Hello.
Yes, it usually okay to connect power to your Arduino’s VIN pin (labeled AVIN on the Motoron shield) while USB is also connected. One issue to be aware of is many Arduinos in some situations could send power into the USB port if the supply voltage falls bellow around 7.4V. There is more discussion about that in this thread, but I do not think that is a concern in your setup since your battery is 12V. However, please keep in mind that powering your Arduino with a 12V SLA battery could be risky depending on what specific model you have. For example, the recommended maximum operating voltage for the Arduino Uno Rev3 is 12V (to avoid overheating), and the voltage of a fully charged 12V SLA battery will probably be higher than that. So, in that case, it might be better to add a an appropriate voltage regulator to your setup as mentioned under the “Powering the Arduino” header in the “Motoron M2S pinout” section of the Motoron user’s guide.
What Arduino are you using, and can you also post some pictures of your setup, including ones that show the top and bottom side of the Motoron so we can check all of the soldered connections?
Does the Motoron’s red error LED still turn on if you power the Arduino from the Motoron and have the USB cable connected? If so, please try the “Careful.ino” example sketch from our Motoron Arduino library with minimal modification (you will need to comment out code that would drive a third channel on the M3S256) and let me know what errors are reported by the Serial Monitor.
- Patrick