20140313 (Th) ASETNIOP Keyboard

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

Enough background.
Parts were ordered from Digikey.  Shipping for Digikey was $5.10.  I live in St. Paul, Minnesota.
  2 @ TRRS M-M cables were ordered from a North American seller on eBay.

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.

To do:
• Finish pseudo code
• Write code
• Sketch µprocessor schematic.  Neopixel and 2 comm ports
• Design stripboard for handles