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Topic: Replacing 32u4 on any Arduino YUN? (Read 179 times) previous topic - next topic


Mar 26, 2021, 06:50 am Last Edit: Mar 26, 2021, 06:52 am by WhidbeyBill
I've managed to compromise several Yun boards by accidentally applying 5v to 32u4 digital pins when the device wasn't powered. Sketches load and do some things but some functions don't work, ALU for instance?. Thinking about replacing the 32u4's and wonder if the bootloader supplied by the factory is sufficient to load sketches right out of the box, so to speak. I am not a proficient coder but can write sketches. The Yun's are a spare Rev0 (originals) and a REV1 (Doghunter .org boards) . Comments? for $6 I can salvage the Yun.
I notice that Facchinm <https://github.com/arduino/yun-go-updater>
yun-go-updater does a bootloader refresh.  I can vouch that the yun-go-updater works on all three versions I have, but won't restore the functions even when reflashing the firmware. Thanks.


You shouldn't need any bootloader on the replacement '32U4. Once you replace the chip, if you use the network interface to load your first sketch, it will automatically put the bootloader back for you.

Either use the Arduino IDE and select the Yun's network port (not the USB serial port) to upload the sketch; OR, use a web browser to connect to the Yun's configuration interface, and choose the upload sketch option on one of the initial pages. Either way, the Linux side of the Yun takes your sketch image, combines it with a fresh copy of the bootloader, and uses a SPI style connection to the '32U4 ICSP connection to load the combined bootloader and sketch.

Once you've loaded your first sketch this way, you should be back to normal.


Apr 02, 2021, 09:37 pm Last Edit: Apr 02, 2021, 11:32 pm by WhidbeyBill
Hi there, Thank you for the TIP in your response. I suspected as much, since the Factory Part (bought at DigiKey) seems prepared for what I want to do. I believe at this point I may have only damaged the port (pin) that had 5V on it but I just got the parts and haven't started the removal and replacement. If this works as expected I won't have a worn out hobby board.  The older boards at least have the layout for the easier replacement using the AUR part-44TQFP. I am really pleased with my Original Yuns. Had one in continuous service for over five years in a monitor and I download yesterday's water plant log daily. Good to hear from you "ShapeShifter" BTW we still have the bootup pause implemented in rc.local running in my sketch. Pity it doesn't run in Rev2. I have considered soldering in a 10K resistor to the 9331 end of LED0_WLAN_R12  pull-up resistor on the Rev2 Board and wiring that to an unused digital pin on the 32u4. That would provide a ready signal for the Setup 'while' statement when the AR9331 is pretty much finished a boot.

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