I'm using Planner 1.1.14 with a new APM2 board. Win XPpro and the Atmega2560 inf driver file from the repository.

Planner loads and verifies the 2.27 firmware but it does not connect to the APM2.  I have used Putty and it does reset the APM2 on connect and I do see packets with mixed binary/alpha content (presumably MavLink).

When watching the APM2 board, it does not appear to come out of reset after Planner opens the port.  Since the reset step works correctly with Putty, it seems as though Planner is holding the reset line for some reason.

Should I add this as an "issue" ?


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Hi there

I have the same issues but the writed fixes here will not work.


I can update the APM 2 to Hexa X V 2.4 and i wait 5min until i connect but every time the same:

Mavlink Bad Packet (crc fail) len 0 crc 65535 pkno 0


I also updated to the newest APM Planner: 1.1.38


Does anyone has a working fix ? I think that is not a little problem, many of us has the same problem. It has now about 10 threads with this problem. 


So please, if anyone have a fix for it post it with a short manual if we that need.


maaaaaaaaany thx from switzerland



Tino: This thread is old and most of the issues here have been addressed long ago. I can't verify your problem myself -- all boards here are currently working fine with the latest code. So this must be something particular about your setup. 

You'll have to give more more info to diagnose: 

--USB or Xbee?

--Please open up the serial monitor (check box in the MP help screen) and see what it says when it's failing.

--Can you access the APM 2 board via the CLI in the MP Terminal?

Hi Mr Anderson

Thx for your reply


1. Im using USB connection (X Bee only connected to APM)


2. Serial Monitor will say:

MAV Link readpacket read error: Timeout 

Mavlink Bad Packet (crc fail) len 0 crc 65535 pkno 0 

and the last parameters:

 Mav Data: Len 0 btr 0

4 Start

Not a 1200

Valid eeprom contents 


3. Im not can access to APM via Terminal. If i hit 3 times enter it makes nothing. 



Did you have any idea ? 

I'd start with trying a different USB cable and PC--load the firmware again with that. You don't appear to have any connection to the board at all on this one. 


Ive try now to connect to terminal 20 times and now im in ;-) i have connection to it but only the terminal :-(

I dont think that is an issue from the cable or PC.... 


Edit: In the terminal i see that i can not calibrate the gyros. Also the will not initialize if i go into test mode.....


I have reload now the code and i see that the APM Planner will say after flashing the firmware "done". But if i look on the serial monitor it stops on " Init gyro"


Is that normal ?


Sorry for that many question. I have waiting a long time for the APM 2 and now it dont work :-( 

You may have a defective board. I can't verify any problems on any of the APM 2 boards here. Please contact sales@3drobotics.com and get a RMA.


How about taking a stab at this one-



I am having similar problems. Perhaps I should do the same.

My APM2 also can't connect using USB. It can update firmware fine though.

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