3D Robotics

Update on ArduPilot Mega reset button issue

Jordi and the team have diagnosed the issue users are having with the reset button on the ArduPilot Mega IMU shield not working. Here's what we've found:

1) This is due to a conflict with the FTDI chip when the USB cable is plugged in. It is not an issue in the field, when the board is powered the normal way, with the ESC.

2) If this troubles you, we will be releasing instructions on how to modify the board (cutting a trace and soldering a wire jumper) to avoid it. The next batch of boards will have this fixed. 

3) Needless to say, if your IMU shield is on the bottom and you're using the reset button on the APM board, there is no problem.

4) Remember that when you upload code to APM, Arduino automatically resets the board, so no manual reset is required. So you shouldn't have to use this button in normal operations anyway.

You need to be a member of diydrones to add comments!

Join diydrones

Email me when people reply –


  • I am following the ArduRover2Setup instructions to load the ArduRover code and was successfully able to soft reset the APM using the CLI.  I however have been unable to perform the subsequent hard rest of the APM using the reset switch as recommended.

    May I assume that item 4) above means that performing a soft reset on the APM should be enough to successfully upload the ArduRover code to the APM.?

  • Admin

    I made the capacitor to resistor swap on my IMU Mega Foxtrap version, but it still did not cure the reset problem with the USB cable connected. It would be nice to have access to the IMU Mega Hotel version Eagle board and schematic files.



  • I believe I am having the same problem. I want to do a little further investigation first. I did notice that if I power up the APM/IMU with the slider switch away from the DIP switches, it attempts to read flight data but still disconnects.

    I read somewhere you can do everything in the CLI that you can do in the configurator. Where do you set PIDs in the CLI?

  • BTW - What was the fix applied to the rev H board? Replacing the capacitor with a 1K resistor as shown below? Something else?

    Still no good explanation for this behavior.............
  • I'm using some modified code, so it does not matter what position the slider switch is in. I'm positive the issue is the board is not being released from the reset state. If the reset state is released, it will connect. It is just more often than not, the board stays stuck in the reset state. The 1st few lines of code in the setup routines have been modified to turn on an LED. If the LED turns on, indicating the board is running, it will connect.. If the LED stays off, it won't connect.

    This problem only exists with the configurator. Using standard ArduCopter code and it's configurator, AeroQuad code and it's configurator, or my modifed code with the AeroQuad configurator. All behave the same way. And all work as expected with the Arduino serial monitor.

    I need to get a scope out, but I'm beginning to wonder if the DTR signal timing is different on the Arduno serial monitor vs the configurators?

  • Any update on this? I'd love to make the little fix so the button works reliably.

  • Admin

    The reset button works fine on my IMU Mega when I am using the IMU Mega USB port. I can reset the ArduPilot Mega anytime even when connected to the USB port.

  • Ahh good to know. Thanks for clearing this up. I had noticed it, but it wasn't high on my priority list to deal with.

    I'll be curious to see the fix when its posted.

This reply was deleted.