28128 Parallax Inc, 28128 Datasheet - Page 23

• Manufacturer Part Number: 28128
• Description: KIT BASIC ANALOG/DIGI PARTS ONLY
• Manufacturer: Parallax Inc

Specifications of 28128

• Accessory Type: ADC, DAC
• Product: Microcontroller Accessories
• For Use With/related Products: BASIC Stamp® 2 and Board of Education
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

The Output
As you adjust the potentiometer, note how the LED at the voltage follower's analog
output can vary in brightness. Meanwhile the LED circuit driven by P12 either turns on
or off. This characterizes the difference between analog voltage and digital (binary)
voltage.
The output displayed in the Debug Terminal should resemble the output shown in Figure
1-9. The state of P7 will either be 0 or 1. Correspondingly, the LED circuit driven by P12
will either be off or on.
Adjust the potentiometer until you have found the threshold voltage. You will know
when you've found it because the Debug Terminal will indicate that the state of P7 skips
back and forth between 0 and 1 with just the slightest adjustment of the pot. Note the
position of the potentiometer. After we build a DC voltmeter in Chapter #3, we can find
out how close we are to 1.4 volts, which is the actual threshold voltage of a BASIC
Stamp I/O pin when it's functioning as an input.
Figure 1-9
Debug Terminal
Output for Program