Monday, May 25, 2015

RPi GPIO Test #4: Signal Inversion

In the previous example, a pushbutton was "soft wired" to an LED in such a way that the LED was ON when the pushbutton was up, and OFF when the pushbutton was down. This is the reverse of what you would usually expect, so in the present system configuration (GPIO_TEST4.sys), the signal is inverted using an instance of the FB_NOT function block type so that the LED is ON when the pushbutton is down.

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