modem

65 Articles

A laptop with a desk phone and a 3D-printed acoustic coupler next to it

Acoustic Coupler Gets You Online Through Any Desk Phone

December 30, 2022 by 48 Comments

Up until the mid-1980s, connecting a computer to a phone line was tricky: many phone companies didn’t allow the connection of unlicensed equipment to their network, and even if they did, you might still find yourself blocked by a lack of standardized connectors. A simple workaround for all this was an acoustic coupler, a device that played your modem’s sounds directly into a phone’s receiver without any electrical connection. Modem speeds were slow anyway, so the limited bandwidth inherent in such a system was not much of a problem.

Nowadays it’s easier to find an internet connection than a phone line in many places, but if you’re stuck in an ancient hotel in the middle of nowhere you might just find [GusGorman]’s modern take on the acoustic coupler useful. The basic design is quite simple: it’s a 3D-printed box with two cups that fit a typical phone handset and a space to put a USB speaker and microphone. Thanks to minimodem it’s easy to set up a connection with any other computer equipped with a phone connection.

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ADSL Router As Effects Pedal

September 8, 2022 by 11 Comments

Moore’s law might not be as immutable as we once though thought it was, as chip makers struggle to fit more and more transistors on a given area of silicon. But over the past few decades it’s been surprisingly consistent, with a lot of knock-on effects. As computers get faster, everything else related to them gets faster as well, and the junk drawer tends to fill quickly with various computer peripherals and parts that might be working fine, but just can’t keep up the pace. [Bonsembiante] had an old ADSL router that was well obsolete as a result of these changing times, but instead of tossing it, he turned it into a guitar effects pedal.

The principle behind this build is that the router is essentially a Linux machine, complete with ALSA support. Of course this means flashing a custom firmware which is not the most straightforward task, but once the sound support was added to the device, it was able to interface with a USB sound card. An additional C++ program was created which handles the actual audio received from the guitar and sound card. For this demo, [Bonsembiante] programmed a ring buffer and feeds it back into the output to achieve an echo effect, but presumably any effect or a number of effects could be programmed.

For anyone looking for the source code for the signal processing that the router is now performing, it is listed on a separate GitHub page. If you don’t have this specific model of router laying around in your parts bin, though, there are much more readily-available Linux machines that can get this job done instead.

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Simple Universal Modem Helps Save And Load Data From Tape

July 27, 2022 by 22 Comments

Back in the early days of the home computer revolution, data was commonly saved on tape. Even better, those tapes would make an almighty racket if you played them on a stereo, because the data was stored in an audio format.  The Simple Universal Modem from [Anders Nielsen] is built to work in a similar way, turning data into audio and vice versa.

The project consists of a circuit for modulating data into audio, and demodulating audio back into data. It’s “universal” because [Anders] has designed it to be as format-agnostic as possible. It doesn’t matter whether you want to store data on a digital voice recorder, a cassette deck, or an old reel-to-reel. This build should work fairly well on all of them!

On the modulation side of things, it’s designed to be as analog-friendly as possible. Rather than just spitting out rough square waves, it modulates them into nice smooth sine waves with fewer harmonics. On the demodulation side, it’s got an LM393 comparator which can read data on tape and spit out a clean square wave for easy decoding by digital circuitry.

If you find yourself trying to recover old data off tapes, or writing to them for a retrocomputing project, this build might be just what you need. [Anders] even goes as far as demonstrating its use with an old reel-to-reel deck in a helpful YouTube video.

There really were some weird ways of storing data way back when. Just ask IBM. Video after the break.

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GGWave Sings The Songs Of Your Data

July 6, 2022 by 12 Comments

We’re suckers for alternative data transmission methods, and [Georgi Gerganov]’s ggwave made us smile. At its core, it’s doing what the phone modems of old used to do – sending data encoded as different audio tones. But GGwave does this with sophistication!

It splits the data into four-bit chunks, and uses 16 different frequency offsets to represent each possible value. But for each chunk, these offsets are added to one of six different base frequencies, which allows the receiving computer to tell which chunk it’s in. It’s like a simple framing concept, and it makes the resulting data sound charmingly like R2-D2. (It also uses begin and end markers to be double-sure of the framing.) The data is also sent with error correction, so small hiccups can get repaired automatically.

What really makes ggwave shine is that it’s ported to every platform you care about: ESP32, Arduino, Linux, Mac, Windows, Android, iOS, and anything that’ll run Python or JavaScript. So it’ll run in a browser. There’s even a GUI for playing around with alternative modulation schemes. Pshwew! This makes it easy for a minimalist microcontroller-based beeper button to control your desktop, or vice-versa. An ESP32 makes for an IoT-style WiFi-to-audio bridge. Write code on your cell phone, and you can broadcast it to any listening microcontroller. Whatever your use case, it’s probably covered.

Now the downside. The data rate is slow, around 64-160 bits per second, and the transmission is necessarily beepy-booopy, unless you pitch it up in to the ultrasound or use the radio-frequency HackRF demo. But maybe you want to hear when your devices are talking to each other? Or maybe you just think it’s cute? We do, but we wouldn’t want to have to transmit megabytes this way. But for a simple notification, a few bytes of data, a URL, or some configuration parameters, we can see this being a great software addition to any device that has a speaker and/or microphone.

Oh my god, check out this link from pre-history: a bootloader for the Arduino that runs on the line-in.

