Revive that old Analog Cell Phone with SDR

With the latest and greatest 5G cellular networks right around the corner, it can be difficult to believe that it wasn’t so long ago that cell phones relied on analog networks. They aren’t used anymore, but it might only take a visit to a swap meet or flea market to get your hands on some of this vintage hardware. Of course these phones of a bygone era aren’t just impractical due to their monstrous size compared to modern gear, but because analog cell networks have long since gone the way of the floppy disk.

But thanks to the efforts of [Andreas Eversberg] those antique cell phones may live again, even if it’s only within the radius of your local hackerspace. His software allows the user to create a functioning analog base station for several retro phone networks used in Europe and the United States, such as AMPS, TACS, NMT, Radiocom, and C450. You can go the old school route and do it with sound cards and physical radios, or you can fully embrace the 21st century and do it all through a Software Defined Radio (SDR); in either event, calls to the base station and even between multiple mobile devices is possible with relatively inexpensive hardware.

[Andreas] has put together exceptional documentation for this project, which starts with a walk through on how you can setup your DIY cell “tower” with traditional radios. He explains that amateur radios are a viable option for most of the frequencies used, and that he had early success with modifying second-hand taxi radios. He even mentions that the popular BaoFeng handheld radios can be used in a pinch, though not all the protocols will work due to distortion in the radio.

If you want to take the easy way out, [Andreas] also explains how to replace the radios with a single SDR device. This greatly simplifies the installation, and turns a whole bench full of radios and wires into something you can carry around in your pack if you were so inclined. His software has specific options to use the LimeSDR and LimeSDR-Mini, but you should be able to use other devices with a bit of experimentation.

We’ve previously reviewed the LimeSDR-Mini hardware, as well as covered its use in setting up DIY GSM networks.

EMMC Data Recovery From A Bricked Phone

We’ve probably all got at least one old cell phone lurking somewhere around our bench. In most cases they’ll still work, but their  batteries may be exhausted and their OS could be an ancient version. But sometimes there will be a phone that just died. One minute the flagship model, the next a useless slab of plastic and glass with the added annoyance of those priceless photos of Aunty May’s 80th forever locked in its memory.

[Andras Kabai] had just such a device land on his desk, a high-end Sony whose screen had gone blank. Others had tried, he was the last hope for the data it contained. He zoomed in on the eMMC chip on its motherboard, desoldered it and hooked it up via a specialist eMMC reader to recover those files. That was a very simple description of a far more involved process that he sets out in his post about it, a post that is fascinating reading and serves as a handy primer for any reader who might like to try it for themselves. We learn about the MMC interface and how simple it can be in its serial form, how with some fine soldering you can use a cheap USB reader, and that eMMC chips have a pinout conforming to a JEDEC standard.

Finally we see the software side as he takes the various SQLite databases and extracts the data for the user. It shows, all is not necessarily lost, however dead a phone may be.

We’ve seen [Andras] before, using an old scanner in his PCB fab.

Smartphone Mod Goes Out On A Limb

The modern smartphone has a variety of ways to interact with its user – the screen, the speakers, and of course, the vibration motor. But what if your phone could interact physically? It might be unnerving, but it could also be useful – and MobiLimb explores exactly this possibility.

Yes, that’s right – it’s a finger for your mobile phone. MobiLimb has five degrees of freedom, and is built using servomotors which allow both accurate movement as well as positional feedback into the device. Additionally, a touch-sensitive potentiometer is fitted, allowing the robofinger to respond to touch inputs.

The brains behind the show are provided by an Arduino Leonardo Pro Micro, and as is usual on such projects, the mechanical assembly is 3D printed – an excellent choice for producing small, complex parts. Just imagine the difficulty of trying to produce robotic fingers with classic machine tools!

The project video shows many different possibilities for using the MobiLimb – from use as a basic notification device, to allowing the smartphone to crawl along a table. We frankly can’t wait until there’s a fully-functional scorpion chassis to drop an iPhone into – the sky really is the limit here.

Interested in other unique ways to interact with your smartphone? Check out these nifty 3D printed physical buttons.

