Gemma won't enter bootloader mode

[gwells]

I plugged my gemma into two separate Macbook pros, to upload code using the Arduino IDE and couldn't get it to enter bootloader mode. The red light turns on dimly for about 3 seconds and then shuts off. I've used a variety of micro USB cables which I know to be good and none of them solved the problem. I was able to get it to enter bootloader mode twice (after messing with it for about two hours) but each time was isolated and the IDE wouldn't recognize the board either time. These occurrences seemed random which leads me to believe it's a hardware issue and maybe I jostled it just right? I'm thinking it might be a defective board but I don't want to jump to conclusions. I'm relatively new to this but I've tried all of the solutions on the forums that seem to fit my problem without success. I've included a picture of my gemma. The solder is only there in preparation for my project, I never actually wired anything up. Any ideas??

[adafruit_support_mike]

That's a USB problem. MacBooks support USB-3, which uses signals about fifty times as fast as the Gemma's CPU. The poor little thing just can't keep up, so it goes into an endless reboot cycle (which is what makes it look like the LED is dim).

You can usually solve that by putting a cheap/old USB-2 hub between the Mac and the Gemma. I have one that I use with my own MBP any time I need to connect to a Trinket or Gemma.

[gwells]

So I just checked the specs on my MacBooks and one of the two I tried is a 2008 model with USB 2.0 built-in. Is there something else I could be missing? (like, do I need to use a hub regardless or something?) Thanks!

[adafruit_support_mike]

Give it a try. The 'dim red LED' is the most typical symptom of a USB problem.

[gwells]

Yeah, that totally did it, thanks so much!

[adafruit_support_mike]

Glad to hear it. Happy hacking!

[marlauckas]

My new laptop (Lenovo ThinkPad X1 Yoga Gen2 running Win10) is also a "no-USB-2.0" fly-zone. I've tried three different USB 2.0 Hubs (varying ages), but I still can't get Gemmas or Trinkets to be recognized (Port selection grays out in the IDE). Is there anything else I can try?

[adafruit_support_mike]

The Gemma and Trinket will never register as Serial Ports in the Arduino IDE. They don't have any real USB hardware, so the computer only recognizes them while the bootloader is running and emulating a low-speed USB connection.

There's more information in the tutorials:

https://learn.adafruit.com/introducing- ... bootloader
https://learn.adafruit.com/introducing- ... bootloader

[marlauckas]

Thanks Mike, it's working properly now.

Hey Kids! Uncle Matt here with a pro tip: Never assume a NEW usb cable is a GOOD usb cable.

[adafruit_support_bill]

Sad, but true. And the corollary to that rule is: High prices and gold plated connectors are not a reliable indicator of cable quality.