Quote Originally Posted by f_lez View Post
I'm trying to connect a 18f2550 to a serial modem (aka phone) problem being the voltage of its serial data is 3v not 5v..

now the device is 5v tolerant and I can send data to it, a simple ATDT123 causes a dialling to occur, problem is I cant receive the ''ok'' that says its acknowledged the dial string.

the 3v data is good enough to brightly illuminate an led (with series resistor!) so i have a good bit of juice, but like i say i cat 'see' it with the serial commands.

any idea if one port would be better than another or some software trick, or am i really going to have to build a level shifter into this and increase the old component count?
Are you running the PIC at 3 volts?

Before you go to all of the hardware trouble it might be a good idea to post your code and configs.