GSM modem means wireless serial connections

By now, most of us have seen have seen one of those GSM to wi-fi hotspot bridges. They’re interesting devices, and being able to carry a small wireless router with you at all times is very handy. Surprisingly, we haven’t seen many builds featuring these portable wireless hotspots, something probably due to the effort in breaking out a serial connection on these devices. The people at Open Electronics decided to build their own small serial-enabled cell phone modem, a boon to someone wanting a serial connection to any place with a cell tower.

The Open Electronics GSM/GPRS/GPS modem includes a header for an FTDI USB serial chip and a GSM module. Plug one into your computer and after a few short commands into a terminal, you’ve got a serial connection to nearly anywhere in the world.

The cost of the setup is a little high – around 80€ or $100 USD – and you probably should buy more than one so you can also receive data. While it is more expensive than the XBee wireless boards we see often, this GSM modem isn’t limited to the 300 foot range of the XBee. We’ll probably see this in a high altitude balloon before too long.

Comments

  1. Zee says:

    Why can I buy a 10 euro phone to use with prepaid cards but a GSM serial module is always 80+ euros?

    • Elias says:

      That is a very valid question for sure. One would think that the hw can be gotten quite cheap if there is so much mass production but something seems to differ.

      • Dax says:

        The fact that the phones are subsidized and the price of the phone is pulled out through the contract with inflated prices.

        The only reason the up-front cost is €10 is because people would think twice about buying it.

  2. Matt says:

    Seems not so useful without a web connection. Unless you’re truly in the middle of nowhere, with no internet connection, but you have a cell signal?

    Personally, I’d rather rig up an APRS telemetry device. At least then I can operate even without a cell tower (and could bridge to the internet if I wanted to).

  3. AlexD says:

    The prepaid cell phones are mass produced. Also the future phone card purchases make the original handset cheaper. The gsm serial device isn’t in a high demand and doesn’t have a large market Yet, also the gsm serial device doesn’t make any more money (phone cards)

  4. mojo-chan says:

    Watch out for the current requirements of GSM modems. 2A for a couple of hundred ms isn’t unusual.

  5. Jarel says:

    @zee

    Two things: economies of scale and the fact that even prepaid phones are usually sold at a loss.

  6. jsngrimm says:

    sounds like something the pirate bay could use for their “flying servers” idea. could be used to send info to a central location over serial connection

  7. plaguewolf says:

    I demand a GSM enabled autonomous quad-copter!

  8. Addidis says:

    This is exactly what I was thinking of to make my friend (beer delivery guy) a web enabled AC even though he refuses to get internet. It would be sweet to set it up to respond to texts.

  9. Cyberteque says:

    this looks great, but I’m wondering where the “300′ for an XBee connection” comes from?

    I’ve been getting nearly 1km!

    My main issue is the wireless video is swamping the XBee, going to 900Mhz next!

  10. NewCommentor1283 says:

    im still going to stick with my low cost solution
    EDIT: short distance solution

    (free) cordless ANALOGE telephone plus 2 * 300 baud modems made from ATMegas.

    total parts cost = 5$*2=10$ (atmegas) + 0$ (cordless phone /w no battery) == 10$

    could even use 2 * external PC modem operating at the max “true analog full duplex” mode of 34.3kbps, and that SHOULD be free also

    so a parts cost of free + free + free == freefreefree

    and of course 2 times the equipment == 2 times the overall thouroput

    • NewCommentor1283 says:

      PS: lol 80 or more bucks for a toy/accessory/gadget

      PLUS the actual robot your controlling

    • Jared says:

      How do you go about wiring this up? And getting the modems to talk to each other? I’ve been looking for a way to do something like this just as something to play around with. Would be more interesting if you could use off-the-shelf 56K serial modems.

      • Daniel says:

        Did this years ago… a telephone transformer (1:1, IIRC) allows you to couple into both the speaker and MIC on the cordless handset, and a few AT commands will instruct the modems to talk…

        ATXD on the ‘calling’ modem, ATA on the ‘answering’ modem

  11. Hal says:

    As someone that is using a commercial version of this you are either going to have to go with a data plan or try and get on a M2M provider. Both are going to be costly but an M2M (Machine 2 Machine), such as Kore Telematics, can be cheaper if you are doing very small data. Oh and this is about the same cost as the modem we are using.

