Replies to This Discussion

Permalink Reply by Søren Kuula on December 12, 2012 at 11:33am

Hi,

In the schematic and also on an APM2.0 board I have, the UART0 rx and tx pins from the connector on your picture both go through a 1.0 kOhm resistor before continuing to the muxer (the TS5A23157 chip). Damn, I also see and measure now that they go directly to the ATMega2560 pins 2 and 3.

I have several megaohms there.

I would probably try to lift pins 2 and 3 on the 2560 off the board (some fine tools and skills are needed). Does it no longer have 0 ohms? Then the ATMega2560 has had an input welded to ground.

Regards

Soren

• ▶ Reply

Permalink Reply by Bjarni on December 12, 2012 at 3:07pm

Thanks very much for your reply :)

I did think this just the same way as you, I have lifted pin 2 on ATMega2560 and when I measure just the pin 2 resistance to ground I get 2 ohm so it seems obvious that the RX on UART0 is broken/faulty so I can not use it any more, but do you know if there is a psossible solution to this? I was thinking if I could use UART0 instead of UART2 to communicate with the APM, I know that the arduino bootloader uses UART0 to download new program to the APM, but I was just thinking that I could have mavlink communications on UART2 to connect to mission planner, what do you think? if I need new firmware on the arduino I can propably download it straight through the programming header/ICP (In circuit serial programming)

please tell me if you see any possibility in this or any other solution so I can connect apm to mission planner :)

best regards

• ▶ Reply

Permalink Reply by Søren Kuula on December 12, 2012 at 4:49pm

Hi, I can only think of replacing the atmega or the whole apm2. Replacing the atmega will not cost you much. You will need an isp programmer to flash a bootloader in the new one. Of course you can also use one to flash a build of the firmware with UART2 support into the old one... still I would not recommend to fly with partially defective hardware. Replace the atmega...
Regards, Soren

• ▶ Reply

Permalink Reply by Bjarni on January 28, 2013 at 10:27am

Hi, I just wanted to tell you that I replaced the atmega2560 :) and it works now and I am damn proud of myself to be able to replace this chip ;) I used small baking oven to heat the solder up and then I could "peel" it off with tweezers.. the most problem was to solder it back in place because I had some solder bridges, but after some time with the solder wick I was able to remove the solder bridges and now everything is working like new :D

• ▶ Reply