Cannot Update firmware to APM via Mission Planner 1.3.5

I currently have a APM 2.5 from 3dr and have not had any problems updating firmware via Mission Planner until now. When I tried to upload Arducopter 3.1.5 via USB over the weekend it gets through the board version check and then downloads the hex file and then goes through reading hex then fails with a “Communication Error”. The interesting thing is that I also use APM Planner 2 and was able to upload via APM Planner 2 without any problem. Much faster that it ever was when I was using Mission Planner. A while ago I saw a post to DIYDrones talking about Mission Planner checking the PIX Hawk boards for a valid id that would tie them back to 3DR. I don’t know why this would be a problem because this is a valid 3DR board and does finalize the board version check but I wonder if there is something in this code that may have started to affect what happens with the APM 2.5 even though this is a valid board not 3rd Party board. Any info on this would be great as I don’t have the funds to upgrade yet even though I would like to.

check your usb cable. it most likely a connection issue

I know it is not a usb problem because I am using the exact same cable and connection when I open APM Planner 2 and succeed with the firmware update. I then go right back to Mission Planner to re-attempt a firmware update and the update fails again in the exact same way. This is a software problem… Before the last update to Mission Planner or maybe before the last 2 updates not sure I was able to use the same cable and update the firmware. This problem seemed to arrive with the update where people started complaining about the third party pixhawk boards not being supported in Mission Planner anymore. The odd thing is that my board is a OEM 3DR APM 2.5. I guess I have a unique problem because I don’t see this problem with very many other APM owners but there are a few.

I do believe I found a work around for this problem in Mission Planner which was a recommendation from another user. I have other serial com interfaces on both my PCs that I used to try and update the firmware. One of these serial interfaces connects my 3DR Radio. I when through the list in Device Manager and disabled all but the Arduino interface. After I did this and Mission Planner did not have a problem uploading the firmware. I went back and enabled all the serial interfaces except for the one connecting the 3DR Radio just to see if this one was causing the problem and it failed again. I do believe there is a bug in Mission Planner and how it chooses the com port even thought I manually chose the right com interface before attempting the upload. There is some confusion in this. I also think this is why APM Planner 2 works because they have a connection wizard to only consider the connections I manually build.

MP version 1.3.16

I can confirm I had this same problem today. Couldn’t upload a new firmware, getting “connection error”. USB cable was not the problem.

Disabling the other two COM ports in Windows Device Manager, and re-trying, uploaded and verified the new firmware fine.

A bug with MP.