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By gcl8a
#188909
I have one of the SAMD21 Mini breakout boards — about a month old — and I can’t get it into bootloader mode. I know the “double tap” trick, which I’ve used in the past successfully, but it won’t work this time.

More details:

I’m using the chip for a UGV code, and it has been working very well for that: I2C, UARTs, interrupts, Kalman filter, etc., etc., all running pretty fast. However, it most every time I plug the chip in after I haven’t been using it for a while, it doesn’t show up in the Ports menu in the Arduino IDE. Until now, double tapping the reset button has always put it into bootloader mode, after which I could program it normally and it worked. But now it just won’t do it. When I double tap, there is the faintest flicker of the yellow LED, but then it stays off, and the chip doesn’t show up.

I have completely disconnected it from my circuit, and I have tried two different USB cables. I have also tried restarting the IDE, even though that shouldn’t affect the double tap. The last code on it was working fine — it ran for "quite a while" without fail, and I was able to upload normally during my last session (after double tapping at the start).

What is the easiest way to reset it? I don't have an external programmer, but I could get one, if that is what it takes.
By Leandro
#192026
I had the same problem.
Eventually solved it by burning again the bootloader via an ATMEL programmer using the EDBG interface in the Arduino IDE.
I tried to do it via the ATMEL studio but it kept complaining about "Unexpected Chip Identifier 0x10010205 (expected 0x1001000a)."

Leandro