modem

62 Articles

33C3: Dissecting 3G/4G Phone Modems

February 20, 2017 by 21 Comments

[LaForge] and [Holger] have been hacking around on cell phones for quite a while now, and this led to them working on the open cellphone at OpenMoko and developing the OsmocomBB GSM SDR software. Now, they are turning their sights on 3G and 4G modems, mostly because they would like to use them inside their own devices, but would also like to make them accessible to the broader hacker community. In this talk at the 33rd Chaos Communications Congress (33C3), they discuss their progress in making this darkest part of the modern smartphone useful for the rest of us.

This talk isn’t about the plug-and-play usage of a modern cell-phone modem, though, it’s about reprogramming it. They pick a Qualcomm chipset because it has a useful DIAG protocol, and in particular choose the Quectel EC20 modem that’s used in the iPhone5, because it makes the DIAG stream easily available.

Our story begins with a firmware upgrade from the manufacturer. They unzipped the files, and were pleasantly surprised to find that it’s actually running Linux, undocumented and without the source code being available. Now, [LaForge] just happens to be the founder of gpl-violations.org and knows a thing or two about getting code from vendors who use Linux without following the terms and conditions. The legal story is long and convoluted, and still ongoing, but they got a lot of code from Quectel, and it looks like they’re trying to make good.

Qualcomm, on the other hand, makes the Linux kernel source code available, if not documented. (This is the source on which Quectel’s code is based.) [LaForge] took over the task of documenting it, and then developing some tools for it — there is more going on than we can cover. All of the results of their work are available on the wiki site, if you’re getting ready to dig in.

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This Quick Hack Will Keep You Online During Your Next Power Outage

November 28, 2016 by 56 Comments

The modern human’s worst nightmare: a power outage. Left without cat memes, Netflix, and — of course — Hackaday, there’s little to do except participate in the temporary anarchy that occurs when left without internet access. Lamenting over expensive and bulky uninterruptible power supplies, Youtube user [Gadget Addict] hacked together a UPS power bank that might just stave off the collapse of order in your household.

This simple and functional hack really amounts to snipping the end off of a USB  power cable. The cable is then attached to a screw terminal to barrel connector adapter and plugged it into a pass-through power USB power bank. No, really — that’s all there is to it. [Gadget Addict] notes that while most modems and routers are designed to run off a 12V power supply, they still operate at 5V. He goes on to connect several router and router/modem combination units to the power bank. In each case the system appears to boot up and perform normally.

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Bringing A Teletype Into The 21st Century

July 3, 2016 by 9 Comments

Before modern CRTs with ancient VGA connectors, and before fancy video terminals, the display for computers large and slightly smaller was the Teletype. While many of these Teletypes were connected directly, they were designed to be a remote terminal, connected through Ma Bell’s network. [NeXT] over on the Vintage Computer Forums is bringing the iconic ASR33 Teletype into the 21st century by giving this old display a modern way to connect to the outside world.

If you ever see a Teletype in action, it will be connected to a local machine. This was certainly not always the case. The Teletype was designed to connect to remote systems. [NeXT]’s Teletype came with a Call Control Unit designed for Telex lines, which do not exist anymore. Modems for the ASR33 existed, but good luck finding one. Lucky for [NeXT], nearly every modem ever made is backwards-compatible with the Bell Dataphone, one of the standard ways of plugging a Teletype into a phone line. All [NeXT] had to do was put a modem inside this Teletype.

With relays, transistors, LEDs, and a lot of perfboard, [NeXT] successfully built a circuit that would interface the Teletype’s Call Control Unit to a Hayes Smartmodem tucked away inside the stand. Believe it or not, this is an exceptionally useful build; if you ever find a Teletype tucked away in the back of an old office, in a surplus shop, or on Craigslist, odds are it won’t be compatible with any modern electronics. That’s not to say land lines are particularly modern, but since there’s a microcontroller included in the new circuitry, it’s relatively easy to add a USB port to this ancient terminal.

