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    GSM module sending Garbage value.

    When antenna is connected to GSM module, it starts giving garbage values. And if you want to execute any commad it starts giving this +CREG 0 then +CREG 2 after that +CREG 1.
    GSM is connected to PC using USB to TTL converter. I am using terminal software(putty).
    Lithium Ion battery, 4.4v, is used to power.

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    Re: GSM module sending Garbage value.

    What GSM module?
    What TTL to USB converter?

    The message suggests you have a poor GSM signal, the different messages say it is having trouble connecting to the network.

    Brian.
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    Re: GSM module sending Garbage value.

    sim900a GSM module.

    What do you mean by poor GSM signal.



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    Re: GSM module sending Garbage value.

    Hi,

    I assume it's caused by your wiring.
    --> show us a couple of detailed fotos of the wiring. Power supply, serial connection, modem...

    Klaus
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    Re: GSM module sending Garbage value.

    At first it was operational with the same wiring, power supply and serial connection. but suddenly it started giving garbage values.



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    Re: GSM module sending Garbage value.

    Maybe it got damaged because it did not had 5V TTL level pins for UART and you directly connected it with 5V MCU's UART pins without using a voltage level translator.

    4.4V from battery powers GSM modue but did you set TTL2USB adapter voltage selection jumper to 3.3V side and connected UART pins of it to GSM module? If the jumper on TTL2USB adapter was set to 5V and you connected its UART pins to GSM module then your GSM module's UART module is damaged.



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    Re: GSM module sending Garbage value.

    im using pl2303 usb to ttl. it gives 3.3v at UART pins



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    Re: GSM module sending Garbage value.

    Those messages are telling about the connection state to the network. They are saying it is intermittently able to connect, which implies a weak or corrupted link to the GSM network. If there was a problem with the serial link it would show as random characters, not complete messages.

    +CREG is the message sent when the module connects, disconnects or is retraining it's data stream to the cell station. Nothing whatsoever to do with the USB link.

    Brian.
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    Re: GSM module sending Garbage value.

    Click image for larger version. 

Name:	GSM.PNG 
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ID:	152505
    This is a screenshot of the GSM response.

    This time again, at first it was working. But when i tried to send a massage network was disconnected. Could it be the problem in antenna?
    What should I do?
    Click image for larger version. 

Name:	GSM1.PNG 
Views:	8 
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ID:	152506
    Click image for larger version. 

Name:	GSM2.PNG 
Views:	7 
Size:	5.1 KB 
ID:	152507



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    Re: GSM module sending Garbage value.

    Looks like multiple problems at once.
    - changing CREG: either antenna or power supply problem
    - garbage characters: UART problems, defective modem or a strange kind of broken modem configuration. Try reset to factory configuration
    - implausible ERROR messages: different possible reasons, use verbose error messages for distinction

    Generally regarding "suddenly it started giving garbage values". Looks like broken solder joint, defective power supply or modem.



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    Re: GSM module sending Garbage value.

    The module works properly, for commands which don't need network connection, only till it is not searching for network, either you have removed the sim-card or antenna is disconnected.

    The persists during connectivity.

    UART works fine until the module starts searching for the network.

    Some times, once in a while, it does connect to the network and works normal. After some time it goes to the same condition.



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    Re: GSM module sending Garbage value.

    The symptoms still suggest the problem is due to signal strength. If the USB link was faulty you would not see the correct characters at all.
    It could be due to the power source you use, those modules consume a lot of current when transmitting and the actual amount depends on the signal strength at the cell base station. If your power supply is inadequate, the voltage could be dropping during transit bursts and resetting or corrupting the data flow.

    Can you show us how you are powering the module and USB interface please.

    Brian.
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    Re: GSM module sending Garbage value.

    I have tried many different power supplies but could not help.

    Can this problem induce due to the restrictions on GSM Devices in the country??

    Or unregistered device??



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    Re: GSM module sending Garbage value.

    As a quick test to check whether you have issues with insuficient power supply capacity, and if you have the chance, try making experiments with different telephony operators (e.g replacing current GSM module SIMcard by another) which do not share the same radio base station antennas. If incoming signal strenght is weak, it will force the RF stage of the module to drain more power.

    Anyway, just out of curiosity, I would suggest you try monitor received data with a terminal capable of displaying non ASCII data just to check if there exists some pattern on the "garbage" characters, even thought from the images above it seems to happen quite randomly.
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    Re: GSM module sending Garbage value.

    i have tried different simcards of different operators. i think this is not the issue.



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