Rotary Dial Becomes USB Keyboard

[Max] had a rotary dial from an old telephone and — unsurprisingly — had nothing in particular to do with it. The simple answer? Use an Arduino Leonardo to turn it into a USB keyboard device.

Of course, the Leonardo can easily impersonate a USB keyboard, so that’s the easy part of the project. Interfacing to the dial requires an understanding of how the phone system works.

While today, TouchTone phones are most common, they were quite uncommon for many years. Early phones required you to have an operator connect your circuit to another person’s circuit. Unfortunately for the operators, the system was inherently unscalable and also cost prohibitive.

There were a variety of schemes tried and — supposedly — an undertaker who was angry that the operator was connecting his customers to her husband’s competing mortuary invented the dial telephone.

The details are pretty simple. A typical dial has two contacts. There’s a normally open contact that closes when you spin the dial to any position. It says closed until the spring returns the dial to the home position.

The other contact is normally closed and makes or breaks the phone line. Each time the dial rewinds past a position, the contact opens briefly. Of course, this is a mechanical system, so the software has to debounce the inputs, but that’s easy enough.

If you don’t have access to a dial, you could always print one. Sort of.

A Conference Badge Breathes Life Into A Rotary Phone

We have covered the astonishing diversity of conference badges to a great extent over the years, and we are always pleased and surprised at the creativity and ingenuity that goes into their creation. But the saddest thing about so many badges is that after the event they go into the drawer and are never touched again, such a missed opportunity!

It’s a trend that [Dan] has reversed though, with his rotary dial phone brought to life with an EMF Tilda MkIV. This was the badge from last year’s EMF Camp 2018, and its defining feature was a built-in GSM mobile phone. We didn’t give it a full review at the time because it has problems with the GSM part at the event and it would have been unfair to display what was an amazing badge in a negative light, but once we got it home it was straightforward enough to put a commercial SIM in the slot and use the public networks with it.

[Dan]’s phone is an Eastern European model that came to him through his grandfather. Inside it’s a relatively conventional design, into which he’s patched a couple of the Tilda’s I/O lines from the dial through a debounce circuit. But simply selecting a couple of lines wasn’t enough, as most of those on its expansion port come via a port expander. He needed inputs that could generate an interrupt, so he hijacked a couple from the on-board joystick. He’s included Python code which you can see in action in the video below. It’s important to note that he’s yet to hook up the audio to the badge so this is a work in progress, but it’s an interesting project nevertheless.

Rotary phones hold a special place among hardware hackers, we’ve featured many projects including them. This isn’t the first GSM rotary phone we’ve brought you, and don’t forget they can also talk via Bluetooth.

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Braille Keyboard Finds Its Voice

If you have a serious visual impairment, using a computer isn’t easy. [Dhiraj] has a project that allows people fluent in Braille to use that language for input. In addition to having a set position for fingers, the device also reads the key pressed as you type. With some third party software it is possible to even create Word documents, according to [Dhiraj].

You can see the finished product in the video below. This is one of those projects where the idea is the hardest part. Reading six buttons and converting them into characters is fairly simple. Each Braille character uses a cell of six bumps and the buttons mimic those bumps (although laid out for your fingers).

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Hack My House: ZoneMinder’s Keeping An Eye On The Place

Hacks are often born out of unfortunate circumstances. My unfortunate circumstance was a robbery– the back door of the remodel was kicked in, and a generator was carted off. Once the police report was filed and the door screwed shut, it was time to order cameras. Oh, and record the models and serial numbers of all my tools.

We’re going to use Power over Ethernet (POE) network cameras and a ZoneMinder install. ZoneMinder has a network trigger capability, and we’ll wire some magnetic switches to our network of PXE booting Pis, using those to inform the Zoneminder server of door opening events. Beyond that, many newer cameras support the Open Network Video Interface Forum (ONVIF) protocol and can do onboard motion detection. We’ll use the same script, running on the Pi, to forward those events as well.

Many of you have pointed out that Zoneminder isn’t the only option for open source camera management. MotionEyeOS, Pikrellcam, and Shinobi are all valid options.  I’m most familiar with Zoneminder, even interviewing them on FLOSS Weekly, so that’s what I’m using.  Perhaps at some point we can revisit this decision, and compare the existing video surveillance systems.

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Video Review: AND!XOR DEF CON 26 Badge

The AND!XOR team have somehow managed to outdo themselves once again this year. Their newest unofficial hardware badge for DEF CON 26 just arrived. It’s a delightful creation in hardware, software, and the interactive challenges built into both.

They call this the “Wild West of IoT”, a name that draws from the aesthetic as well as the badge-to-badge communications features. Built on the ESP32-WROVER module which brings both WiFi and Bluetooth to the party, the badges are designed to form a wireless botnet at the conference. Anyone with a badge can work to advance their level and take more and more control of the botnet as they do.

Check out the video overview and then join me below for a deeper dive into all this badge has to offer.

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State Your Intentions More Clearly With State Machines

To the uninitiated the words ‘State machine’ sound like something scarily big and complex. They aren’t (necessarily) and can be quite useful. In fact, state machines are no physical machines but a model of processes. They link the states a system can be in with allowed transitions. For example a media player when stopped can change to play or open another file. While playing, it can go to pause, stop, reverse, fast forward and so on. A state machine creates a map of all states and how they are connected. It is an abstract tool hat offers a graphical approach to organizing your code before actually programming.

In his video [Chris Guichet] uses a state machine to debounce a switch for a beginner friendly introduction of the concept. He then shows how to turn the hand drawn map to actual code, including a section on debugging state machines.

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Roll Your Own Rotary Encoders

[miroslavus] hasn’t had much luck with rotary encoders. The parts he has tested from the usual sources have all been problematic either mechanically or electrically, resulting in poor performance in his projects. Even attempts to deal with the deficiencies in software didn’t help, so he did what any red-blooded hacker would do — he built his own rotary encoder from microswitches and 3D-printed parts.

[miroslavus]’s “encoder” isn’t a quadrature encoder in the classic sense. It has two switches and only one of them fires when it turns a given direction, one for clockwise and one for counterclockwise. The knob has a ratchet wheel on the underside that engages with a small trip lever, and carefully located microswitches are actuated repeatedly as the ratchet wheel moves the trip lever. The action is smooth but satisfyingly clicky. Personally, we’d forsake the 3D-printed baseplate in favor of a custom PCB with debouncing circuitry, and perhaps relocate the switches so they’re under the knob for a more compact form factor. That and the addition of another switch on the shaft’s axis to register knob pushes, and you’ve got a perfectly respectable input device for navigating menus.

We think this is great, but perhaps your project really needs a legitimate rotary encoder. In that case, you’ll want to catch up on basics like Gray codes.

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