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Topic: SIM900: GSM-Module is no longer working. How to reset? (Read 19009 times) previous topic - next topic

FelixGroup

Hello

I am using a SIM900 GSM shield in combination with an Arduino Uno and the open electronics library (https://code.google.com/p/gsm-shield-arduino/).

Yesterday I send one new AT command in the GSM_GPSLibrary_AT example to the module. It was "AT+CSCLK=1" to disable slow clock which will cause, that the module will not go in the sleep mode.

But since then, my GSM library can not start the module. I tried a lot.  Now I connect my computer direct the the UART port of the SIM900 and I log the commands. I send the following to reset the module:
Code: [Select]
    gsm.SimpleWriteln(F("AT+CSCLK=0"));    //DISABLE SLOW CLOCK
    delay(2000);
    gsm.SimpleWriteln(F("ATZ"));                //RESET DEFAULT CONFIGURATION
    delay(2000);
    gsm.SimpleWriteln(F("AT&F"));              //FACTORY DEFINED CONFIGURATION
    delay(2000);
    gsm.SimpleWriteln(F("AT+CFUN=1"));     //FULL PHONE FUNCTIONALIY


But it is no solution. The module will no communicate with the Arduino any longer. If I power up the SIM900 through the power on impuls, it will start and show this:
Quote
AT
AT
AT
AT
AT
AT&F
ATE0
AT+CLIP=1
AT+CMEE=0
AT+CMEE=0
AT+CMEE=0
AT+CMEE=0
AT+CMEE=0
AT+CMGF=1
AT+CMGF=1
AT+CMGF=1
AT+CMGF=1
AT+CMGF=1
AT+CNMI=2,0
AT+CNMI=2,0
AT+CPMS="SM","SM","SM"
AT+CPMS="SM","SM","SM"
AT+CPMS="SM","SM","SM"
AT+CPMS="SM","SM","SM"
AT+CPMS="SM","SM","SM"
AT+CPMS="SM","SM","SM"
AT+CPMS="SM","SM","SM"
AT+CPMS="SM","SM","SM"
AT+CPMS="SM","SM","SM"
AT+CPMS="SM","SM","SM"
AT+CPBS="SM"
AT+CPBS="SM"
AT+CPBS="SM"
AT+CPBS="SM"
AT+CPBS="SM"
AT+CIPSHUT
AT+CIPSHUT
AT+CIPSHUT
AT+CIPSHUT
AT+CIPSHUT
ATE0
AT+CSCLK=0
AT+CSCLK=0
ATZ
AT&F
AT+CFUN=1



Is it destroyed? Or is it a bug of the firmware? I posted it as a bug in the Github->Issues of the library. Thank you for all hints:
https://code.google.com/p/gsm-shield-arduino/issues/detail?id=86



Felix

j514

From reading comments in Russian and elsewhere I get the idea that you need to pull DTR high and then issue your AT commands.  Until you reset with an AT&F and then issue an AT+CSCLK=0 the chip will always go to sleep until this happens.  I don't own this device so it's hard to confirm.

Here's the info translated from Russian:
http://translate.googleusercontent.com/translate_c?depth=1&nv=1&rurl=translate.google.com&sl=auto&tl=en&u=http://electronix.ru/forum/lofiversion/index.php/t85857.html&usg=ALkJrhixkDj3_-_9HXPvTb5gctB4QnYL_g
a][+ ascii express, 110/300 novation cat, xmodem

FelixGroup

This is a great idea. I will directly check it. With this hint I found the following information in the datasheet (file attached). This may also explain why I receive the information "ERROR: SIM900 doesn't answer. Check power and serial pins in GSM.cpp" from the SIM900 Library.


j514

That says a lot about the quality of google translate.
a][+ ascii express, 110/300 novation cat, xmodem

FelixGroup

I checked it and you gave me the solution. The things I had to do:

- disconnect the Arduino from the SIM900 RX/TX pins
- connect a Serial Adapter directly to the SIM900 RX and TX pins (pin 9 serial RX, pin 10 serial TX)
- by default (in my case) choose terminal baud rate to 28800 baud + break line command (CR)
- PULL DTR PIN TO HIGH!

To check if the serial communication is working start with command:
AT
the answer should be:
OK

Now I only had to type:
AT+CSCLK=0
OK
AT&W
OK

Ready.
Thank you for that great hint with DTR.

paranoidok

Hello,I have the same issue,  It should be obviously, but How can "PULL DTR PIN TO HIGH"? where can I find de DTR PIN in SIM900 Shield?

dannable

Pin 3 (spot top left corner, third in down) on the SIM900 is the DTR pin. It may be broken out on your board somewhere.
Beginners guide to using the Seeedstudio SIM900 GPRS/GSM Shield

Marciokoko

I dont have a shield, just a breakout module.  How do I access the dtr pin physically?

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