I’m working on a project which requires the use of a HAT to collect audio into a Raspberry Pi 3. The HAT that we have been using is no longer available to buy and therefore I would like to design and build my own. However, I’m a complete noob when it comes to designing and interfacing with this type of hardware.
Does anybody have experience in this that could point me in the direction of how to get started, particularly on writing the drivers to connect to Pi?
My idea is to create the simplest device possible - It should have 3 connections for the Microphone (Bias, Signal and Ground), a low power Audio ADC or CODEC and a connection to the PI. The Pi should then see this as a sound card and be able to pass the data to an ALSA Audio stream.
I’ve had a look at USB devices but there are two problems with them. The first is that anything USB powered is quite power hungry for the raspberry pi which is a problem for battery powered applications. The second problem is that the low-cost ones like the Behringer UC A202 are a little unstable (not so much that you would notice on an audio recording but for measurement science it’s a noticeable uncertainty).