Problem with AVR and Modem

[icabrera]

Hello!

I've a problem interfacing a modem with AVR. I'm working in a remote control via Telephone.

I use a US Robotics 56K Modem and AT90S8535 (in STK500).

I connect the modem with PC by RS232 Port, from Hyperterminal i use AT Commands to control the modem. By example, ATD5286 (Calling to other extension), Auto answer, config the modem and other things.

But in the AVR i make a program that sends ATD5286 by RS232 Port... (in order to dial up with the AVR) and the modem doesn't respond. No lights, nothing.

By last, i connect the AVR with Hyperterminal and i can see the commands that i sent with MCU.

Anyone who can help me???

 

[Nigel Goodwin]

Hello!

I've a problem interfacing a modem with AVR. I'm working in a remote control via Telephone.

I use a US Robotics 56K Modem and AT90S8535 (in STK500).

I connect the modem with PC by RS232 Port, from Hyperterminal i use AT Commands to control the modem. By example, ATD5286 (Calling to other extension), Auto answer, config the modem and other things.

But in the AVR i make a program that sends ATD5286 by RS232 Port... (in order to dial up with the AVR) and the modem doesn't respond. No lights, nothing.

By last, i connect the AVR with Hyperterminal and i can see the commands that i sent with MCU.

Anyone who can help me???

It's a simple enough thing really, the AVR isn't sending data (or at least the correct data) to the modem. Are you using a MAX232 to give try RS232 levels?, and do you have your transmitted polarity the correct way round?.

Another thought! - are you sending CR/LF at the end of your text string?, and does the modem require that?.