Summary

A breadboard-friendly breakout board with several common and normally bothersome devices and interfaces already taken care of.

Reasoning

The product would deal with two annoyances in breadboarding certain interfaces, each depending on the interface. Some interfaces have only a surface-mount package available; the breakout provides for presenting a breadboardable interface. Some interfaces simply involve a fleet of several components always in the same configuration; the utility board permanently fixes some of these components together, presenting a lower number of pins to the breadboard resulting in less manual wiring (after the initial investment of construction).

Specification

• Power input, probably with common ground connection and conditioning capacitors
• 20MHz crystal with capacitors
• PIC-style /MCLR RC network
  • Isolated from /MCLR pin by a Schottky diode (see ICSP)
• 5-pin ICSP header with jumper wires to breadboard for Vpp, PGC, PGD
  • Vpp header pin shared with /MCLR but not isolated
• USB mini-B or micro-B with pins or jumper wires to breadboard for D+ and D-
  • Jumper, DIP switch, or auto-select mechanism to use USB as supply voltage
• The following, which might be better deferred to a separate board
  • Some (maybe 2 to 8) 1-line input buttons with pull-up resistors
  • Some (maybe one per button) 1-line LED outputs with current-limiting resistors
    • The LEDs should have at least somewhat distinguishing colors for monitoring from across the room

Progress

• Tasks
  • Schematic has been created in gschem.
• Materials
  • USB mini-B SMD connector
  • 20MHz SMD crystal with either through-hole or SMD capacitors
  • Breakaway headers
  • 10K pull-up resistors, either through-hole or SMD
  • Through-hole LED/resistor pairs in three colors

Requisites

• Tasks
  • PCB layout (gEDA PCB)
  • PCB fabrication (probably OSHPark)
  • PCB assembly
  • PCB testing
• Optional
  • Determine values for the current-limiting resistors for the LEDs. 150 ohms should probably be adequate for both 5V and 3.3V, but this may vary both by the Vf of the LED and the efficiency of the LED model.
• Materials
  • Optional
    • SMD LED/resistor pairs would reduce the amount of drilling required. See notes for resistor values.