RPi + GSM/3G module + SIM card

RE: RPi + GSM/3G module + SIM card

Former Member — Tue, 26 Feb 2013 16:05:48 GMT

I just figured out that the Pi was likely rebooting due to rf interference from the Huawei stick to the Pi.

I placed an usb cable between the Pi and the stick so that I could locate the stick away from the Pi, and things started to work.

I did solder a polyfuse over the one alrerady on the board. This increases the TP1 - TP2 voltage with 0.1 - 0.2V

External modems like the Siemens, Wavecom and Telit ones use an external antenna. Their reception will likely be better due to that.

They usually also sell OEM modules of their product range. Wathever solution you choose, the way to program them is very similar.

There can be minor differences in the AT command set. Sending sms is pretty easy. Receiving them usually involves polling a number of reception slots to see if they contain a message.

RE: RPi + GSM/3G module + SIM card

Former Member — Tue, 26 Feb 2013 12:30:56 GMT

Hmmm...

I didn't think of sending SMSs using a 3G dongle.

Good idea, Luc Cool, thanks!

I have 4 or 5 USB 3G sticks laying around (most of them Huawei and ZTE), and also an externally powered USB hub, so I guess I could try one out, especially since my 3G provider gives free SMSs between its subscribers

Still, I think I'd rather use a Pi-compatible GSM/3G module for its power consumption and stability.

I don;t really trust these 3G dongles. I used 2 of them with a tablet, and with one of them the temperature of the tablet would rise pretty much after 1-2h, and with the other, the stick would heat up in about 30-45 min. So I don't want to chose this as a final solution just yet.

I am still open to suggestions.

RE: RPi + GSM/3G module + SIM card

Former Member — Mon, 25 Feb 2013 17:31:09 GMT

Most 3g modems can do both gprs and sms.

They indeed rely on the an extended AT command set.

You can use an usb stick 3g modem or you can use one with a serial port like the Siemens TC35i

The Pi is still having issues with usb 2 serial devices. It wouldn't suprise me that a 3g modem appears as such a device to the Pi.

I am currently testing with a Huawei usb stick, and it's not working stable. The Pi reboots without any trail in the logfiles.

The TP1 - TP2 voltage is 4.98V, so I assume that's not the problem. I will try a self powered hub to see if it works better with it.

You can find the Siemens manual with the AT commands on the web.

External 3g modems like that Siemens usually need an extra 12V supply. An usb 3g can work without it.

Mine shows up as 3 serial ports and a cd rom device with the windows drivers. Some usb device wait for a command like an eject and only switch from cd rom mode to modem mode afterwards.

RE: RPi + GSM/3G module + SIM card

shabaz — Mon, 25 Feb 2013 16:56:15 GMT

To be honest, even with no 3G, GPRS may be a better option. SMS should be absolute last case (at least for M2M). I suppose it does depend on billing options etc but I'm no expert on that unfortunately :-(

RE: RPi + GSM/3G module + SIM card

Former Member — Mon, 25 Feb 2013 16:51:43 GMT

Thank you very much.

Although I was trying to avoid the Arduino, it may prove to be the easiet starting point for me, at least from the learning point of view.

That Sierra module you shown me seems pretty capable, and it's probably worth those 60 pounds + VAT, since it looks like it does a bunch of useful things.

To give you a hint about why I prefer SMS over IP / 3G wireless, the main reason is, as you partially pointed out, 3G coverage and 3G provider reliability. I could use the GoogleMarket over 3G, for example, but that's not exactly the purpose of my project. Another reason is the easy billing: my app is (hopefully ) ment to be used by a paying user, and I can't assume he is smart or that has a smartphone. So a contract with a phone company solves the problem of receiving payments for micro-transactions via SMS (although their cut of my profit would be rather big).

Anyway... thanks for the advice, I hope I can put it to good use soon

Best regards!

PS: I am still open to suggestions from other users, maybe there are also other solutions to chose from.

RE: RPi + GSM/3G module + SIM card

shabaz — Mon, 25 Feb 2013 16:35:15 GMT

I believe most GSM modules just rely on normal AT commands (perhaps an extension). For example, see here which

explains the commands required to send an SMS for one device.

Personally to me it just doesn't make sense these days - M2M is increasingly IP for good reason.

You could try to find a module with a serial interface, and use that since the Raspberry Pi has a serial interface.

You could check out something like this module (I did not read the datasheet).

RE: RPi + GSM/3G module + SIM card

Former Member — Mon, 25 Feb 2013 15:58:23 GMT

I agree with you, a 3G USB stick is definitely a cheaper solution, but it is not the object of my project.

The 3G solution (which is actually basic networking) will be integrated anyway, for testing purposes, until the SMS module is complete.

However, you can still add some value to your reply

Do you have any idea what hardware should I use for SMS ? Also, can you by any chance point to me any tutorials for SMS receiving/sending ?

RE: RPi + GSM/3G module + SIM card

shabaz — Mon, 25 Feb 2013 15:40:58 GMT

SMS is really dated. An alternative method would be to use a 3G USB stick, and just use IP.

If you're in an area with no 3G, then perhaps SMS is a better alternative.