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communication between GSM modem and PIC microcontroller

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monika

Tue Apr 08 2008, 10:36PM

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i m using a maestro modem which supports both text and PDU mode. and i m interfacing it with PIC 917.

i m able to send AT-commands using hyperterminal with the modem but when i communicate with the microcontroller, i m not able to get the response of AT-commands.
i m sending a string like this:
putc("AT \r\n");

but it is not giving the required response.....it is not giving OK...
what should i do????
Plz help me on this....

shyam

Wed Apr 09 2008, 12:03AM

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u r using putc ?????
is it meant to send char or string please check and reply!!!

lProgress is not made by early risers or hard workers, but by LAZY people, trying to find easier ways to do the same........

monika

Wed Apr 09 2008, 03:20AM

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i m displaying the output on LCD, for that i have written a code.....
which u can see in the attachment.....
plz tell me where i m wrong.....

one more thing i want 2 know....if i will send msg, then can i write the code for text mode for reading the msg ( no need 4 PDU mode,bcoz my modem supports text mode 2)

include.pdf

Ajay

Wed Apr 09 2008, 08:32AM

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first do check what shyam said.
There are few mistakes you might missed out. There is only carriage return while sending at command. So you don't need \n
also i think you have given space between at and \r which could be the point of error.

to enable text mode do read your modem's manual carefully.

instead of using putc use puts

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monika

Wed Apr 09 2008, 09:50PM

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i already did that. i compiled my code without /n. but result was same. No response of AT-command is comming. and there is no space b/w at and /r.

i can't understand what is the problem with my code.....is there any mistake plz guide me...

shyam

Fri Apr 11 2008, 11:15PM

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first of all please check if ur modem and controller can communicate properly..

u have tested modem with the PC ...

now test ur controler the same way see if u can reeive data from PIC(controller) to the hyperterminal..

lProgress is not made by early risers or hard workers, but by LAZY people, trying to find easier ways to do the same........

monika

Sun Apr 13 2008, 03:37PM

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yes i have tested PIC with hyperterminal..and it is responding fine..
problem arises when i interface modem with PIC.then there is no response on LCD.

my hardware connections are ----

for DB-9 connector-
pins 1,4,6 are connected.
pins 7 and 8 are connected.
5 is ground.
pin 2 is connected to TX of MAX and pin 3 is connected to RX.

Plz check the connections and guide me accordingly....

monika

Thu Apr 24 2008, 08:21PM

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can anybody guide me what can can be the correct schematic for interfacing GSM modem with PIC microcontroller......

i hv done the above mentioned connections bt these are not working when used with modem. these are working fine with hyperterminal.