Data Sheet

Arty FPGA Board Reference Manual

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general purpose push button. Note that it is also tied to the RST pin on J7 of the shield connector and to the

FT2232 UART device via JP2, though these connections are not shown in the figure below.

Figure 9.1. Arty GPIO.

The four individual high-efficiency LEDs are anode-connected to the FPGA via 330-ohm resistors, so they will turn

on when a logic high voltage is applied to their respective I/O pin. Additional LEDs that are not user-accessible

indicate power-on, FPGA programming status, and USB and Ethernet port status.

9.1 Tri-color LEDs

The Arty board contains four 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 FPGA 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.

Note: 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.