It must be a sign

It was a dark and wet day at Guildford train station. Platform 5 is one of the few places in the world to be more than 10 metres from a Costabucks. On the one hand I could run up & down the stairs, join the queue, decide exactly which type of (basically all the same) beverage I wanted before returning with my prize, or I could just sit there and make do with a faint aroma wafting across from Platform 1. If the train were to arrive and depart whilst I am on this quest then it won't be just the milk that will be frothing.

To aid my naturally poor decision making ability, I glance up at an information display to see how much time I have to play with. I notice the sign full of LEDs displaying the next train and the stations it will stop at.

I start to count how many dots in the characters and wonder how they are multiplexed. I think about how much processing is done behind the twinkly lights and if it uses as much energy in one hour as a kettle boiling one cup of water to make instant coffee at home. I decide that Costabucks will probably survive without my patronage and before I know it, the train arrives.

Later that day I actually get round to practising a song (for one band or the other!) and I look at my dark fretboard and think wouldn't it be great if it had lots of LEDs on it. I've never seen a bass guitar with an LED sign on the fretboard. There really isn't enough room for it and it's a silly idea. Unfortunately I'm the sort of person that believes these are exactly the right reasons for building one anyway.

I have a reel of 800 RGB LEDs sitting in the cupboard (Everlight SAGBB7C). These use the standard 5050 SMD package with 6 pins. Each led will require its own driver channel and for any decent sized display that's a lot of complex-stuff-to-go-wrong to be installing inside a bass neck. 

The WS2812B LEDs used on my 'damp' project would be ideal. The same 5mm square SMD package, but this time only 4 pins. Power, ground, data in and data out. They use a clock-less serial data stream based on high and low mark space ratios giving 1's and 0's. The main bonus here is that apart from the LEDs themselves, there doesn't need to be much else in the neck - ie less-to-go-wrong-where-I-can't-fix-it. The downside is that these are NOT sitting in a cupboard, so it's more on the shopping list.

I want this bass to look reasonably normal when its off, so I'm going to purchase a jazz bass style body and neck online and pop a few RGB LEDs in along with the control circuitry. With multi-coloured action going on, this Jazz Bass has ended up with the name Jelly Bean before it has even begun. 

With confirmation of my mental age out of the way, it's time to work out how it is all going to hang together. Some prototyping is going to be needed up front before I spend serious money on the body as I need to prove that a (simple to solder) Microchip PIC will be able to control separate daisy chains of LEDs in parallel. There are many other devices out there which may be more suitable but I already have a PICkit3 programmer, so it's PIC or bust.