Hello.
I am quite new to arduino and just discovered platformIO today which looks amazing!
I have the exact same problem. It has been driving me crazy all afternoon. Now I change platformio to be platform = atmelsam@3.6.1 and monitor is working.
I notice upload and monitor is too “fast” - the USB magic that happens in teh M0 hasn’t happened yet, but when I do monitor, it seems to work okay.
Is this a bossac problem or …?
I am on win10.
The problem is reproducible with Adafruit M0 wifi feather and an adalogger feather. I will get some other boards so I can test if that helps.
looking forward to using platformIO … fingers crossed.