The Really Brief Guide on:
The Spyglass User Interface Board

Written by Pascal Stang | Updated: Sunday February 20, 2011

Spyglass UI Board Front	Spyglass UI Board Back

Spyglass UI Features:

All functions controlled over I2C bus
Just 2 signal wires + 2 wires for power and ground!
LCD display: 4 line x 20 character (HD44780 standard type)
- Yellow-green LED backlight

7 user pushbuttons
2 user-controlled LEDs plus power LED
Piezo beeper for alerts and user-interface feedback
Operates from single 5V power supply
Can be controlled by any I2C-capable microcontroller or system
- AVR, ARM, PIC processors and more
- Basic Stamps
- PC-based I2C communication adapters
Example AVR code and function library included in AVRlib
Board size: 4" x 4" x 1" (LxWxH)

Spyglass UI Pinout:

The pinout is shown looking into the connector on the back.

How to operate the Spyglass UI:

The Spyglass UI Board is controlled via three (3) PCF8574 I2C 8-bit I/O expanders, and one 8-bit I2C DAC. The parts are as used as follows:

Part	I2C Address	Function
PCF8574 #1	0x40	Reading the pushbuttons
PCF8574 #2	0x42	Controlling the LCD data lines DB0-7
PCF8574 #3	0x44	Controlling the LCD control signals RS, R/W, E, and the LEDs and piezo beeper
MAX518 DAC	0x58	Controlling LCD Contrast

Each PCF8574 has 8 I/O pins which can be read and written via the I2C bus. Here is how they are connected.

Datasheets for select parts:

Example source code:

Written by Pascal Stang | Updated: Sunday February 20, 2011