AT Commands for Modems

Hi,

I have been working on a project for interfacing a 3G modem. However, I have been unable to figure out one thing.

I have seen descriptions in which AT commands are used to communicate with the USB modem. But which terminal is used to send these commands to the Modem.

Do we use the Micro-controller itself to send the AT commands to the modem or we are using the PC. And if we are using the PC to send the AT commands, does it mean that we can not use the micro-controller alone to send the AT commands and operate the Modem ?

AT commands are just strings send to a modem over a serial line so any processor that can do serial can send them.

There are some commands that switch mode of a modem, IIRC +++ is one of them.

Also some commands will get extended replies other just an OK msg. These answers indicate the state of your modem.