Serial Voltages? Serial2Mobile

I am trying to interface a cell phone to an arduino serial port. Like the serial2mobile library, except using the actual serial port instead of softwareSerial.

I have used the software serial library to send data to the phone and it works fine. But I want to use the serial port instead. When I plug in the TX, RX and GND wires to the phone from the arduino, the screen starts to flicker. I can communicate with the phone from a PC without any problems using a blueSmirf hooked directly to the phone. Can anyone help me figure out why I cant communicate to the phone through just the arduino on the Serial port?

Are the signal voltages different from the bluesmirf and the arduino?

hi there coconut924 did you ever found a solution i am looking for the same thins and without using a computer to sende th info to arduino hugs bern

I you are using your Arduino at 5 volts the you need a voltage level converter. this Logic Level Converter will do the work. If you want to build it yourself then see MAX3232.