I cannot upload to Seeed Studio XIAO SAMD21. I have fixed this problem before with the reset steps… but now both the green and yellow LED are always on. What does this mean and how do I fix?
Green LED is the power indicator.
Two quick resets will cause Yellow LED to flash slowly, but if you are not quick enough, Yellow may remain on.
yellow should fade when in upload mode… try double clicking the reset button
also lower your serial speed to 19200 or 9600 in future sketches to make uploading easier
Double-click the reset button quickly.
The green LED should start pulsing if the board successfully enters bootloader mode.
Once in bootloader mode, try uploading your sketch again.
not the green but the amber led is the one that fades in and out
I am Lightning McQueen fast over here. Anyway, the yellow LED Automatically turns on when I plug the board in. When I am trying to enter boot loader mode, it kind of flash dims a little idk. I can’t get it to enter bootloader mode (I have done that many many times in the past).
I dont think the Yellow LED comes on automaticly… it has to be programmed to be on
When in bootloader Mode the anber LED starts “breathing”
do you have one of these?
No I have this Getting Started with Seeed Studio XIAO SAMD21 | Seeed Studio Wiki
And it shouldn’t and I cannot upload to the board nor enter boot loading.
you did the short the wire procedure? That device has a reset button and will also help recover a bricked device… what was the last program you uploaded?
I was never able to upload a program 
the port was closed when first tried to upload. I will try to hit the reset button. I did try the short-wire procedure.
check and make sure your USB cabe is data and power and not data only… try another usb cable and port
cable should be good I am able to upload to another one of the same boards just fine.
If you cannot enter bootloader mode after a correct reset, the bootloader may have been corrupted. The following links may be helpful.
‘How to unbrick a dead XIAO using a XIAO(DAPLink) and OpenOCD’
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sad i was really hoping to not have to do that
it happens some times… get some more XIOA gear… its still on sale
It happens sometime… just a part of learning… luckly when my bricked… i just put it into a jar and once i found that link to unbrick it… i pulled it out
If both LEDs are on continuously, it might indicate a bootloader issue or that the board is stuck in a particular state. Try a full power cycle and check connections to ensure everything by the copy and paste is properly seated. If the problem persists, consider re-flashing the bootloader.