[chbot] ATSAMD21 programmer

[Mark Atherton]

Just compiled an Arduino LoRaWAN demo sketch, and programmed it into a 
SparkFun SAMD21 Pro RF.

Post programming, the blue LED appears to be on (or flashing fast), and 
the Arduino IDE is no longer able to find/program the unit.

Win7 Device Manager reports the USB device under 'Other devices' 
"Sparkfun SAMD21 Pro RF" with a VID of 1B4F, and PID 214F there is also 
a yellow exclamation point indicating that the associated USB drivers 
have not been installed.

A search of the web indicates that the bootloader has been corrupted, 
but I am surprised that the hardware can still enumerate a USB device - 
mind you, I know nothing about this processor.

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So the short-and-sweet question: anyone seen/fixed this issue before, it 
seems like a popular way of bricking these (expensive) boards.

I have found the bootloader hex/binary, and fetched a copy of Atmel 
Studio (870MB), just need to find a cheap, readily available, and 
compatible programmer.

Comments please.

Regards, Mark