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Intro to Physical Computing Syllabus code, circuits, & construction
Programming the PIC using PicBasic Pro Serial in and out (using serin2 and serout2) |
Using a powered oscillator with the PIC |
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| Breadboards are convenient for prototyping, but they're not the most efficient conductors. They have a characteristic impedance, or resistance to change in voltage (think of it kind of like voltage inertia). In particular, they can affect the oscillation of a microcontroller's clock when it's very fast. When yo're using a fast crystal, for example 20MHz, you may find that your microcontroller doesn't run. One way around this is to use a powered oscillator.
A powered oscillator may give you a stronger and more regular clock signal than a crystal for your microcontroller, though they take power and space on your board. This example uses a TTL-level crystal clock oscillator. If you want to use an oscillator with the PIC instead of a crystal, wire it as follows:
Note that some documentation may number the pins as Pin 1, 7, 8, and 14. This is because the oscillator fits a standard 14-pin socket. As with most DIP integrated circuits, pins are numbered in a U-shape. Below is a picture of a 18F452 PIC wired with an oscillator.
When you use a powered oscillator, you should also make a point of decoupling your power regulator properly, as follows:
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