Raspberry Pi Remote Audio Link

Hardware for remote audio link


In broadcast, lots of people are still using dedicated analog lines to connect remote sites. These operate like old telephone systems: you call up the operator and request to be patched through to a specific site. They’re also rather expensive.

For a hospital radio station, [Marc] wanted to replace the old system with something less costly. The result is his Raspberry Pi STL in a Box. Inside the box is a Raspberry Pi, PiFace display, a pair of meters, and some analog hardware for the audio.

On the software side, the system uses LiquidSoap to manage the stream. LiquidSoap uses a language to configure streams, and [Marc] has a write-up on how to configure LiquidSoap for this application. On the hardware side, SSM2142 ICs convert the signal from single-ended to balanced. The meters use the LM3915 bar drivers to control the meters.

The Python script that controls the box is provided, and could be helpful for anyone needing to build their own low-cost audio link.


PiFace Control & Display Tear Down


[John’s] currently working on a rather fun PiNoir & Santa Catcher Challenge, and one of the main components is a PiFace Control and Display, which allows you to use a Raspberry Pi without a keyboard or mouse. Curious to see how this module worked, [John] decided to do a tear down and find out!

Using a de-soldering tool he removed the 16×2 LCD which obstructs most of the components on the panel, which revealed a 16 bit SPI port expander from Microchip MCP23S17. He continued to examine components and checked values using a multimeter to come up with the following circuit diagram:

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Frozen Pi — An Affordable Bullet Time Recorder

What happens when you strap 48 Raspberry Pi cameras together with nearly half a kilometer of network cables? You get your own bullet time capture rig.

Originally inspired by the unique film effect of the  Matrix and an old BBC documentary called Supernatural: The Unseen Powers of Animals, the owner of PiFace decided to try re-creating the bullet time effect himself.

To create the rig they’ve taken 48 Raspberry Pis, each with a PiFace controller board and the standard camera. The controller board allows the Raspberry Pi to be used without a keyboard or mouse, so all the network cables have to do is send a simple code to each pi in order to take the pictures. A simple laser cut wood profile is used to snap them all together into a giant ring.

While 48 Raspberry Pis is a lot, they think this is a reasonable project for a classroom environment — besides, how cool would it be to go to school and film your own bullet time stunts?

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Controlling a Raspberry Pi with real life redstone


We’ve seen computers built in Minecraft out of redstone, the game’s version of electricity, circuits, and digital logic. We’ve even seen a few redstone contraptions controlling real-world devices. [Angus]’ build, though, takes things to a whole new level. He’s created a bridge between Minecraft circuits and their real life counterparts using a Raspberry Pi.

[Angus]’ build relies on a mod for Minecraft servers running as a Bukkit plugin. Blocks powered by redstone are labeled with an in-game sign, and messages regarding the state of a block are passed over the network using the MQTT protocol.

The hardware side of the build is a Raspberry Pi with a PiFace expansion board. With this setup, [Angus] can control LEDs on the PiFace by toggling Minecraft levers, or light up redstone lamps using the PiFace’s buttons.

If you’d like to try this out for yourself, you can grab the Bukkit plugin over on [Angus]’s git. Check out the video of the real life redstone in action after the break.

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