raspberry pi

1649 Articles

DIY Oscilloscope With A Scanning Laser

March 19, 2015 by 20 Comments

If you’ve ever used an old-school analog oscilloscope (an experience everyone should have!) you probably noticed that the trace is simply drawn by a beam that scans across the CRT at a constant rate, creating a straight line when there’s no signal. The input signal simply affects the y-component of the beam, deflecting it into the shape of your waveform. [Steve] wrote in to let us know about his home-built “oscilloscope” that works a lot like a simple analog oscilloscope, albeit with a laser instead of  a CRT.

[Steve]’s scope is built out of a hodgepodge of parts including Lego, an Erector set, LittleBits, and a Kano Computer (based on a Raspberry Pi). The Pi generates a PWM signal that controls the speed of a LittleBits motor. The motor is hooked up to a spinning mirror that sweeps the laser across some graph paper, creating a straight laser line.

After he got his sweep working, [Steve] took a small speaker and mounted a mirror to its cone. Next he mounted the speaker so the laser’s beam hits the mirror on the speaker, the spinning sweep mirror, and finally the graph paper display. The scope’s input signal (in this case, audio from a phone) is fed into the speaker which deflects the laser beam up and down as it is swept across the paper, forming a nice oscilloscope-like trace.

While [Steve]’s scope might not be incredibly usable in most cases, it’s still a great proof of concept and a good way to learn how old oscilloscopes work. Check out the video after the break to see the laser scope in action.

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Convert A Rotary Phone To VOIP Using Raspberry Pi

March 9, 2015 by 19 Comments

There’s something so nostalgic about the rotary phone that makes it a fun thing to hack and modernize. [Voidon] put his skills to the test and converted one to VoIP using a Raspberry Pi. He used the RasPi’s GPIO pins to read pulses from the rotary dial – a functional dial is always a welcome feature in rotary phone hacks. An old USB sound card was perfect for the microphone and handset audio.

As with any build, there were unexpected size issues that needed to be worked around. While the RasPi fit inside the case well, there was no room for the USB power jack or an ethernet cable, let alone a USB power bank for portability. The power bank idea was scrapped. [voidon] soldered the power cord to the RasPi before the polyfuse to preserve the surge protection, used a mini-USB wifi dongle, and soldered a new USB connector to the sound card. [Voidon] also couldn’t get the phone’s original ringer to work, so he used the Raspberry Pi’s internal sound card to play ringtones.

The VoIP (SIP) was managed by some Python scripting, available at GitHub. [voidon] has some experience in using Asterisk at his day job, so it will be interesting to see if he incorporates it in the future.

[via Reddit]

 

 

New Part Day: Really, Really Wide Screens

March 7, 2015 by 70 Comments

Once again my inbox runneth over with press releases, Kickstarter announcements, unsolicited emails, and a bunch of product announcements. Most of these, of course, are never to be seen again. Once in a great while – statistically insignificant, really – there’s a product announcement that’s just interesting enough to take a closer look at. This time, it’s a really, really wide screen.

LCDs are curious beasts when it comes to display interfaces. Back in the bad old days of gigantic tube TVs, the aspect ratio of these displays was fairly limited. You could get a 4:3 display, and with the rare exception of o-scopes, vector displays, and other weird devices, that was it. Since then we’ve moved to LCDs, a promising technology if you want a display in the shape of a car dashboard, or as a thin strip to put on some rackmount modules. It took this long for a sliver of an LCD to appear.

This display produced by EarthLCD is a 10.4 inch display, about ten inches wide and one inch tall. The resolution is 1024 by 100. It is, by far, the skinniest LCD ever produced. The closest you’re going to get to a display with this kind of aspect ratio are old character LCDs, and even then you’re not going to address individual pixels.

If you’re struggling to figure out what this would be used for, this product makes it somewhat obvious. It’s a 1U rack with a beautiful 1024×100 display embedded in the front. You’ve never seen a server that cool.

Interestingly, the 1U display is driven by a single Raspberry Pi, and looking at the datasheet for the display (PDF) tells you pretty much everything. The display is driven by a regular old parallel interface, with six bits of color for R, G, and B. That means it can be driven with a Raspberry Pi without an adapter board, a BeagleBone, or even smaller ARM micros with the obvious reduction in color depth.

While the display isn’t a game changer or something that will knock your socks off, it is, interesting and something that could find its way into some interesting projects. If you have any idea what those projects would be, drop a note in the comments.

