Hi, can anyone suggest a GSM modem board that can be easily connected to a MOD DEV 70 board.
I have an existing application that connects to a website via ethernet once a minute and uses HTML post commands to send data updates to a database. I have been asked to investigate the possibility of changing the ethernet connection for a GSM modem (USA)and only posting the updates once an hour. The ability to transfer files using FTP and send SMS messages would be usefull as well.
Can anyone point me to any examples of such a GSM board, and details of how to interface the MOD DEV 70 to it and any samples of code needed to establish a link to the internet with it.
Thanks in advance.
Bill Comben
GSM modem for use with MOD DEV 70 board
Re: GSM modem for use with MOD DEV 70 board
Hi Bill,
If you plan to connect via the modules RS232 interface then any one the so called GSM TERMINALS will do the job. Sparkfun have some modules available but they are expensive compared to a ready to use terminal such as those by Wavecom. If your interface is TTL then you will need to have either a custom board or use a TTL to RS232 convertor for the module you wish to use. If you can roll your own hardware have a look at the modems from SIMCOM. I get the latest SIM900 modules for $20 and they are fully certified. You need a power supply and a PCB to use them but it is not that high a value. I can built complete units for less than $50 in quantity or under $100 in 1 or 2 offs.
For software you just need to use the PPP driver that comes with Netburner to make the connection. Make sure you have the latest release as I found some issues with the PPP driver with some modems and my fixes are now included with the latest releases. Pay attention to what is called the MAGIC number. You may need to set this to TRUE if you find that your modem won't connect.
Once your PPP connection is established, you can then do any network operations you need, FTP, HTTP etc. Note that you won't be able to run an HTTP server and connect to it over GPRS (in some cases you can, but only if the operator uses static IP's and most do not)
As for SMS you will have to roll your own code. If you are happy with working with a max of 140 characters instead of 160 then you can use the TEXT MODE for sending messages. This is very easy to do with AT commands. To use the full 160 characters you need to use PDU mode and this will require some work to do the conversion. You might find some code out on the Internet but rolling your own will help to understand how it works.
Note that whilst you are connected via PPP you won't be able to send or receive SMS's unless you where somehow able the use the multplex mode that modems of this type offer. This is a packet based messaging where you can do data at the same time as AT commands but it will require a major change to the Netburner code. This is something I am considering for the future but it is some way off yet.
Hope this helps? If you get stuck just give us a shout as I have gotten GPRS and modems to work with the Netburner and it is reliable.
Dave...
If you plan to connect via the modules RS232 interface then any one the so called GSM TERMINALS will do the job. Sparkfun have some modules available but they are expensive compared to a ready to use terminal such as those by Wavecom. If your interface is TTL then you will need to have either a custom board or use a TTL to RS232 convertor for the module you wish to use. If you can roll your own hardware have a look at the modems from SIMCOM. I get the latest SIM900 modules for $20 and they are fully certified. You need a power supply and a PCB to use them but it is not that high a value. I can built complete units for less than $50 in quantity or under $100 in 1 or 2 offs.
For software you just need to use the PPP driver that comes with Netburner to make the connection. Make sure you have the latest release as I found some issues with the PPP driver with some modems and my fixes are now included with the latest releases. Pay attention to what is called the MAGIC number. You may need to set this to TRUE if you find that your modem won't connect.
Once your PPP connection is established, you can then do any network operations you need, FTP, HTTP etc. Note that you won't be able to run an HTTP server and connect to it over GPRS (in some cases you can, but only if the operator uses static IP's and most do not)
As for SMS you will have to roll your own code. If you are happy with working with a max of 140 characters instead of 160 then you can use the TEXT MODE for sending messages. This is very easy to do with AT commands. To use the full 160 characters you need to use PDU mode and this will require some work to do the conversion. You might find some code out on the Internet but rolling your own will help to understand how it works.
Note that whilst you are connected via PPP you won't be able to send or receive SMS's unless you where somehow able the use the multplex mode that modems of this type offer. This is a packet based messaging where you can do data at the same time as AT commands but it will require a major change to the Netburner code. This is something I am considering for the future but it is some way off yet.
Hope this helps? If you get stuck just give us a shout as I have gotten GPRS and modems to work with the Netburner and it is reliable.
Dave...
Re: GSM modem for use with MOD DEV 70 board
Hi Dave thanks for the wealth of information that you have given me, it will take me some time to digest it all, but it looks like you have covered everything I need.
I will go away and research the modem cards next, this may take me a while, so if you dont here from me for a week or so dont think I have given up.
I am sure I will be back with more questions and will let you know what decisions I made.
Thanks again for your help.
Regards, Bill
I will go away and research the modem cards next, this may take me a while, so if you dont here from me for a week or so dont think I have given up.
I am sure I will be back with more questions and will let you know what decisions I made.
Thanks again for your help.
Regards, Bill