As I was working on the power supply, I began to think about what I wanted from the "control system".

My initial plan was to stick the power supply board, my current fm transmitter, and bluetooth receiver into a box, with some control buttons leading out of it. This would have worked well enough, is easy to design, and is cheap. However, this isn't exactly the best solution for a number of reasons. I would have to sacrifice and waste unnecessary space with my "stock" parts, which also carry some issues. The fm transmitter has this "idle" feature, where it turns off if there is no audio being played. There are some situations where I need navigation audio played over the stereo, but with no background music. The fm transmitter controller will also need to be set out somewhere to control the transmission frequency, using up more space. The bluetooth receiver does what it needs to well, but has slight audio interference issues.

I could 'simplify' the system by integrating both the bluetooth audio receiver and fm transmitter into the control system. This would leave the power supply portion to be only that, a power supply. This also means I would need to find the parts used in the fm transmitter and bluetooth receiver, and incorporate them into the control system. The bluetooth receiver uses your standard OVC3860, and there are nice and cheap little breakouts for them on ebay. The FM transmitter was a pain to identify (vague, unmarked ics), but eventually I found that it uses the QN8027, a nice I2C controlled fm transmitter deal. The only "nice" place I can find it for sale is on aliexpress, and that's still a bit of a jump from what I'm used to.

I plan on having this all connect to an LPC11U35FHI33 ARM microcontroller, which controls this LCD. This is a large (and a little more expensive) jump from my initial plans, but it's nothing I'm not already used to. I also want to get into selling things on Tindie, so this could be a good start.

The following picture should hopefully describe what I want to accomplish:

TLDR: Feature creep