I'm testing a sim900 GPRS-GSM shield + Arduino Uno. I see there are several ways to power:
a) feed the sim900 through its jack (5V 2A) and feed the Uno through its jack or its USB
b) feed the sim900 through its jack (5V 2A) and feed the Uno with a cable from 5V of sim900 to 5V of Uno.
If I use the solution b) would there be any problem when I connect my Uno to the PC with the usb cable? Because it also receives 5V from the USB, I do not know if can cause any problem the coexistence of both feeds.
I appreciate your help.