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[SOLVED] [SIIM900 Problems] I can't send a sms message from SIM900

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Joe Thai

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[SIM900 Problem] I can't send a sms message from SIM900

I use usb-uart FT232 to communicate with SIM900......i tried to send a sms, but i didn't work......when I type a command: AT+CMGS="+841224470861"......Return ...>error. I don't know this matter.....who knows, please help me!!!! thks
 

was AT+CMGS="+841224470861" your first command .. ?
You need to initialise .. setup text mode before start to send messages

1) AT - This command is used to check communication between the module and the computer.
For example,
AT
OK
The command returns a result code OK if the computer (serial port) and module are connected properly. If any of module or SIM is not working, it would return a result code ERROR.

2) +CMGF - This command is used to set the SMS mode. Either text or PDU mode can be selected by assigning 1 or 0 in the command.
SYNTAX: AT+CMGF=<mode>
0: for PDU mode
1: for text mode

The text mode of SMS is easier to operate but it allows limited features of SMS. The PDU (protocol data unit) allows more access to SMS services but the operator requires bit level knowledge of TPDUs. The headers and body of SMS are accessed in hex format in PDU mode so it allows availing more features.

For example,
AT+CMGF=1
OK



these should be executed before the AT+CMGS="+841224470861" you are trying
 

amu_cpln said:
was AT+CMGS="+841224470861" your first command .. ?
You need to initialise .. setup text mode before start to send messages

1) AT - This command is used to check communication between the module and the computer.
For example,
AT
OK
The command returns a result code OK if the computer (serial port) and module are connected properly. If any of module or SIM is not working, it would return a result code ERROR.

2) +CMGF - This command is used to set the SMS mode. Either text or PDU mode can be selected by assigning 1 or 0 in the command.
SYNTAX: AT+CMGF=<mode>
0: for PDU mode
1: for text mode

The text mode of SMS is easier to operate but it allows limited features of SMS. The PDU (protocol data unit) allows more access to SMS services but the operator requires bit level knowledge of TPDUs. The headers and body of SMS are accessed in hex format in PDU mode so it allows availing more features.

For example,
AT+CMGF=1
OK



these should be executed before the AT+CMGS="+841224470861" you are trying
Click to expand...

I aslo try like you suggested above, but It hasn't worked up to now, and this is my status picture below. Hope u can help
Untitled.png**broken link removed**
 
Last edited:

the OK reply to the AT message shows that the SIM900 is ready for communication etc etc ..
You get an error only at the last command .. trying to send message ...
check if
1. Your SIM is not locked
2. The SIM has proper signal in the area you are testing
3. The SIM works normally with your cell phone without having to select carrier or other settings
 

amu_cpln said:
the OK reply to the AT message shows that the SIM900 is ready for communication etc etc ..
You get an error only at the last command .. trying to send message ...
check if
1. Your SIM is not locked
2. The SIM has proper signal in the area you are testing
3. The SIM works normally with your cell phone without having to select carrier or other settings
Click to expand...

I'm a student under Automation control Faculty;therefore, some telecommunications knowledges, I don't know actually. Can you give me some more concrete? thanks
 

Have you inserted a SIM card in the SIM slot of SIM900
 

good .. and is that a working SIM card .. i mean can u make calls with that SIM ..
 
Sometimes I can make a call successfully, sometimes It doesn't response.

---------- Post added at 13:35 ---------- Previous post was at 13:31 ----------

of course, I must use a working sim card
 

This is all that i meant to ask in post #4
thanks for the response
The Error message relates to not having assigned a proper SMSC number .. or not allowed to send text message
 

The problem is because of my typing habit, I type double quotes "" first and then I type the phone number between them....for more explicit, I must type each letter in turn left to right until end of a ATcommand.......that must be like that......
 
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