How find out the end of a response reply from SIM300 or SIM900a modem

[dhanraj_kmr]

Hi All,
I have interfaced a SIM300 modem with my PIC16f877a. I am able to send any AT commands to modem and able to make it work. And also i am able to receive one by one character from hyperterminal.

Here my doubt is since GSM modem may send any data at any number of bytes any time, how can i identify the end of character for all response correctly.

I could not find anything from GSM reply msg. All i received had 0x0A at the end. But This comes even in the middle of the msg. So can not judge based on this.

I read that i can configure GSM to send a custom character at the end of all reply. is it true?
Or can i use DTE and DTR to determine the response?

Any Idea?

 

[mathespbe]

Hi All,
I have interfaced a SIM300 modem with my PIC16f877a. I am able to send any AT commands to modem and able to make it work. And also i am able to receive one by one character from hyperterminal.

Here my doubt is since GSM modem may send any data at any number of bytes any time, how can i identify the end of character for all response correctly.

I could not find anything from GSM reply msg. All i received had 0x0A at the end. But This comes even in the middle of the msg. So can not judge based on this.

I read that i can configure GSM to send a custom character at the end of all reply. is it true?
Or can i use DTE and DTR to determine the response?

Any Idea?

0x0A is the is the line feed character. it 'll be received once in a msg Tx...

 

[Venkadesh_M]

Use a receive timeout in the uart module if its not presents in your controller use a software timeout...

 

[ROHITBARAVKAR]

echo back problem

hey how do u solved the echo back problem i am also facing same problem.
& which serial port u r using out of two seial ports of sim 300

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when i send commmand it is getting received back on RXD pin

 

[alokdaga]

you have to turn echo off by sending ATE0

 

[milan.rajik]

Use ATE0 once. Most of the GSM responses end with \r\nOK\r\n. So, you have to check if your buffer contains this string for every GSM response.