Arduino uno User Manual

• SCALE_WIDTH and SCALE_HEIGHT define the width and height of the thermome-
ter’s scale.
• The variable current_temperature holds the last temperature we measured.
last_measurement contains the time stamp in milliseconds when we last
measured the current temperature. We need this because we don’t want
to measure the temperature permanently, but only every few seconds.
• TV is an instance of the TVout class, and we’ll use it for accessing the TV
screen using the Arduino.
Next we define the setup function:
Video/TvThermometer/TvThermometer.ino
void setup() {
TV.begin(PAL, SCREEN_WIDTH, SCREEN_HEIGHT);
TV.bitmap(0, 1, thermometer);
TV.select_font(font4x6);
TV.set_cursor(20, 4);
TV.print("40");
TV.set_cursor(20, 24);
TV.print("30");
TV.set_cursor(20, 44);
TV.print("20");
TV.set_cursor(20, 64);
TV.print("10");
}
We call the begin method of the TV object. We set the analog TV standard to
PAL, and we set the screen’s width and height. If your TV set prefers NTSC,
you have to replace the first argument with NTSC . After that, we invoke the
bitmap method to draw the thermometer image to the screen. Its X position is
0, and its Y position is 1.
The thermometer’s image doesn’t contain numbers next to its scale, so we
add the numbers in our program. Therefore, we have to select the font we’re
going to use by using the select_font method. TVout’s font capabilities are quite
impressive. It comes with three fixed-width fonts (4x6, 6x8, and 8x8 pixels)
that are sufficient for most purposes. It also supports variable-width fonts,
and it even allows you to define your own. Here we use a font that’s 4 pixels
wide and 6 pixels high. The set_cursor method moves the cursor to a certain
screen position, and print prints text to the current cursor position.
The loop function implements the rest of our thermometer’s business logic.
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Building a TV Thermometer • 137
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Arduino uno Specifications

General

Form factor	Arduino
Certification	RoHS, FC, CE
Processor model	-
Processor frequency	- MHz
Microcontroller model	ATmega328
Microcontroller frequency	16 MHz
DC input voltage	7-12 V
Operating voltage	5 V
DC current per I/O pin	40 mA
Flash memory	0.032 MB
Maximum internal memory	- GB
SRAM (Static Random Access Memory)	2 KB
EEPROM (Electrically Erasable Programmable Read-Only Memory)	1 KB
Wi-Fi	No
Number of analog I/O pins	6
Number of digital I/O pins	14

Weight and Dimensions

Board dimensions	53.4 x 68.6 mm