The last time I bought a notebook I grabbed a yellow notebook because I hadn't used a yellow notebook in awhile. I bought wide rule by accident. First world problems.
I show a Digikey shopping cart below but there are a couple things on there I didn't list like stripboards which are cheaper to buy from eBay and the µprocessor. I don't list the µprocessor because I don't know if I'll go with the Trinket or DigiSpark. I also ordered two TRRS male to male cables from eBay because they were inexpensive.
TRRS cable. Notice there are four conductors
Parts were ordered from Digikey. Shipping for Digikey was $5.10. I live in St. Paul, Minnesota.
It was decided to use 3.5mm TRRS (Tip-Ring-Ring-Shield) plugs on both the USB module, where the controller will reside and the handles.
The plugs and cords will provide a modular design and allow for easy upgrades to the handles.
An Arduino library was found for the MCP23008-E/P.
Schematics for the handle hadware was sketched and drafted. Each handle has a different colored thumb switch cap to diffeentiate. They will have a diffent address. The address is set by tying the A0, A1 and S2 pins high or low (on the MCP23008-E/P chips). This could be done with switches and pull-up resistors (or pull-down resistors) but they will be soldered. The ciruit will be built on stripboard which is already in my stock.
The Digispark was researched to see if it would make a suitable candidtae. It has been shown to work with I2C devies, mostly LCD screens. The I/O expanders are I2C devices.
Digispark SDA - Pin 5, PB0, MOSI
Digispark SCL - Pin 7, PB2, ADC1
More work was done on the pseudo code. The thumb switches were included as well as the numberLock and capsLock.
• Finish pseudo code
• Write code
• Sketch µprocessor schematic. Neopixel and 2 comm ports
• Design stripboard for handles