The problem I discovered has to do with your power system. It looks like the Arduino Uno has some kind of isolation built in the perhaps you don’t have between the USB 5VDC input and the external power input jack. I tested using a motor shield from Adafruit with a couple of 4.5 – 9VDC motors. Bottom line is, when I plug 9VDC into the XLR8’s external input jack, it doesn’t seem to like it. It causes a motor test to fail that run perfectly on the Arduino Uno. My previous message was a detailed explanation of exactly how to reproduce the problem but was apparently too long to post.
First off, thanks for trying out XLR8!
I’m interested in figuring out the issue you are seeing. Our power system isolates USB from the barrel power in basically the same way that the Uno does, so it will be interesting to see what’s going on. Feel free to email me directly at email@example.com
Thanks for your help on this.
We weren’t able to recreate the issue you were seeing with the parts that we had around here, but once we got the motors in from Adafruit we got to the bottom of it. Those little guys appear to throw off a lot of EMI and it is getting into the reset line. I’m pretty sure this would be the same regardless of whether you have an XLR8 or Uno. The difference is the Uno has a 2.5us filter on its reset input (sections 1.1.5 and table 29-11 of the Atmel ATmega328 chip spec) and we missed that in our design. One of the cool things about XLR8 is that we can fix things like this. I’ll have a new board package on our website tomorrow that you’ll be able to use to update your board and resolve the issue.