TFT - Arduino Sketches: Tools and Techniques for Programming Wizardry - page 226

■ isValid()

■ image()

The hardware needed to use the example in this chapter includes:

Arduino Uno

■

LM35 Temperature sensor

■

Adafruit ST7735 TFT breakout board (available at http://www.adafruit
.com/product/358 )

■

Micro-SD card

■

Breadboard

■

Connection cables

■

10-kilohm resistor

■

Light Dependent Resistor

■

You can i nd the code download for this chapter at http://www.wiley
.com/go/arduinosketches on the Download Code tab. The code is in the
Chapter 13 download folder and the i lename is chapter13.ino .

Introduction

Computer enthusiasts love their hardware, and one of the most loved (and most
feared) devices is the humble monitor. When you talk about a monitor, some
people immediately think about a previous technology, known as CRT.
Cathode Ray Tubes (CRT for short) was the technology used by televisions
and monitors for decades. Put simply, it is an electron canon; a device at one end
blasts out electrons onto a l uorescent screen. Large magnets divert the electron
beam to hit specii c places on the screen, causing the screen to light up at distinct
points. Of course, electrons are highly susceptible to atmospheric impurities,
and even air, so the gun and the screen were encased inside a large glass shell
in a vacuum. To avoid becoming too fragile, the glass was often thick, and to
block most X-ray radiation, the glass used often was lead glass. Devices could
be made fairly small but were often deep. (In extreme cases, CRTs were as deep
as they were wide, but most were about one-half as deep as they were wide.)
They have been used as televisions, of course, but also on oscilloscopes, data
output, signaling, aircraft cockpits, and even as memory devices.
CRT screens could produce beautiful images but at a cost. The bigger they
were, the heavier they got. A 27-inch CRT TV could weigh more than 100 lbs
(40 kg). One of the largest and heaviest was a 40-inch screen that weighed in