When I saw how easy it looked to do, I ran over to my Pi, downloaded the code, and got it running within a matter of minutes. One of the best parts about this project is that you don’t need much hardware besides the Pi itself. Just connect a 20cm piece of wire to GPIO pin 40 to act as the antenna and then you’re all set.
And from the project description over at the Imperial College Robotics Society wiki:
Below is some code that was hacked together over a few hours at the Code Club pihack. It uses the hardware on the raspberry pi that is actually meant to generate spread-spectrum clock signals on the GPIO pins to output FM Radio energy. This means that all you need to do to turn the Raspberry-Pi into a (ridiculously powerful) FM Transmitter is to plug in a wire as the antenna (as little as 20cm will do) into GPIO pin 4 and run the code posted below. It transmits on 100.0 MHz.
When testing, the signal only started to break up after we went through several conference rooms with heavy walls, at least 50m away, and crouched behind a heavy metal cabinet. The sound quality is ok, but not amazing, as it currently plays some clicks when the CPU gets switched away to do anything else than play the music. The plan was to make a kernel mode driver that would be able to use the DMA controller to offload the CPU and play smooth music without loading the CPU, but we ran out of time.
If you’re v. smart, you might be able to get stereo going!
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