28123 Parallax Inc, 28123 Datasheet - Page 80

• Manufacturer Part Number: 28123
• Description: TEXT WHAT'S A MICROCONTROLLER
• Manufacturer: Parallax Inc
• Type: Programmingr

Specifications of 28123

• Style: Book
• Title: What's a Microcontroller?
• Contents: Whats a Microcontroller? Text
• Product: Microcontroller Accessories
• Core Processor: PIC16C57c
• Flash: 128 Bytes
• Operating Supply Voltage: 9 V
• Board Size: 31 mm x 16 mm
• Lead Free Status / RoHS Status: Not applicable / Not applicable

Chapter #3: Digital Input - Pushbuttons
FOUND ON CALCULATORS, HAND HELD GAMES, AND APPLIANCES
How many devices with pushbuttons do you use on a daily basis? Here are a few
examples that might appear in your list: computer, mouse, calculator, microwave oven,
handheld remote, handheld games, and VCR. In each device, there is a microcontroller
scanning the pushbuttons and waiting for the circuit to change. When the circuit changes,
the microcontroller detects the change and takes action. By the end of this chapter, you
will have experience with designing pushbutton circuits and programming the BASIC
Stamp to monitor them and take action when changes occur.
RECEIVING VS. SENDING HIGH AND LOW SIGNALS
In Chapter #2, you programmed the BASIC Stamp to send high and low signals, and you
used LED circuits to display these signals. Sending high and low signals means you used
a BASIC Stamp I/O pin as an output. In this chapter, you will use a BASIC Stamp I/O
pin as an input. As an input, an I/O pin listens for high/low signals instead of sending
them. You will send these signals to the BASIC Stamp using a pushbutton circuit, and
you will program the BASIC Stamp to recognize whether the pushbutton is pressed or not
pressed.
ACTIVITY #1: TESTING A PUSHBUTTON WITH AN LED CIRCUIT
If you can use a pushbutton to send a high or low signal to the BASIC Stamp, can you
also control an LED with a pushbutton? The answer is yes, and you will use it to test a
pushbutton in this activity.
Introducing the Pushbutton
Figure 3-1 shows the schematic symbol and the part drawing of a normally open
pushbutton. Two of the pushbutton’s pins are connected to each terminal. This means
that connecting a wire or part lead to pin 1 of the pushbutton is the same as connecting it
to pin 4. The same rule applies with pins 2 and 3. The reason the pushbutton doesn’t just
Other terms that mean send, high/low, and receive:
described in different ways. You may see sending referred to as transmitting, controlling, or
switching. Instead of high/low, you might see it referred to as binary, TTL, CMOS, or
Boolean signals. Another term for receiving is sensing.
Sending high/low signals is