When [Sami Pietikäinen] realized that the Bluetooth built into his car didn’t support audio, he didn’t junk it and buy a Tesla. Instead, he decided to remedy the problem by building a small Bluetooth device that plugged into the Aux socket. To do this, he used a Raspberry Pi Zero with a pHAT DAC (Digital to Audio Converter). That’s perhaps using a sledgehammer to crack a walnut, but sometimes you work with what you have. The interesting part is to be found in what he did next: he used Yocto to optimize the device down to make it as simple and straightforward as possible.
That’s because the Raspbian OS he used for the first version does way more than was needed: The device just has to handle Bluetooth and the audio output, and really didn’t need all of the other stuff that Raspbian tries to install and run.
So for the second version, he dispensed with Raspbian and used Yocto, a project that allows you to create a customized Linux distribution. By stripping out the stuff the project does not need, he made the project much faster and more streamlined. He used Meta-raspberrypi, a Board Support Package (BSP) that provides the basis for running Yocto on a Pi, then tweaked a pre-built Yocto image to disable all of the features that he did not need.
The result is a device that is much simpler and which boots up and is ready to play music in about five seconds. That’s a considerable improvement over the thirty to sixty-second boot time of the standard Raspbian image (assuming it boots at all), and is a nice example of how simpler is sometimes better.