Old Phone, New Remote Switch

With mobile phones now ubiquitous for the masses in much of the world for over two decades, something a lot of readers will be familiar with is a drawer full of their past devices. Alongside the older smartphone you’ll have a couple of feature phones, and probably at the bottom a Nokia candybar or a Motorola flip phone. There have been various attempts over the years to make use of the computing power the more recent ones contain through using their smartphone operating systems, but the older devices remain relatively useless.

[Vishwasnavada] has a neat plan though, using an ancient phone as a remote trigger device, by interfacing it with an Arduino. There are many ways this could be achieved depending on the model of the phone in question, but one thing common to nearly all devices is a vibration motor. Removing the motor and taking its power line to a GPIO allows the Arduino to sense when the phone is ringing. The idea then is that a call can be placed to the phone which is not picked up, but because it triggers the vibration motor it can be used to make the microcontroller do something remotely. A hack with limited capabilities then, but one that is cheap and simple, uses a recycled device, and should work almost anywhere populated on the planet given the global reach of 2G networks.

This isn’t the first respin of a classic Nokia we’ve brought you, they will also talk data.

A Calculator With 3G Inside

For many of us, a calculator is something we run as an app on our mobile phones. Even the feature phones of a couple of decades ago bundled some form of calculator, so that particular task has joined the inevitable convergence of functions into the one device.

For [Scott Howie] though, a mobile phone is something to run as an app on his calculator. He’s integrated a cellphone module into his TI-84 calculator, and though perhaps it won’t be knocking Apple or Samsung off their pedestals just yet, it’s fully functional and both makes and receives calls.

To perform this feat he’s taken the cellphone module and one of the tiniest of Arduino boards, and fitted them in the space beneath the TI-84’s keyboard by removing as much extraneous plastic as he could. The calculator’s 4 AAA cells could not supply enough power on their own, so he’s supplemented them with a couple more, and replaced the alkaline cells with rechargeables. A concealed switch allows the cellphone to be turned off to preserve battery life.

The calculator talks to the Arduino via a slightly unsightly external serial cable, and all his software is handily available in a GitHub repository. His video showing the whole build in detail is below the break, so if you fancy a calculator with cellular connectivity, here’s your opportunity. Hang on — couldn’t you use a device like this for exam cheating?

Continue reading “A Calculator With 3G Inside”

Emergency Cell Tower on a Budget

Cell phone towers are something we miss when we’re out of range, but imagine how we’d miss them if they had been destroyed by disastrous weather. In such emergencies it is more important than ever to call loved ones, and tell them we’re safe. [Matthew May] and [Brendan Harlow] aimed to make their own secure and open-source cellular network antenna for those occasions. It currently supports calling between connected phones, text messaging, and if the base station has a hard-wired internet connection, users can get online.

This was a senior project for a security class, and it seems that the bulk of their work was in following the best practices set by the Center for Internet Security. They adopted a model intended for the Debian 8 operating system which wasn’t a perfect fit. According to Motherboard their work scored an A+, and we agree with the professors on this one.

Last year, the same SDR board, the bladeRF, was featured in a GSM tower hack with a more sinister edge, and of course Hackaday is rife with SDR projects.

Thank you [Alfredo Garza] for the tip.

Detecting Mobile Phone Transmissions With a Sound Card

Anyone who had a cheap set of computer speakers in the early 2000s has heard it – the rhythmic dit-da-dit-dit of a GSM phone pinging a cell tower once an hour or so. [153armstrong] has a write up on how to capture this on your computer. 

It’s incredibly simple to do – simply plug in a set of headphone to the sound card’s microphone jack, leave a mobile phone nearby, hit record, and wait. The headphone wire acts as an antenna, and when the phone transmits, it induces a current in the wire, which is picked up by the soundcard.

[153armstrong] notes that their setup only seems to pick up signals from 2G phones, likely using GSM. It doesn’t seem to pick up anything from 3G or 4G phones. We’d wager this is due to the difference in the way different cellular technologies transmit – let us know what you think in the comments.

This system is useful as a way to detect a transmitting phone at close range, however due to the limited bandwidth of a computer soundcard, it is in no way capable of actually decoding the transmissions. As far as other experiments go, why not use your soundcard to detect lightning?