  12. rasz says:

    >80€ or $100 USD

    or Free for old Ericsson T10 from the bottom of a drawer

  13. webbr23 says:

    High altitude balloon use will be pretty disappointing. Very little RF energy radiates upwards from GSM base stations. In fact the anteanae are optimised to radiate as much of the signal to where it needed – at ground level. Even tall buildings are without decent coverage until the an antenna is aimed at the building.

    • n0lkk says:

      True even land mobile base/repeater antenna installations often are designed to have a down tilt in the pattern. However at higher altitudes because of the Earth’s curvature may be looking into some distant cell phone towers, the the question becomes if the distance is too great so signal levels are inadequate. An interesting paper exercise to do sometime I guess.

  14. n0lkk says:

    No doubt there are those who can’t be bothered becoming licensed are surely all ready using packet radio for high altitude balloon telemetry and are equally less likely to spend this kind of money be on the lawful side of things. Those who know what they are doing, and can build a clean transmitter run little risk of getting caught, even though the foot print can be pretty big. Not that I’m recommending anyone do so.

  15. conundrum says:

    Fair enough @n0lkk
    I already came up with a workaround for licensing, use light.
    No restrictions on that, apart from you have to ensure it is safe for eyes ie defocussed.
    IIRC the standard says it has to be under 0.8mW in an 8mm diameter beam to be classed as “eye safe”.
    Which means most commercial LED torches are actually dangerous if you stare into the beam!

    A little tip, optical laser mice use a 1mA 0.7mW VCSEL which puts out a nice beam that is ideal for tracking etc. See notes above..

    • n0lkk says:

      An inserting idea, but wouldn’t that be a small footprint on the Earth surface, that would be doing didos as the payload swings on the tether? Could be hell for the recovery teams to keep track of the balloons position. Many of these flights carry student payloads, who would want to receive their telemetry without having to chase down the footprint. Then there’s attenuation by water vapor. RF provides a back up means of tracking if something happens to the GPS telemetry.

  16. Drone says:

    Embedded GSM modems, even older GPRS types are outrageously expensive. Then there’s the whole data plan issue…

    Cellular data plans are capped at notoriously low levels and cost way too much for anything but a trickling flow of data. Exceed the cap – and they hook a vacuum cleaner to your wallet and turn it on!

    Finally, you either have to pay a monthly recurring subscription fee, or constantly recharge a pre-paid SIM card. With the pre-paid cards, typically you lose your number if you don’t recharge the card regularly, whether you need to or not. With the pre-paid cards, your credits often expire if not used withing a certain time window (money lost forever).

    The whole greedy data-plan marketing and business model used by the cellular operators has made me swear-off using them – ever!

  17. jamalailama says:

    @drone
    I’m witchu man

    Anyways…as nifty and fun it may feel to enable devices to communicate together wirelessly….or any ingenious intuitive invention or collaboration for that matter… I think we as humans needa re evaluate what we do with our time. I dunno tho I’m tired as fuck.

    I do think this is badass with gobs o potential

    lol nvm I dunno where I’m going w this

  18. conundrum says:

    Simple way around the prepay problem is to have it automatically send one SMS per week (or whatever the requirement is) via a timer.
    Also the ones available here usually tell you when you dial the topup number when the credit is due to expire.

    Also, another way around the data cap. Encode the data using high compression, as the cap is per MB *sent* not per MB uncompressed.
    This is used on some PCs to get around SATA latency and SSD limitations.
    You take a performance hit but for most applications such as sending video frames its a small price to pay for less $ spent.

  19. stblassitude says:

    OpenWrt, a cheap router (TP-Link TL-WR3220) and a cheap USB UMTS stick seems a good alternative: you gain all capabilities from having a full-blown computer, you can connect more or less anything that has a USB port, plus it doubles as a WiFi base station or client. Purchase price is the same or less, but you need to shop around for a good data deal. At least in Europe, you can find pre-paid and post paid contracts with short terms that cost only a few Euros a month and include a small amount of data (up to 100 MB) for free; plenty if all you want to do is access a serial device every once in a while. Only drawback is the power requirements.

  20. Kyle Hotchkiss says:

    I’d rather just use the spot hack I just saw. Gsm only goes so high!

  21. Jason says:

    Here is a GSM/GPRS / Arduino development board I’ve been playing with recently. It’s an Arduino board with a GSM radio built in. It’s useful for projects that you want to control via SMS message, or you want it to send you messages when a sensor reads a value.

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