Circuit Extern DE2

You can connect a 7 segment display to the GPIOs. But you should limit the current by adding a resistor in series with every LED diode of the 7 segment display. The value of the resistor depends on the amount of current Iled that you want to use for the LED. The voltage drop over your LED will be ~1.45 Volt, the logic signal from the FPGA 3.3 Volt.

There is already a 47 Ohm series resitor for every output to protect the FPGA for first order "accidents".

Using Ohm's law you can calculate the resistance that you require.

R = ((3.3 Volt - 1.45 Volt) / Iled) - 47 Ohm

e.g. for a LED current Iled = 5 mA this boils down to:

R = ((3.3 - 1.45) / 0.005) - 47 = 323 Ohm

In this case you could use series resistors of 330 Ohm.

It depends of course on the LEDs in the 7-segment displays how much current that should be used.

There is also a limitation on the maximimum current sourcing from your FPGA pins (8 to 24 mA) depending of the I/O standard you use, as well as the combined current sourcing from consecutive pins in I/O banks.

So you could use resistors of 150 Ohm.