Top-of-head response!
Do you need to communicate with the computer via USB? If not, could you use 0 & 1 to communicate with the GSM shield? Connect two leds to other pins to indicate success or failure when the card is swiped?
Top-of-head response!
Do you need to communicate with the computer via USB? If not, could you use 0 & 1 to communicate with the GSM shield? Connect two leds to other pins to indicate success or failure when the card is swiped?