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Using Cheap Displays With The Raspberry Pi

March 5, 2015 by 63 Comments

The Raspberry Pi B+ has a native VGA connection. Sure, it’s hidden away in binary blobs and device trees, and you need to wire up the GPIO pins just right, but it’s possible to connect a VGA monitor to a Raspi B+ natively. For the brave, smart, or foolish, this means you can also drive raw DPI displays. [Robert] had a few of these dirt cheap displays sitting around and decided to give the entire thing a go. It worked, and he’s written down how to do it.

One of the chip architects for the Raspberry Pi, [Gert van Loo], was exceedingly clever when designing the Pi. There’s a parallel interface in the chip that, when combined with a few dozen resistors, can drive a VGA display in addition to the HDMI display. Screens with a Display Parallel Interface are actually pretty similar to what the VGA spec calls for. The problem is, hardly any of this is documented for the Raspberry Pi, and finding it means trawling through forums.

[Robert]’s example circuit uses a 5″ display from Adafruit, a 40-pin breakout, and a bunch of prototyping wires. Setup requires grabbing a cut down version of the device tree used for the Raspi VGA breakout board, setting the output format, rgb order, and aspect ratio of the display, and wiring everything up.

What’s interesting here is that [Robert] reproduced this project from scratch, and found that any display with a 40-pin DPI connector will work with the Raspi, provided you have a datasheet. That’s pretty cool; these displays can be cheap, and since we don’t yet have a proper DSI display for the Pi, this will have to do for now.

Video below of [Robert]’s inspiration for this build, [Ladyada].

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RetroPie Turned Game Gear

March 2, 2015 by 12 Comments

Running vintage console emulators on a Raspberry Pi seems to be the thing all the cool kids are doing. The coolest RetroPie builds take a vintage console – usually of the Nintendo genus – stuff a Raspi in there somehow, and Bob’s your uncle. [Phil Herlihy] over at Adafruit is throwing his hat into the ring with a similar build. For this one, though, he’s using Sega’s oft-maligned Game Gear. He might actually get more than a few hours out of the battery with this one, and the battery is rechargeable, too. You can’t beat that.

The build begins with tearing down an old Game Gear, chopping up the PCB to save the button contact, and starting to fit all the components in there. The display is completely replaced with a 3.5″ composite display, a bit larger than the 3.2″ display found in a stock Game Gear. That’s not a problem, there’s a surprising amount of space behind the bezel, and if you’re good enough with an xacto blade and a file, it will look stock.

The rest of the components include an amplifier board, battery charge regulator, a 2500mAh LiPo, and a Teensy to read the buttons. There are a few modifications required for the Pi, but the finished device presents a USB port to the outside world; keep a keyboard by your side, and this is a portable Pi in every respect.

An Upgrade To A Raspberry Pi Media Server

March 1, 2015 by 23 Comments

For the last few years, [Luke] has been running a music server with a Raspberry Pi. With the new Raspberry Pi 2 and its quad core processor, he thought it was time for an upgrade.

The build consists of a Raspi 2, a HiFiBerry Dac to address the complaints of terrible audio on the Pi, an aluminum enclosure, and some electronics for IO and a real software shutdown for the Pi. The Arduino also handles an IR remote and a rotary encoder on the front of the enclosure.

The software is the Logitech Media Server along with Squeezeslave. The front end is custom, though, with functions for shutdown and receiving IR remote codes. Everything is served up by Flask, with a 32GB microSD card stuffed into the Pi to store MP3s. All in all, a great build.

Raspberry Pi GSM Hat

February 28, 2015 by 12 Comments

The Spark Electron was released a few days ago, giving anyone with the Arduino IDE the ability to send data out over a GSM network. Of course, the Electron is just a GSM module tied to a microcontroller, and you can do the same thing with a Pi, some components, and a bit of wire.

The build is fairly basic – just an Adafruit Fona, a 2000 mah LiPo battery, a charge controller, and a fancy Hackaday Perma-Proto Hat, although a piece of perf board would work just as well in the case of the perma-proto board. Connections were as simple as power, ground, TX and RX. With a few libraries, you can access a Pi over the Internet anywhere that has cell service, or send data from the Pi without a WiFi connection.

If you decide to replicate this project, be aware you have an option of soldering the Fona module right side up or upside down. The former gives you pretty blinking LEDs, while the latter allows you to access the SIM. Tough choices, indeed.