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Need some facts about GSM modem

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ADGAN

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Need some facts about GSM modems

Hi! I need a GSM modem ONLY to send a SMS. SMS contains a numerical value. Which mode should I use text mode or PDU mode? This is the GSM modem I'm hoping to use in my project
siemens-sms-gsm-tc35-tc35i-development-board-module-uart-rs232-ttl-at-commands_1_.jpg

Is it possible to send a messages from the microcontroller without using the serial port instead using the RX TX pin. It says it support serial R232 and TTL. So do I require a MAX232 IC ?
Is there any other model which does not come with a serial port & a power connector ? Since I'm hoping to produce a compact design for the project I prefer to have a GSM modem which does not have a serial port & a power connector
 
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You can use text/pdu mode.Better option is the text mode.

You can connect RX TX pin directly to TTL out of the modem brekout board.

if it supports RS232 then there will be a max232 in the board and use that when you connect the modem to a PC.

The better option is to use a sim300/900 modem without breakout and do the necessary connection yourself.There are lots of schematics available on the internet.just google for it.

Hope it helps!
 
Should I connect the Rx and Tx pins of GSM modem to the Tx and Rx pins of 8051 microcontroller for cross cable as I am not able send sms using only serial cable
 

I think you should connect Rx-Rx and Tx-Tx, is this the board you are using?
 
First you need to synchronize the modem with MCU. sending AT command to modem, will reply OK. if so then send AT+CMGF=1, that will setup the modem to text mode. and then send AT+CMGS='phone number', send Ctrl+Z. That will send a sms to the given number. Also read the datasheet of the modem you are using.
 
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