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3.6.1
User Push-buttons, Switches and LEDs on FPGA
The board provides four push-button switches connected to FPGA as shown in
Figure 3-12
Connections between the push-button and Cyclone V SoC FPGA
. Each of these switches is debounced
using a Schmitt Trigger circuit, as indicated in
Figure 3-13
. The four outputs called KEY0, KEY1,
KEY2, and KEY3 of the Schmitt Trigger devices are connected directly to the Cyclone V SoC
FPGA. Each push-button switch provides a high logic level when it is not pressed, and provides a
low logic level when depressed. Since the push-button switches are debounced, they are appropriate
for using as clock or reset inputs in a circuit.
Figure 3-12 Connections between the push-button and Cyclone V SoC FPGA
Pushbutton released
Pushbutton depressed
Before
Debouncing
Schmitt Trigger
Debounced
Figure 3-13 Switch debouncing
