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STAMP 2 Communications And Control Projects.pdf

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INTERFACES FOR THE MICROPROCESSOR 21<br />

+5V<br />

<strong>STAMP</strong> 2<br />

S1<br />

N/C<br />

BS 2<br />

P0<br />

10K<br />

Figure 2-4 Active low input—normally<br />

closed input.<br />

+5V<br />

<strong>STAMP</strong> 2<br />

1K<br />

+5V<br />

BS 2<br />

P0<br />

LED<br />

21<br />

23<br />

LED is "sunk" to ground.<br />

Figure 2-5<br />

<strong>STAMP</strong> 2 output<br />

“sunk” to ground.<br />

Interfaces for the Microprocessor<br />

Sometimes it’s necessary to interface a microprocessor to other ICs or microprocessors.<br />

The circuit in Fig. 2-9 depicts a bipolar transistor turned on by the <strong>STAMP</strong> 2 on pin P0.<br />

Transistors are ideal interfacing devices; they require a small current to turn on and can<br />

easily isolate the next circuit stage. This circuit can be thought of as an inverting buffer,<br />

since the signal output from the <strong>STAMP</strong> 2 is a positive pulse. The output after the transistor<br />

becomes a “low,” thus creating an inverted and buffered signal. Many circuits require

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