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Cable Modem Turned Spectrum Analyzer

August 27, 2021 by 19 Comments

Hopefully by now most of us know better than to rent a modem from an internet service provider. Buying your own and using it is almost always an easy way to save some money, but even then these pieces of equipment won’t last forever. If you’re sitting on an older cable modem and thinking about tossing it in the garbage, there might be a way to repurpose it before it goes to the great workbench in the sky. [kc9umr] has a way of turning these devices into capable spectrum analyzers.

The spectrum analyzer feature is a crucial component of cable modems to help take advantage of the wide piece of spectrum that is available to them on the cable lines. With some of them it’s possible to access this feature directly by pointing a browser at it, but apparently some of them have a patch from the cable companies to limit access. By finding one that hasn’t had this patch applied it’s possible to access the spectrum analyzer, and once [kc9umr] attached some adapters and an antenna to his cable modem he was able to demonstrate it to great effect.

While it’s somewhat down to luck as to whether or not any given modem will grant access to this feature, for the ones that do it seems like a powerful and cheap tool. It’s agnostic to platform, so any computer on the network can access it easily, and compared to an RTL-SDR it has a wider range. There are some limitations, but for the price it can’t be beat which will cost under $50 in parts unless you happen to need two inputs like this analyzer .

Thanks to [Ezra] for the tip!

APRS Implemented At Low Cost And Small Size

June 15, 2021 by 17 Comments

Before smartphones and Internet of Things devices were widely distributed, the Automatic Packet Reporting System (APRS) was the way to send digital information out wirelessly from remote locations. In use since the 80s, it now has an almost hipster “wireless data before it was cool” vibe, complete with plenty of people who use it because it’s interesting, and plenty of others who still need the unique functionality it offers even when compared to more modern wireless data transmission methods. One of those is [Tyler] who shows us how to build an APRS system for a minimum of cost and size.

[Tyler]’s build is called Arrow and operates on the popular 2 metre ham radio band. It’s a Terminal Node Controller (TNC), a sort of ham radio modem, built around an ESP32. The ESP32 handles both the signal processing for the data and also uses its Bluetooth capability to pair to an Android app called APRSDroid. The entire module is only slightly larger than the 18650 battery that powers it, and it can be paired with a computer to send and receive any digital data that you wish using this module as a plug-and-play transceiver.

While the build is still has a few limitations that [Tyler] notes, he hopes that the project will be a way to modernize the APRS protocol using methods for radio transmission that have been improved upon since APRS was first implemented. It should be able to interface easily into any existing ham radio setup, although even small balloon-lofted radio stations can make excellent use of APRS without any extra equipment. Don’t forget that you need a license to operate these in most places, though!

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Hackaday Links: June 13, 2021

June 13, 2021 by 6 Comments

When someone offers to write you a check for $5 billion for your company, it seems like a good idea to take it. But in the world of corporate acquisitions and mergers, that’s not always the case, as Altium proved this week when they rebuffed a A$38.50 per share offer from Autodesk. Altium Ltd., the Australian company whose flagship Altium Designer suite is used by PCB and electronic designers around the world, said that the Autodesk offer “significantly undervalues” Altium, despite the fact that it represents a 42% premium of the company’s share price at the end of last week. Altium’s rejection doesn’t close the door on ha deal with Autodesk, or any other comers who present a better offer, which means that whatever happens, changes are likely in the EDA world soon.

There were reports this week of a massive explosion and fire at a Chinese polysilicon plant — sort of. A number of cell phone videos have popped up on YouTube and elsewhere that purport to show the dramatic events unfolding at a plant in Xinjiang province, with one trade publication for the photovoltaic industry reporting that it happened at the Hoshine Silicon “997 siloxane” packing facility. They further reported that the fire was brought under control after about ten hours of effort by firefighters, and that the cause is under investigation. The odd thing is that we can’t find a single mention of the incident in any of the mainstream media outlets, even five full days after it purportedly happened. We’d have figured the media would have been all over this, and linking it to the ongoing semiconductor shortage, perhaps erroneously since the damage appears to be limited to organic silicone production as opposed to metallic silicon. But the company does supply something like 17% of the world’s supply of silicon metal, so anything that could potentially disrupt that should be pretty big news.

It’s always fun to see “one of our own” take a project from idea to product, and we like to celebrate such successes when they come along. And so it was great to see the battery-free bicycle tire pressure sensor that Hackaday.io user CaptMcAllister has been working on make it to the crowdfunding stage. The sensor is dubbed the PSIcle, and it attaches directly to the valve stem on a bike tire. The 5-gram sensor has an NFC chip, a MEMS pressure sensor, and a loop antenna. The neat thing about this is the injection molding process, which basically pots the electronics in EDPM while leaving a cavity for the air to reach the sensor. The whole thing is powered by the NFC radio in a smartphone, so you just hold your phone up to the sensor to get a reading. Check out the Kickstarter for more details, and congratulations to CaptMcAllister!

We’re saddened to learn of the passing of Dale Heatherington last week. While the name might not ring a bell, the name of his business partner Dennis Hayes probably does, as together they founded Hayes Microcomputer Products, makers of the world’s first modems specifically for the personal computer market. Dale was the technical guru of the partnership, and it’s said that he’s the one who came up with the famous “AT-command set”. Heatherington only stayed with Hayes for seven years or so before taking his a $20 million share of the company and retiring, which of course meant more time and resources to devote to tinkering with everything from ham radio to battle bots. ATH0, Dale.