Transmitting HD Video From A Raspberry Pi

March 28, 2015 by Brian Benchoff 30 Comments

It’s been a few years since the RTL-SDR TV Tuner dongle blew up the world of amateur radio; it’s a simple device that listens in on digital television frequencies, but it’s one of those tools that’s just capable enough to have a lot of fun. Now, we have a transmitting dongle. It’s only being used to transmit live HDTV from a Pi, but that in itself is very interesting and opens up a lot of possible builds.

The key piece of hardware for this build is a UT-100C DVB-T modulator. It’s a $169 USB dongle capable of transmitting between 1200-1350 MHz, and with a special edition of OpenCaster it’s possible to transmit over-the-air TV. There’s no amplifier, so you won’t be sending TV very far, but it does work.

On the Raspberry Pi side of the build, the standard camera captures H.264 video with raspivid, which is converted to a DVB compliant stream using ffmpeg. These are well-worn bits of software in the Raspberry Pi world, and OpenCaster takes care of the rest.

While this seems like the perfect solution to completely overbuilt quadcopters, keep in mind transmitting on the 23cm band does require a license. Transmitting in the UHF TV bands is a bad idea.

The Pi 2 Means Faster GPIO

March 27, 2015 by Brian Benchoff 67 Comments

The Raspberry Pi is a great machine to learn the ins and outs of blinking pins, but for doing anything that requires blinking pins fast, you’re better off going with a BeagleBone. This has been the conventional wisdom for years now, and now that the updated Raspberry Pi 2 is out, there’s the expectation that you’ll be able to blink a pin faster. The data are here, and yes, you can.

The method of testing was connecting a PicoScope 5444B to a pin on the GPIO pin and toggling between zero and one as fast as possible. The original test wasn’t very encouraging; Python maxed out at around 70 kHz, Ruby was terrible, and only C with the native library was useful for interesting stuff – 22MHz.

Using the same experimental setup, the Raspberry Pi 2 is about 2 to three times faster. The fastest is still the C native library, topping out at just under 42 MHz. Other languages and libraries are much slower, but the RPi.GPIO Python library stukk sees a 2.5x increase.

Hackaday Retro Edition: Remaking The PDP 8/I With A Raspberry Pi

March 26, 2015 by Brian Benchoff 48 Comments

[Oscar] really likes the PDP-8s, with the extremely old school PDP-8/I being his favorite. If you haven’t checked the price on these recently, getting a real PDP-8/I is nigh impossible. However, after assembling a KIM-1 clone kit, an idea struck: what about building a modern PDP-8/I replica that looks like the real thing, but is powered by modern hardware. This would be fairly cheap to build, and has the added bonus of not weighing several hundred pounds.

The PiDP-8 is [Oscar]’s project to replicate the hardware of the 8/I in a modern format. Instead of hundreds of Flip Chips, this PDP-8 is powered by a Raspberry Pi running the SIMH emulator. The 40-pin GPIO connector on the Pi is broken out to 92 LEDs and 26 toggle switches on a large PCB. This setup gets [Oscar] a reasonable facsimile of the PDP-8/I, but he’s also going for looks too. He created an acrylic panel with artwork copied from an original 8/I that mounts to the PCB and gives the entire project that beautiful late 60s / early 70s brown with harvest gold accent color scheme.

Since this emulated PDP-8/I is running on entirely new hardware, it doesn’t make much sense to haul out disk drives as big as a small child, tape drives, and paper tape readers. Instead, [Oscar] is putting everything on USB sticks. It’s a great solution to the problem of moving around files that are a few kilowords in size.

[Oscar] says he’ll be bringing his PiDP to the Vintage Computer Festival East X in Wall, NJ, April 17-19. We’ll be there, and I’ve already offered [Oscar] the use of a VT-100 terminal. If you’re in the area, you should come to this event. It’s guaranteed to be an awesome event and you’re sure to have a great time. Since this is the 50th anniversary of the introduction of the PDP-8, there will be a half-dozen original PDP-8s set up, including a newly refurbished Straight-8 that came out of the RESISTORS.

Oh, if anyone knows how to connect a Pi to a VT100 (technically a 103), leave a note in the comments. Does it need the RTS/CTS?

RaspPi/Keyboard Project Called Kiiboard, Still Pronounced ‘keyboard’

March 21, 2015 by Rich Bremer 24 Comments

[b10nik] wrote in to tell us about a pretty sweet project that he just finished up. It’s a mechanical keyboard with an integrated Raspberry Pi 2 Model B inside.

[b10nik] purchased a new Filco Ninja Majestouch-2 keyboard just for this project. Although it may make some people cringe, the keyboard was immediately taken apart in order to find an open cavity for the Raspberry Pi. Luckily there was space available towards the left rear of the keyboard case.

If you are familiar with the Raspberry Pi 2 Model B, you know that all of the connections are not on the same side of the board. The USB, audio, HDMI and Ethernet jacks were removed from the PCB. The Ethernet port is not needed since this hack uses WiFi, but those those other ports were extended and terminated in a custom 3D printed I/O panel . The stock keyboard case had to be cut to fit the new panel which results in a very clean finished look.

There’s one more trick up this keyboard’s sleeve, it can be used with the internal Raspberry Pi or be used as a standard keyboard. This is done by way of a FSUSB30MUX USB switch IC that completely disconnects the Raspberry Pi from the keyboard’s USB output.

For another RaspPi/Keyboard solution, check out this concept from a few years ago using a Cherry G80-3000 mechanical keyboard.

Convert A Rotary Phone To VOIP Using Raspberry Pi

March 9, 2015 by Theodora Fabio 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]

Reach Out And Touch Someone With WiFi Photo Booth

March 8, 2015 by Will Sweatman 7 Comments

[kitesurfer1404] put together a nice looking vintage photobooth with WiFi capability. He’s using an arduino to monitor the state of the buttons, LED lighting control, seven segment display AND the DSLR camera. He then uses a Raspberry Pi to control imagine processing and to provide scaling and other effects, which can take up to 20 seconds per image. The Pi runs in WiFi Access Point mode, so anyone with a WiFi capable device can connect to the photo booth and view the images.

We’ve seen some interesting twists on photo booths before. But [kitesurfer1404’s] vintage style makes his stand out all on its own. He designed the graphics with Inkscape and printed them on thick paper. He then soaked the graphics in tea for several hours and dried then for several more days to get that nice rustic look.

Be sure to check out [kitesurfer1404’s] site for full details and an assortment of high resolution images of his project.

Using Cheap Displays With The Raspberry Pi

March 5, 2015 by Brian Benchoff 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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