如何在FPGA板上使用VHDL显示句子

Question

I am just wondering if it is possible to display a sentence, for example "SOLD OUT", on the 7-segment display of the FPGA board where I can only show four letters.

I want it to display SOLD then OUT.

If it is possible to implement that, how can I do it? Clock divider?

Answer 1

You start by researching what the board does. How does it connect to the LCD display? What are the waveforms required to drive a value to the display. It will be different for different boards. The Digilent boards tend to be common Anode. Some Altera boards connect all four 7-segment displays directly to FPGA IO (wastes IO, but who cares when you have plenty).

Next you determine, how do I display a character on the display. What holds the value? What translates the value from an internal representation, such as ASCII to the value on the display.

WRT clocks, my preference is to use a common FPGA clock and use load enables that provide periodic indication it is time to load the other image.

Think about how fast you should be switching the display? My recommendation is to make sure you display each value for 1 sec before switching and adjust after you see it working. If you decrease the display time too much, your display will blur because neither value is displayed long enough.

Next how do I display 4 characters?

Next how do I make the characters shift or alternate between different values. This could be a character wide shift register, it could be two different display registers.

In each of these steps you should be drawing a picture of the hardware before writing any code.