QT Py SAMD21 Auto Run?

[leafon]

Hi,

I've programmed around 50 pcs of the QT Py - SAMD21 using the same .uf2 file (converted from .bin file using uf2conv.py).

I noticed that on perhaps 30% of the boards, the microcontroller automatically runs after power up. On the rest of the boards, I need to press the reset button to get the microcontroller running. This doesn't seem to be an initial power on issue since I'm using the same board to power them (just swapping the QT Py boards).

This issue persists if I program the boards using the .bin file from Platform IO.

Could this be due to some variation between the QT Py - SAMD21 boards? How do I get QT Py - SAMD21 to run automatically after power up?

[adafruit_support_carter]

What is the code being run? Can you post full code here or link to listing?

[leafon]

Sorry, I can't share the source code.

I noticed that whether the QT Py - SAMD21 "auto runs" is definitely repeatable. I can comment out half of the code, the QT Py that "auto runs" still does. The boards that requires pushing the reset button to run, still needs button pressing.

[adafruit_support_carter]

Unknown then. It may somehow be related to the code.

Can you recreate the issue with shareable code?

[leafon]

Why does the same code behave differently on the QT Py M0+?

I'll try the make the code sharable.

[adafruit_support_carter]

Why does the same code behave differently on the QT Py M0+?

unknown

[leafon]

It appears the reset pin of the ATSAMD21E18 requires a RC delay.

I noticed on the QT Py M0+ that do not "auto boot", if I attach a scope probe to the RESET_N pin, it auto boots every time.