devices from FC board to see if FC can boot normal.
    • Reflash FC with full chip erase selected,  CLI “defaults” after reflashing, then reconfigure I2C devices in configurator.
    • or set I2C speed in INAV configurator
      • Some I2C sensors are reported to work unreliably on default 400kHz speed. INav allows to reduce I2C clock rate to 200kHz and 100kHz to allow these picky sensors to function properly.
      • If compass sensor is not recognized or hangs when setting, please try CLI command “set i2c_speed = 200KHZ”  before reporting a bug.

Red LED lights up, Blue and Green LED blink alternately three times

  • Gyro/Acc can’t be detected when FC initialization.
  • Check if FC is flashed with right Target
  • Check if there is solder ball/splash on Gyro chip, or solder ball/splash on capacitors nearby Gyro

MCU heat fast after powering

  • If F7/F4 chip heat fast after powering,  and finger can’t touch MCU surface for more than 1 second,  Mostly like MCU is dead, there is short circuit in core of MCU.
  • sometimes it is caused by spikes on ESC signal rail when motor is blocked,  result in short circuit between MCU S1/S2/S3/S4.. pins and ground.

Servos don’t work with INAV firmware

  • Be sure INav firmware version is compatible with configuration version,  e.g. use configurator 2.2 for FW_2.2.x
  • Enable  motor and servo output in “configuration” tab.
  • Configure servo mixer in “Mixer” tab.
  • Disable “External PWM servo driver”
  • WING series FC
    • Test the voltage between “Vx” and G when FC is powered via battery.
      • If no voltage on Vx rail, disconnect/desolder all servos from Vx rail, test it again.
  • Other series
    • Test the voltage on servos power source, e.g. 5V

GPS doesn’t work

  • Red GPS icon at top of configurator
    • Check GPS wiring, GPS TX – FC RX, GPS RX – FC TX
    • Check if GPS is configured on proper Uart
    • Check GPS protocol in configuration tab, usually use UBLOX protocol for most of GPS modules
  • Blue GPS icon at top of configurator, no satellites signal
    • Put GPS nearby windows or outside
    • Check if GPS is interfered by HD cameras, try turning off HD camera before GPS fix.
    • Connect GPS to USB-TTL module, use U-center to revert GPS to default configuration,  then check the GPS status in u-center.