Transmit FM Using Raspberry Pi And No Additional Hardware

December 10, 2012 by Mike Szczys 75 Comments

Now here’s a project that actually hacks the Rapsberry Pi rather than just using it as an embedded computer. [Londons Explorer] figured out how to turn the RPi into an FM transmitter. For now it’s done entirely in the user space, but we’re sure it could be improved if someone wanted to drill down further into the hardware. For those wanting to give it a try he’s rolled everything into a simple python package.

The technique requires nothing additional except a 20cm wire to serve as an antenna. The trick is to map GPIO pin number 4 to a position in memory. The clock generator is then used to toggle this pin at 100 MHz, which is the frequency to which your radio should be tuned. A fractional divider adjusts the frequency based on the sound file being transmitted.

The proof of concept for this was able to reliably transmit at a distance of about fifty meters through several walls. The problem is that this technique is limited in the amount of data which can be sent. Right now it’s only about 6-bit audio. But descending deeper through the abstraction layers to put DMA (Direct Memory Access) to use may be able to improve upon this.

[Thanks Owen via Reddit]

Frequency Analyzer Built From The New Stellaris Launchpad

September 6, 2012 by Mike Szczys 79 Comments

Here’s the first project we’ve seen for the new Stellaris Launchpad. It’s a frequency analyzer which displays a graph on an 8×8 LED module. What’s that you say? You haven’t received your new Launchpad board yet? Neither have we since they don’t start shipping until the end of the month. But [EuphonistiHack] works as a software dev for TI and snagged one of the early development units.

Hardware is rather simple. He uses an OpAmp to feed audio from his laptop to the ARM processor. The 8×8 LED module is an MSP430 booster pack that is addressed via SPI. On the software side of things he’s really taking advantage of hardware peripherals to simplify his work. A timer triggers each ADC reading which in turn writes the values using uDMA. Digital Signal Processing (available as a CMSIS library for many ARM chips) is then used to translate the ADC value to one that can be displayed on the LEDs. Check out the video after the break to see the final version.

The Hackaday writers are looking for an easier name for this hardware than “Stellaris Launchpad”. It doesn’t seem to lend itself to a shorter name, like RPi or Raspi does for the Raspberry Pi. If you’ve got a catchy nick name for the new board please share it in the comments.

Playing Chess On A Microcontroller

July 6, 2011 by Brian Benchoff 19 Comments

[Arthur Benemann] started a little project for his electrical engineering program, and suffered the worst case of feature creep we’ve ever seen. He just posted an instructable of his picChess project that is able to play chess on a VGA monitor with a keyboard, with sound, a clock, temperature sensor. Apparently, [Arthur] was bored one evening and threw in an implementation of Conway’s game of life.

[Arthur] chose a DSPIC33F μC for his project with everything laid out on a bread board. He’s quite proud of his VGA routine, the first time he’s ever used DMA. We’re really impressed by [Arthur]’s chess engine – his is the first homebrew chess engine we’ve seen on Hack A Day. Although the engine is a brute-force search with Alpha-beta pruning, the engine itself seems fairly advanced that will even supports castling.

Although a few rules aren’t supported and the ELO rating of the engine isn’t known, [Arthur]’s engine should still be able to beat an amateur player. A fairly impressive feat indeed.

Check out [Arthur]’s video after the break.

Continue reading “Playing Chess On A Microcontroller” →

PCjr 25 Years Later

November 8, 2008 by Eliot 24 Comments

pcjr

[Trixter], connoisseur of old hardware, is celebrating the 25th anniversary of the PCjr. IBM’s PCjr was killed only 18th months after being revealed and [Trixter] lays out exactly why. Overall, it was designed to be cheap to produce and sell, but many of the choices made it difficult to use. They used the CPU instead of DMA for floppy access; cheaper to make, but you couldn’t do much during disk reads because of it. The video memory scheme left little room for programs that could take advantage of it. It also had compatibility issues that made IBM clones a more attractive choice. [Trixter] ends by pointing out that some good came of it when the Tandy 1000 copyied the good ideas while leaving out the restrictive memory issues. He recommends Mike’s PCjr Page for more information on this classic machine.