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LinkSprite SIM900 modem not working

SIM900 GSM LinkSprite

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#21 chain

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Posted 22 April 2015 - 05:27 AM

Hi Chain,

 

I have tried sending AT command to SIM900 using realterm and still the SIM900 is not responding. I see that Tx LED on the TTL2USB blinks everytime I send the AT command, but Rx does not respond....

 

Any other ideas that I can try, please this is delaying my project :-(

Did you press the power on button of SIM900 shield ?



#22 thandana

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Posted 05 May 2015 - 02:21 PM

Hi Chain,

 

This SIM900 power button was pressed and the GREEN LED was ON, the network status LED was also flashing. I will try and set the baud rate to 19200 using the below command on realterm

 

AT+IPR=19200

 

I will update you on the result of this command shortly.



#23 thandana

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Posted 05 May 2015 - 04:55 PM

Hi Chain,

 

As I mentioned before, when I send AT command to SIM900, I dont get response from it. I'm sending a simple AT command and no response on the realterm serial program. I have tested that the TTL2USB is OK.



#24 chain

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Posted 11 May 2015 - 01:21 AM

Can you try to exchange the Rx and Tx wires of TTL2USB?



#25 thandana

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Posted 21 May 2015 - 08:13 AM

Hi Chain,

 

The modem is now receiving the AT commands. I just needed to switch to Xduino on the board.

 

I picked up another issue while testing the modem, it seems like I cannot receive SMS. I can send an SMS from the modem successfully however I cannot receive SMS. Can you advise on this. After sending SMS, i get this +CMTI: "SMS",3 and NO SMS is shown.



#26 chain

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Posted 25 May 2015 - 09:26 AM

Hi Chain,

 

The modem is now receiving the AT commands. I just needed to switch to Xduino on the board.

 

I picked up another issue while testing the modem, it seems like I cannot receive SMS. I can send an SMS from the modem successfully however I cannot receive SMS. Can you advise on this. After sending SMS, i get this +CMTI: "SMS",3 and NO SMS is shown.

Maybe it need another AT command to  show you the SMS, you can read its AT command manual.



#27 quique

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Posted 08 October 2016 - 01:00 PM

Sorry to hijack this thread but the OP asked about CPMS error.  Ive been playing with a SIM900 myself and discovered that when using the library from here: 

 

https://github.com/M...GPRS-GPS-Shield

 

and a MEGA the sms is sent successfully.

 

But when I use the following AT Command sketch without the library:

void sendData(double temp, double hum){
  sim900.begin(9600);
  delay(5000);
  sim900.print("\r");
  delay(1000);
  sim900.print("AT+CMGF=1\r");
  delay(1000);
  sim900.print("AT+CMGS=\"+504mynumber\"\r");
  delay(1000);
  sim900.print("Temp=" + tempString +  "Hum=" + humString + "\r");
  delay(1000);
  sim900.write(0x1A);
}

it fails to send the message!  This sketch did work once, in between a bunch of tries, and no more.

 

I believe something gets done from within the library, that doesnt get done in the AT command sketch, that fixes the CPMS error.  How could this affect sms sending and how do I fix it?







Also tagged with one or more of these keywords: SIM900, GSM, LinkSprite

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