help help with rs232

Dear Frends,

I am using mc35i gsm modem from siemens and want to connect that with my
microcontroller, so for full modem configuration should I connect MAX232
to all the 9(nine pins of full modem) pins of controller or just Tx and
Rx.

thnx n reply

Pankaj

bhimanipankaj wrote:
> Dear Frends,
> 
> I am using mc35i gsm modem from siemens and want to connect that with my
> microcontroller, so for full modem configuration should I connect MAX232
> to all the 9(nine pins of full modem) pins of controller or just Tx and
> Rx.
> 

You are honestly best off reading the manual for the modem, but IIRC the 
TC35 (which I think is the guts of the MC35) will work just with Tx and 
Rx. However, the faff of using god-awful Hayes protocol means you are 
best off with handshake lines connected too, and the ring indicator etc.

I wonder why they didn't just drop the whole antique serial protocol for 
these embedded 3.3V logic modems, and just give us parallel access and 
an interrupt?

Paul Burke

Paul Burke wrote:

> I wonder why they didn't just drop the whole antique serial protocol for
> these embedded 3.3V logic modems, and just give us parallel access and
> an interrupt?

a) the modem emulation firmwar is all a blackbox product, ready rolled?

b) many micros have UARTs...

I assume that by the MC35i is mainly hardware compatible to the GSM
module that I am using:
http://www.gsm-modem.de/pcs-module.html
- As long you are in command mode handshake is not supported
- As soon you change to CSD or GPRS  handshake is on by default
- You can switch off the handshake lines by AT commands

As long you send small packeges of data you will not loose data, but if
you ever try to send bigger volume of data, then you should use
handshake.

Regards
Meff