GSM modem / module - first steps
Please feel free to have a look at GSM FAQ on this homepage as well.
Introduction
These tips should make it easier for you to operate your GSM modem / module. Please read the hints carefully.
Important AT-Command Sets
Please refer to the manual for the return codes of AT commands. Most of the AT commands are followed by [Enter]. If not we show it in the examples as below:
Enter PIN
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AT+CPIN="xxxx"[Enter] Give PIN to the device- important information - enter CPIN before all other commands or try to get SIM cards without PIN |
Activate saved parameters
ATZ[Enter] Activate user profile
Example: Changing and saving parameters
AT+IPR=2400[Enter] Set transfer rate to 2400 bps
AT&W[Enter] Save parameters to memory
Send and Receive
Example: Data transfer
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AT+CPIN="xxxx"[Enter] |
Enters PIN |
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AT+CREG?[Enter] |
Register Network (0,1 means logged in) |
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ATD05111234567[Enter] |
Data call |
Example: Send SMS with GSM modem / module
Enter SMS-Center
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AT+CSCA=+491722270000[Enter] |
Enter SMS-Center for Vodafone Germany |
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AT+CMGF=1[Enter] |
+CMGF=1 - Set modem in text mode |
Example: Receive SMS
A SMS will be stored in the GSM modem / module and being send via RS232 to the peripherals. The peripherals have to send commands to the GSM unit to receive SMS and to erase SMS from the SIM card in order to clean memory.
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+CMTI:"SM",x |
X stands for the memory number of received SMS |
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AT+CMGR=X[Enter] |
Read SMS on memory number X |
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AT+CMGD=X[Enter] |
Erase SMS on memory number X |
Example: Send voice call
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AT+CREG?[Enter] |
Register Network (0,1 means registered in home network) |
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ATD05111234567;[Enter] |
The only difference to issue a data call and a voice call is the semicolon. The transmission of any GSM device is digital so the ISDN-profile (bearer type) is being sent to the receiving ISDN station. If you dial a ISDN voice device with data transmission, the ISDN device will not ring! |
Note: The answers for networks and field strength can be delayed for several seconds.
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ATZ;E[Enter] |
Echo OFF |
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ATZ;E1[Enter] |
Echo ON |
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AT+CSQ[Enter] |
Show field strength. Field strength in dBm = -112 dBm+(2*X). When X gets bigger, then the field strength is higher. -104 dBm is the lowest value for a voice call. A data calls willfaulty because the noise is to high. |
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AT+CREG?[Enter] |
Answer 0,x (X=2=log off, X=1=log in, X=0=don´t know) please refer to manual for further infos |
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AT+COPS?[Enter] |
Shows which GSM operators is active. |
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AT+COPS=?[Enter] |
Shows all available networks |
