Arty Z7 Reference Manual
Transfer Multisort Elektronik / tme.eu
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Additional LEDs that are not user-accessible indicate power-on, PL programming status, and
USB and Ethernet port status.
12.1 Tri-Color LEDs
The Arty Z7 board contains two tri-color LEDs. Each 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 signal corresponding to one of these colors high 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 signals 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.
Digilent strongly recommends the use of pulse-width modulation (PWM) when driving the
tri-color LEDs. Driving any of the inputs to a steady logic ‘1’ will result in the LED being
illuminated at an uncomfortably bright level. You can avoid this 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 50% and 0% causes the different colors to be illuminated at different
intensities, allowing virtually any color to be displayed.
13 Mono Audio Output
The on-board audio jack (J13) is driven by a Sallen-Key Butterworth Low-pass 4th Order
Filter that provides mono audio output. The circuit of the low-pass filter is shown in Figure
14.1. The input of the filter (AUD_PWM) is connected to the Zynq PL pin R18. A digital
input will typically be a pulse-width modulated (PWM) or pulse density modulated (PDM)
open-drain signal produced by the FPGA. The signal needs to be driven low for logic ‘0’ and
left in high-impedance for logic ‘1’. An on-board pull-up resistor to a clean analog 3.3V rail
will establish the proper voltage for logic ‘1’. The low-pass filter on the input will act as a
reconstruction filter to convert the pulse-width modulated digital signal into an analog voltage
on the audio jack output.
