Sparkfun GSM/GPRS SM5100b shield on a Diavolino

I have decided to return the SM5100B evaluation board since I am instead using the SM5100B cellular shield. This is because I was not really going to use any of the interface pins of the SM5100B module broken out on the eval board. One useful thing about the shield (that I wasn’t expecting) is that it is able to reset the cellular module using the on board reset button similar to the eval board.

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The Diavolino board here is running without any AVR 328 mega chip plugged into it, and has the 2.5mm x 5.5mm power barrel socket for the 5V 3A regulated power supply from EvilMadScience.

Diavolino hosting a GSM/GPRS shield

Meanwhile although I can receive TCP data on the SM5100B modem over GPRS I still haven’t been able to successfully confirm transmission of data.

TCP connection over GPRS with SM5100B module

After having no success sending GET requests to HTTP servers I finally decided to set up my own tcp server by directing a port on my router to my PC and setting up a simple tcpserver listener in cygwin like this:

~ > tcpserver -t1000 -v -Bare_we_receiving 0 9876 bash -c "sleep 1000"
tcpserver: status: 0/40

Then I sent the following commands to the modem

AT+CGATT? 
AT+CGDCONT=1,"IP","epc.tmobile.com" 
AT+CGPCO=0,"None","",1 
AT+CGACT=1,1
AT+SDATACONF=1,"TCP","MY_ROUTER_ADDRESS",9876 
AT+SDATARXMD=1,1,0
AT+SDATASTART=1,1

For some reason the MY_ROUTER_ADDRESS had to be the text host name instead of the IP address, which was something like c-blah-blah.comcast.net for me as per my router.

Immediately I saw a connection appear in the tcpserver log:

tcpserver: status: 1/40
tcpserver: pid 5232 from 208.54.32.166
tcpserver: ok 5232 :::ffff:192.168.1.111:9876 :::ffff:208.54.32.166::50107
tcpserver: end 5232 status 256
tcpserver: status: 0/40

And then some data was received on the GPRS modem side:

> +STCPD:1
>

Which I read back promptly:

AT+SDATASTATUS=1
> +SOCKSTATUS: 1,1,0102,54,0,16
> 
> OK
>
AT+SDATAREAD=1
> +SSTR:1,are_we_receiving
> 
> OK
>

And it exactly matched the banner text. So atleast I can establish TCP connections. The AT command interface though is a real pain.