This system configuration utilizes the LED/Pushbutton Testbed for the Raspberry Pi.

Upon launching the system configuration, the test window shown above is opened.

• Clicking on the RUN radio button triggers the START input of the RUN FB in the GPIO.CLOCK Resource, following which the following sequence of operations occurs every 50 milliseconds:
  • An event is passed from the RUN.EO output to the CLK.REQ input in the GPIO.CLOCK Resource.
  • This event is then passed to the CLK FB in the GPIO.IO Resource via the Local Multicast CLK channel.
  • The event is then passed from the CLK.IND output to the BUTTON.REQ input in the GPIO.IO Resource.
  • The button state is read to BUTTON.X (TRUE=up, FALSE=down) and is passed to LED.X.
  • An event is passed from BUTTON.CNF to LED.REQ.
  • The value at LED.X is written to the LED output (TRUE=high=ON, FALSE=low=OFF)
• The above cycle of operations produces the observable effect that the LED is OFF when the pushbutton is pressed, and ON when the pushbutton is released.
• Clicking the STOP radio button stops the operation of the RUN FB, with the result that pressing and releasing the pushbutton has no further effect on the LED state until the RUN radio button is clicked again.