Digilent Genesys ZU Reference Manual page 34

Genesys ZU also has two push‐buttons and one green LED connected to the Zynq PS: push‐buttons BTN0
and BTN1 are connected to MIO11 and MIO10, respectively, and the green LED is connected to MIO21.
9.1. Push‐Buttons
The push‐buttons are "momentary" switches that normally generate a low output when they are at rest,
and a high output only when they are pressed.
9.2. Slide Switches
The slide switches generate constant high or low inputs depending on their position: when the slide is in
a low position (i.e. close to the lower board edge), the generated input is low; when the slide is in a high
position (i.e. close to the center of the board), the generated input is high.
9.3. Tri‐Color LED
The tri‐color LED has three input signals that drive the cathodes of three smaller internal LEDs: one red,
one blue, and one green. Driving the input signal corresponding to one of these colors low will illuminate
the internal LED. The input signals are driven by the Zynq PL through a transistor, which inverts the
signals. Therefore, to light up the tri‐color LED, the corresponding PL pins need to be driven high. The tri‐
color LED will emit a color dependent on the combination of internal LEDs that are currently being
illuminated. For example, if the red and blue signals are driven high and green is driven low, the tri‐color
LED will emit a purple color.
Note: Digilent strongly recommends the use of pulse‐width modulation (PWM) when driving the tri‐colo
LEDs. Driving any of the signals to a steady logic '1' will result in the LED being illuminated at an
uncomfortably bright level. This can be avoided by ensuring that none of the tri‐color signals are driven
with more than a 50% duty cycle. Using PWM also greatly expands the potential color palette of the tri‐
color LED. Individually adjusting the duty cycle of each color between 0% and 50% causes the different
colors to be illuminated at different intensities, allowing virtually any color to be displayed.
9.4. Green LEDs
The individual high‐efficiency LEDs are anode‐connected to the Zynq Ultrascale+ via 330‐ohm resistors,
so they will turn on when a logic high voltage is applied to their corresponding I/O pin.