APM, no heartbeat UART0 probably broken

I was just playing with my apm 2.0 and minimOSD and everything was just working fine, then suddenly all out of nothing I stopped to get "heartbeat packet" so the minimOSD could not get messages from APM 2.0, then I tried to connect APM to mission planner but with no luck. then I to my ohm meter and started to measure an I found out that there was only 2.3 ohms from GND to RX0 on UART0, just to be sure, can anyone measure the resistanse on their board between RX on UART0 and GND (I am pretty sure it should be reading something high but not so close to zero)

see picture to know where to measure if you don't know it already :)

thanks in advance!!! :)

explain.PNG

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  • 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

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