Metro Mini upload code reliably only without external power

[Systembolaget]

Hej,

I have a bunch of Metro Minis and a one year old MacBook Pro (Catalina). When I supply 6V from a 3A PSU through Vin to any of my Metro Minis, uploading code almost always fails. I can upload code when I disconnect the PSU and only run the Metro Mini via USB. Plugging the PSU plug in and disconnecting the breadboard's DC-jack all the time for each code upload is tedious.

When I boot the MacBook Pro into Windows 10 via bootcamp, I have no such problems when powering via Vin.

Any ideas?

Thanks!

[adafruit_support_mike]

It sounds like your 6V supply might be noisy. That could cause enough interference to mess up the USB signals during an upload.

Output smoothing is one of the places where power supply manufacturers can cut corners. Good filters tend to be large and expensive, or small and really expensive, and the only way to see the output quality is by connecting it to an oscilloscope.

Try adding a large capacitor (100uF to 1000uF) between the Vin and GND pins. That should smooth the power enough to make the USB connection happy.

[Systembolaget]

Thanks, however, I have a capacitor in place and it happens with other PSUs as well, on any Metro Mini. It also happens with Metro and Feather Huzzah 8266. On all four USB-C ports of the Mac. It never happens when using the Mac in Windows 10 mode via bootcamp.

[adafruit_support_mike]

In that case I have no idea what could be happening. The supply voltage should have no effect on the USB connection.

[Systembolaget]

Ok, thanks; it certainly must be a macOS Catalina thing. I saw many other posts on the Internet with similar issues when using macOS.