Free Cell Data Transfer With Slowest Morse Code Ever

January 6, 2016 by 41 Comments

Readers of a certain age will remember the payphone trick of letting the phone ring once and then hanging up to get your quarter back. This technique was used with a pre-planned call time to let someone know you made it or you were okay without accruing the cost of a telephone call. As long as nobody answered you didn’t have to pay for the call, and that continues to be the case with some pay-per-minute cellphone plans.

This is the concept behind [Antonio Ospite’s] ringtone data transfer project called SaveMySugar. Don’t judge him, this work has been ongoing for around ten years and started back when cellphone minutes were a concern. We’re just excited to see that he got the excruciatingly slow thing to work.

Those wanting to dig down to the nitty-gritty of the protocol (and you should be one of them) will want to read through the main project page. The system works by dialing the cellphone, letting it ring once, then hanging up. The time between redials determines a Morse code dot, dash, or separation between characters. Because you can’t precisely determine how long it will take each connection to read, [Antonio] built ‘noise’ measurement into the system to normalize variations. The resulting data transfer works quite well. He was able to transfer the word “CODEX” in just six minutes and thirty seconds. But it is automatic, so what do you care? See the edge-of-your-seat-action play out in the video below.

If you can’t stomach that baud, here’s a faster Morse code data transmitter but it doesn’t use the phone.

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Giving The C64 A WiFi Modem

December 21, 2015 by 21 Comments

If there’s any indication of the Commodore 64’s longevity, it’s the number of peripherals and add-ons that are still being designed and built. Right now, you can add an SD card to a C64, a technology that was introduced sixteen years after the release of the Commodore 64. Thanks to [Leif Bloomquist], you can also add WiFi to the most cherished of the home computers.

[Leif]’s WiFi modem for the C64 is made of two major components. The first is a Microview OLED display that allows the user to add SSIDs, passwords, and configure the network over USB. The second large module is the a Roving Networks ‘WiFly’ adapter. It’s a WiFi adapter that uses the familiar Xbee pinout, making this not just a WiFi adapter for the C64, but an adapter for just about every wireless networking protocol out there.

[Leif] introduced this WiFi modem for the C64 at the World of Commodore earlier this month in Toronto. There, it garnered a lot of attention from the Commodore aficionados and one was able to do a video review of the hardware. You can check out [Alterus] loading up a BBS over Wifi in the video below.

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Robot Listens To Commands–Literally

December 10, 2015 by 14 Comments

Where you might see a can, [Adam Kumpf] sees a robot. [Adam’s] robot (named [Canny]) doesn’t move around, but it does have expressive eyebrows, multicolored eyes, and a speaker for a mouth. What makes it interesting, though, is the fact that it receives audio commands via the headphones it wears. You can see [Canny] in action in the video below.

The headphones couple audio tones to [Canny’s] microphone using AFSK (audio frequency shift keying). [Canny] uses an opamp to bring the microphone level up and then uses a 567 PLL IC to decode the audio tones. [Adam] selected two clever frequencies for the mark and space (12345 Hz and 9876 Hz). In addition to being numerically entertaining, the frequencies are far enough apart to be easy to detect, pass through the headphones with no problem, and are not harmonically related.

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Serial Data From The Web To An Arduino

October 10, 2015 by 8 Comments

In the old days, a serial port often connected to an acoustic coupler that gripped a phone handset and allowed a remote connection to a far away serial port (via another phone and acoustic coupler) at a blistering 300 baud or less. The acoustic coupler would do the job of converting serial data to audio and reconstituting it after its trip through the phone lines. Modems advanced, but have mostly given way to DSL, Cable, Fiber, and other high speed networking options.

In a decidedly retro move, [James Halliday] and [jerky] put a modern spin on that old idea. They used the webaudio API to send serial data to a remote Arduino. The hack uses a FET, a capacitor, and a few resistors. They didn’t quite build a real modem with the audio. Instead, they basically spoof the audio port into sending serial data and recover it with the external circuitry. They also only implement serial sending (so the Arduino receives) so far, although they mention the next step would be to build the other side of the connection.

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