APM 2.0 No longer xmt data on USB

APM 2.0 + MinimOSD, everything is working great

During a video system upgrade I accidentally applied 12vDC to the MinimOSD while the 5vDC solder jumpers were installed.

Since then I can't establish a serial connection to the APM over the USB port.

MinimOSD appears to be dead,  I haven't really looked at it much.

APM 2.0  shows up as ATMega when I attach the USB port

MinimOSD was connect to UART0/2

Arduino IDE can't connect to ATMega

Data from PC -> ATMega appears to be working (the LED flashes)

Data from ATMega -> PC does not work (no LED flashing)

Something must be going between the two because the USB does get properly labelled when connected.

AVR mkII works over the ISP and I downloaded the Adruino bootloader.

I think I blew the automux.  Is there a way I can bypass the automux and get the serial port working again?

I need to be able to download new arducopter firmware & configure it using mission planner.

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  • Looking at the schematic  USB3 (D+) & USB2 (D-) connect to 29 (D+) & 30(D-) on the ATMEGA8U2-MU.  Is that the automux?

    I'll try to reflash the ATMEGA8U2 via the SPI_PPM interface later today, maybe that will help.

  • Hi,

    I think I blew the automux.  Is there a way I can bypass the automux and get the serial port working again?

    I think the same.

    There are some solder jumpers to connect the telemetry port to either UART0, UART2 or MUX. Default is MUX. You could re-jumper to UART0 and use an external USB serial adapter connected to telemetry port and it should be OK - BUT for firmware upgrade you have to start the bootloader manually by pressing RESET just before trying upload. (default is that one of the control flow or handshake signals from the USB/ATMegau8 resets. That's why the APM seems to reset just because you open a serial connection via the USB. It really does reset).

    Alternatively, remove the mux IC and connect the pins together that the IC used to connect together when USB was used (see schematic). Or replace the IC :)

    Regards

    Soren

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