28129 Parallax Inc, 28129 Datasheet - Page 31

• Manufacturer Part Number: 28129
• Description: TEXT BASIC ANALOG & DIGITAL
• Manufacturer: Parallax Inc
• Type: Programmingr

Specifications of 28129

• Style: Book
• Title: Basic Analog and Digital
• Contents: Basic Analog and Digital Text
• Product: Microcontroller Accessories
• Lead Free Status / RoHS Status: Not applicable / Not applicable

Before making a PBASIC program telling the BASIC Stamp how to interface with this
circuit, it's essential to understand how the circuit works. The LEDs are pretty
straightforward. Set P4 high and the LED lights up; set P4 low and the LED goes dark
again. The LED circuit connected to P5 works the same way.
Now, what about the pushbuttons? Let's look at what pin P0 sees when the pushbutton is
pressed, then not pressed. When the pushbutton is pressed, P0 gets connected directly to
Vdd, which is 5 volts. P0 sees a high signal. When the pushbutton is not pressed, P0 is
connected to Vss (0 volts) through the 10 k
concept applies to both pushbuttons shown in Figure 2-2.
Figure 2-3 shows a breadboard example of the circuit schematic. Of the two BASIC
Stamp I/O pins used for the pushbuttons, the lower pin (P0) is connected to the right
pushbutton. Likewise, the right pin (P1) is connected to the lower pushbutton. The reason
P1
P0
P5
P4
220
Vss
Ω
Vdd
470
LED
Vss
10 k
Ω
220
Ω
Vss
Ω
Vdd
470
LED
Vss
10 k
Ω
resistor. Then P0 sees a low signal. This
Ω
Figure 2-2
Schematic featuring two
pushbutton circuits and
two LED circuits.