FPGA: FPGA Seven Segment LEDs
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FPGA Seven Segment LEDs The use of seven segment LED's on an FPGA is a tricky business. The things one must concern one's self with include:
  • Converting some 4 bit number to the 7 segment wires (and, if desired, the decimal point)
  • Mapping the 7 segment wires to the corect pins of the FPGA that mate to the seven segment board
  • Mapping the inputs tot he seven segment board to the actual seven segment display lights
The mapping algorithm is a two step process for all boards, but is most clear with Tony Burch's seven segment board. Note: I really like the BurchEd product line . My father, Ed, and our friend LaFarr purchased some of Tony's equipment and are really happy with it. You can read more about our purchase decision here. I've written some Perl and Verilog code to help with this process. What I wanted was a design such that given an input of a 4 bit binary number (a vector), the [named] connector to FPGA to which the seven segment display is connected, and the specific LED that I wanted to drive, I could generate the necessary components to drive the seven segment LED. Put another way:
	4 bit vector -> 7 bit vector -> 7 individual wires -> .ucf file -> LEDs
Keep in mind that I have a particular reasoning for the 4 bit vector to 7 bit vector conversion before the 7 indiviaul wires. What I'm trying to accomplish is that with the simulator 7 individual wires take 7 lines of the wave output window. Instead, as a 7 bit vector, there is only one line item in the wave output window. Then, I convert it to individual wires and then pump it out to the LEDs.