I'm using a DigiX (Arduino Due based 3.3V) board to connect to a GPRS/GSM SIM908 breakout board. The SIM908 EVB board has the following pins on its RS232:
I've got all three UART TX lines hooked up to the RX Lines (and RX to TX) on my Arduino but the board keeps resetting, which I would guess is some sort of voltage issue (I turned the board off immediately). However there are three MAX3232s on the underside of the board, which I thought would have made it so I could just connect the lines directly to the Arduino. Does anyone know why this might be happening or how to properly connect these two devices?
(The below links are in Chinese):
Here is a SIM908 Hardware guide.