GSM interface to PIC16F690

[lokeshbhatt]

Hi

If anyone has done GSM interface to PIC16f690 uart than please help me b'coz last 7days I'm trying to collect response from GSM, but unable to obtain.
Is there any baud rate issue?
As I'm giving command AT, then GSM gives OK, then it is showing it on hyperterminal, but not getting stored in any variable.
As at initialization of gsm SIM300 it gives response like this:

RDY

+CFUN: 1

+CPIN: READY

+CREG: 1,"3E84","6ACE"

but my controller is not collecting any single of this string.
I'm totally fedup of this CCS compiler.

do anybody has faced this situation before.
I would be grateful to you.
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Thanks & Regards
Lokesh Bhatt

[John Morley]

Hi Lokesh,

It's not enough to be 'fed up'.....

A search of the forum archives yielded four pages of hits using the keyword 'GSM', and there are literally thousands of posts related to serial interfacing in the forums....

What I'm saying is that you've got to take some initiative, and do more than just say 'it doesn't work, please help!'

What code have you already written? Which GSM module are you using? How is it connected to the PIC?

Again, there are many here that would be happy to help, but you've got to take the first step..... Chances are that your problem has a (relatively) simple solution....

John
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John Morley

[vjn86]

Literally you are saying that the modem works fine when connected to the hyper terminal and doesn't work as you expecting when you connecting it with controller..
If this is what you meant, I had similar trouble till yesterday too.

1. You must be using a cross RS232 cable to connect the GSM modem and the pic circuit right ? If yes, try to short PIN7 and pin 8 on the both side of the cable head (rs232 connector) itself.

2. When PC and GSM communicates, the handshaking protocol (RTS and CTS) on RS 232 is utilized. Meanwhile, the RS 232 on micro controller doesn't support this as only TX, RX and GND is used.

3. So, when you short pin 7 and 8 on the cross cable, you are making the GSM modem to be always ready to receive and send data.

Hope this helps you..let me know your progress on this.

with regards
vijay

[Ttelmah]

As a further comment, if the module works directly connected to hyperterminal, then it is talking RS232, not TTL async (which is what the PIC generates). If so, then you have to add at the very least software/hardware signal inversion, and properly a level translator/inverter.
As another poster says, you need to tell us a lot more:
What GSM module?.
How have you had it working - what connections?.
How have you got it wired to the PIC?.
How is it powered?.
How is the PIC powered?.
What 'support' components have you got round the PIC - decoupling capacitors, oscillator etc. etc..

etc. etc..

Best Wishes