Automatic Phone Dialer Illuminates Inner Workings

The invention of the transistor ushered in a lot of technologies that we now take for granted, and one of the less-thought-about areas that it improved living conditions worldwide was by making the touch-tone phone possible. No longer would the world have to fuss with dials to make phone calls, they could simply push some buttons. This technology is still in use today, and it is possible to build external phone dialers that use these tones to make phone calls, as [SunFounder] demonstrates with his latest project.

The tones that a phone makes when a button is pressed correlate with specific frequencies for each number. Automatic dialers like this one help when there are multiple carriers (like different long-distance carriers, for example) where different prefixes can be used to make calls cheaper depending on the destination of the call. A preprogrammed dialer can take all of this complication out of making phone calls. [SunFounder] is able to make a simple dialer from scratch, using an Arduino, its “tone” library, and a speaker that is simply held up to the phone that the call will be placed on.

[SunFounder] points out that he built this more because he’s interested in the inner workings of phones, and not because he needed a purpose-built dialer. It’s a good demonstration of how phones continue to use DTMF though, and how easy it is to interface with such a system. It might also suit a beginner as an introduction to the world of phreaking.

Huge Functionality, Small Package: A Custom Tablet, Raspberry Style

As the adage goes, “if you want something done right, do it yourself.” Desirous of a tablet but preferring to eschew consumer models, [Stefan Vorkoetter] constructed his own compact and lightweight Raspberry Pi tablet, covering several extra miles in the process.

The tablet makes use of a Raspberry Pi 3 and the official touchscreen, with the final product marginally larger than the screen itself. Designed with a ‘slimmer the better’ profile in mind, [Vorkoetter] had to modify several components to fit this precept; most obvious of these are the removal of the Pi’s GPIO headers, USB, and Ethernet ports, and removing the USB power out port from the touchscreen controller board so the two could be mounted side-by-side.

An Adafruit PowerBoost 1000C handles charging the 6200 mAh battery — meaning up to six hours(!) of YouTube videos — via a micro USB, but only after [Vorkoetter] attached a pair of home-made heatsinks due to negligible air flow within the case. A modified USB audio adapter boosts the Pi’s audio capabilities, enabling the use of headphones, a mic, and a built-in speaker which is attached to the tablet’s back cover.

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Game Gear HDMI with SNES Controller

With its backlit color screen and Master System compatibility, the Game Gear was years ahead of its main competition. The major downside was that it tore through alkaline batteries quickly, and for that reason the cheaper but less equipped Game Boy was still able to compete. Since we live in the future, however, the Game Gear has received new life with many modifications that address its shortcomings, including this latest one that adds an HDMI output.

The core of the build is an FPGA which is used to handle pixel decoding and also handles the HDMI output. The FPGA allows for a speed high enough to handle all the data that is required, although [Stephen] still has to iron out some screen-filling issues, add sound over HDMI, and take care of a few various pixel glitches. To turn this hack into a complete hodgepodge of adapters, though, [Stephen] has also added an SNES controller adapter to the Game Gear as well. Nintendo has featured Sonic in many of its games, so although we may have disagreed back in the early 90s we think that this Sega/Nintendo pairing is not crossing any boundaries anymore.

Game Gears have had their share of other modifications as well to make them more capable as a handheld system than they were when they were new. We’ve also seen them turned into a console system (they were Master System compatible, after all) and converted into other things entirely, too.

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Play it Again, Arduino

[MrRedBeard] wanted to play a particular song from an Arduino program and got tired of trying to hand transcribe the notes. A little research turned up that there was a project to convert Music XML (MXL) files to the Arduino. However, [MrRedBeard] wasn’t a fan of the language it used, so he created his own means of doing the same thing. He learned a lot along the way and was willing to share it in a tutorial that will help you if you want to do the same thing. You can see a video of his results, below.

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Virtual CPU Stays on Script

Some will see it as a great thing, and others as an example of how JavaScript is being abused daily, but [Francis Stokes] decided to design his own CPU architecture and implemented a virtual version of it using JavaScript. The CPU is a 16-bit affair and has a simplified assembly language. The code is on GitHub, but the real value is [Francis’] exposition of the design in the original post.

While discussing the design, [Francis] reveals his first pass at the instruction set, discussed what he found wrong about it, and then reveals the final set composed of real instructions and some macros to handle other common cases.

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Control The Volume

For anyone who has owned a boombox or an old(er) cassette player, the digital age volume controls feel incredibly awkward. Keep pressing buttons to get the volume just right can get tiresome real quick. The volume knob just makes sense and in a simple project, [Jeremy S Cook] brings us the Custom Computer Volume Control Knob.

The build employs an Adafruit Trinket board coupled with a rotary encoder and a push button as described by the designers themselves. We reached out to [Jeremy S Cook] to enquire about the build and it turns out his version uses an MDF enclosure as well as an MDF knob. A larger PCB has the encoder and button solder on with the Trinket board connecting to them via multi strand wires. An Acrylic sheet cut to the size serves as the top cover and completes the build.

The button serves as a play/pause button and can come in handy. Since the device enumerates as an HMI device, it should work with almost any OS. It could easily be extended to work with Android Tablets or even iPads. Check out the video below for a demonstration and if you like the idea of custom input devices, check out this DIY shortcut Keyboard. Continue reading “Control The Volume”

Hackaday Prize Entry: Open Source Patient Monitor

Vital sign monitors are usually found in developed countries; they just cost too much for less affluent communities to afford. The HealthyPi project aims to change that by developing an inexpensive but accurate monitor using a Raspberry Pi, a custom hat studded with sensors, and a touch screen. The resulting monitor could be used by medical professionals as well as students and private researchers.

[Ashwin K Whitchurch] and his team created HealthyPi, a Raspberry Pi hat that includes an AFE4490 chip serving as the pulse oximeter front end, an analog to digital converter that interprets the ECG and respiration data, and a MAX30205 body temperature sensor. The hat has its own microcontroller, a ATSAMD21 Cortex M0+ that can also be loaded with the Arduino Zero bootloader.

This project is capable of monitoring a patient’s pulse, respiration, body temperature, and all the other vital signs made measure d by other ‘medical-grade’ vital sign monitors at a fraction of the cost. It’s a democratizing technology, and [Ashwin] already has some working hardware available on Crowd Supply.

Learn more about HealthyPi at the project page or download the code from GitHub.

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