Interfacing a microcontroller with a modem - Electronic Circuits Projects Diagrams Free

matt_d82 · 18th March 2004, 11:01 PM

I am working on a project in which a microcontroller needs to transfer data to a computer over a modem and telephone line. I will be using a microcontroller that has a built-in UART (8051 family, AT89S53). I am looking for the easiest way to do this.

I don't know much about serial communications and I don't have a lot of time to learn it. I was hoping it would as easy as connecting a few lines between the microcontroller and the modem. Then just sending modem commands (AT commands) and data over the microcontrollers UART to the modem, and have everything else know what to do.

Does anyone know of a very simple modem IC to do the job? Even using a regular external modem may do the trick. I've seen a few "modem" ICs but they have like 40+ pins. I was hoping for something much simpler. Is there some other easier way to accomplish this? Does anyone know of any good tutorials or other information on interfacing a microcontroller with a modem IC?

Thanks!

Matt

**Nigel Goodwin** · 19th March 2004, 09:09 AM

Quote:

Originally Posted by matt_d82

I am working on a project in which a microcontroller needs to transfer data to a computer over a modem and telephone line. I will be using a microcontroller that has a built-in UART (8051 family, AT89S53). I am looking for the easiest way to do this.

I don't know much about serial communications and I don't have a lot of time to learn it. I was hoping it would as easy as connecting a few lines between the microcontroller and the modem. Then just sending modem commands (AT commands) and data over the microcontrollers UART to the modem, and have everything else know what to do.

Does anyone know of a very simple modem IC to do the job? Even using a regular external modem may do the trick. I've seen a few "modem" ICs but they have like 40+ pins. I was hoping for something much simpler. Is there some other easier way to accomplish this? Does anyone know of any good tutorials or other information on interfacing a microcontroller with a modem IC?

Just use an external computer modem - all you need to provide it with is RS232 serial data, a MAX232 will interface from your processor, and you just need to write the software to communicate over the RS232 link.

It couldn't get any simpler, if you try and control a modem IC directly, it would be many, many times more complicated - an external modem already includes a micro-processor, which does all the hard work for you!.

matt_d82 · 20th March 2004, 06:42 PM

That sounds like a good way to go. Thanks Nigel!

jem · 21st March 2004, 02:43 AM

Hi Matt:

Don't know where you live, but I have successfully used Multitech embedded modems (www.multitech.com). They have a whole selection of modems with different price/preformance (mostly speed) ratios. I typically use their 2400 Baud modem because it is cheap ($25 approx.), and I do not not need high speed anyway for my embedded applications.

Initialization is quite simple. Typically you just send a single initialization string consisting of some AT, &S, and &W commands.

Hope that helps!

Jem

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18th March 2004, 11:01 PM	(permalink)
matt_d82	Interfacing a microcontroller with a modem I am working on a project in which a microcontroller needs to transfer data to a computer over a modem and telephone line. I will be using a microcontroller that has a built-in UART (8051 family, AT89S53). I am looking for the easiest way to do this. I don't know much about serial communications and I don't have a lot of time to learn it. I was hoping it would as easy as connecting a few lines between the microcontroller and the modem. Then just sending modem commands (AT commands) and data over the microcontrollers UART to the modem, and have everything else know what to do. Does anyone know of a very simple modem IC to do the job? Even using a regular external modem may do the trick. I've seen a few "modem" ICs but they have like 40+ pins. I was hoping for something much simpler. Is there some other easier way to accomplish this? Does anyone know of any good tutorials or other information on interfacing a microcontroller with a modem IC? Thanks! Matt

20th March 2004, 06:42 PM	(permalink)
matt_d82	That sounds like a good way to go. Thanks Nigel!

21st March 2004, 02:43 AM	(permalink)
jem	Hi Matt: Don't know where you live, but I have successfully used Multitech embedded modems (www.multitech.com). They have a whole selection of modems with different price/preformance (mostly speed) ratios. I typically use their 2400 Baud modem because it is cheap ($25 approx.), and I do not not need high speed anyway for my embedded applications. Initialization is quite simple. Typically you just send a single initialization string consisting of some AT, &S, and &W commands. Hope that helps! Jem