[SOLVED] SIM900A AT Commands to connect to TCP server over GPRS

[mrinalsahani]

HI,

I bought the SIM900A module few days back. I am able to initiate/receive calls/SMS. But I am not able to connect it to the internet over GPRS. Couldn't find a AT Command list with description in English. The only one AT commands document I found from SIM official website is in Chinese :shock:

If you can share the full AT command set document in English, or, AT commands sequence that I need to execute to connect the SIM900A to the TCP socket of any server and send data over GPRS, It will be very helpful.

Thanks in advance,
Mrinal

 

[FvM]

As far as I know, the SIM900 user manuals can be downloaded from SIMCOM for registered customers. But you'll find at lot of these documents (recent and previous releases) when searching with Google.

Unfortunately the documents are officially prohibited from public disclosure, so they can't be published at Edaboard.

 

[xpress_embedo]

Check these links.

https://www.pantechsolutions.net/blog/basic-at-commands-for-sim900a-gsmgprs-module/


SIM900 and SIM900A are almost similar.
https://lmgtfy.com/?q=SIM900+AT+Commands

 

[mrinalsahani]

As far as I know, the SIM900 user manuals can be downloaded from SIMCOM for registered customers. But you'll find at lot of these documents (recent and previous releases) when searching with Google.

Unfortunately the documents are officially prohibited from public disclosure, so they can't be published at Edaboard.

Yes, SIM900 AT commands manual is available in English language. But I am trying to find SIM900A AT commands manual, which is also available there but only in Chinese language. :-(

Check these links.

https://www.pantechsolutions.net/blog/basic-at-commands-for-sim900a-gsmgprs-module/


SIM900 and SIM900A are almost similar.
https://lmgtfy.com/?q=SIM900+AT+Commands

Yes, SIM900 and SIM900A are similar but unfortunately not the same. Similarity is the reason I am able to initiate call/receive call/Send SMS/Receive SMS. But I am not able to connect to the server using SIM900 AT command set because both are not same.
Thanks a lot for educating me, I had seriously no idea what Google does :roll:

 

[dizgah]

hi
review this file:
https://s5.picofile.com/file/8148556334/_2013424143835f.pdf.html
its sim900 ip application manual & describe http protocol over gprs completely
if have any problem ,ask it
: )

 

[xpress_embedo]

Yes, SIM900 and SIM900A are similar but unfortunately not the same. Similarity is the reason I am able to initiate call/receive call/Send SMS/Receive SMS. But I am not able to connect to the server using SIM900 AT command set because both are not same.
Thanks a lot for educating me, I had seriously no idea what Google does

I am using SIM900 manual and using SIM900A, and had successfully done following things:-
Receiving Call
Disconnecting Call
Sending SMS
Receiving SMS
Connecting with GPRS (TCP and UDP Both)
Send data to a TCP Server.

and everything works fine.

 

[FvM]

I am using SIM900 manual and using SIM900A, and had successfully done following things:-
Receiving Call
Disconnecting Call
Sending SMS
Receiving SMS
Connecting with GPRS (TCP and UDP Both)
Send data to a TCP Server.

and everything works fine.

This has been also my guess. Up to now, SIMCOM was trying to keep AT command interfaces basically compatible between modem families. There are however new functions and enhancements of existing functions. As far as I see, there is a dedicated AT command manual for SIM900A available, but the TCP related application notes cover all recent modems. Your vendor should supply the SIM900A AT command manual nevertheless.

 

[mrinalsahani]

Thanks to FvM, dizgah and xpress+enbedo.

I was left with three options:
1. Learn Chinese to understand the only AT datasheet for SIM900A which is in Chinese.
2. Learn Urdu/Farsi to understand the web page shared by "dizgah" above.
3. Map the AT Commands from Chinese SIM900A AT document to English SIM900 AT document and give it a try.

I tried 3rd option and that worked. Here are the sequence of AT commands with a little explanation that worked for me. Hope it this detail will help anyone who is interfacing this module for the first time.

AT+CGATT? [To check if GPRS is enabled or not]
[Response "+CGATT: 1" indicates it is attached, else try sending "AT+CGATT=1" ]


AT+CIPSHUT [Close the IP session if any]
[Response should be "SHUT OK"]

AT+CIPSTATUS [Check if the IP stack is initialized]
[Response "STATE: IP INITIAL"indicates IP stack is initialized]

AT+CIPMUX=0 [Setting up a single connection mode]
[Response "OK" indicates single connection mode set successfully]

---This should be done one time to save the access point------------------------
AT+CGDCONT=1,"IP","airtelgprs.com";
[Response should be "OK", you can verify the entry by sending "AT+CGDCONT?"]
--------------------------------------------------------------------------------

AT+CSTT="airtelgprs.com"; [Select the accesspoint, append 2 more params if needed-> ,"username", "password" ]
[Response should be "OK"]

AT+CIICR [ Connects to the service provider. Response might take some time]
[Response should be "OK"]

AT+CIFSR [Get the local IP address]
[Response should be "IP address" assigned to the module]

AT+CIPSTART="TCP","180.152.200.105","80" [Start the connection, TCP, domain name, port]
[Response should be "OK" and after sometime "CONNECT OK"]

AT+CIPSEND [Request initiation of data entry which you want to send]
[Response should be the string “>” to indicate that you can send the data]
[You need to send a byte with value 0x1a to let the module know that is the
end of the data you want to send]
[Module should reply with "SEND OK"]

AT+CIPSHUT [Request shutting down of the current connections]
[Response should be "SHUT OK"]


Thanks,
Mrinal