Complete FPGA Projects

34.1 LED blinker (the FPGA "Hello World")

Constraints (e.g., Basys 3):

Open-source flow for a Lattice iCE40 board:

library ieee;
use ieee.std_logic_1164.all;

entity blinky is
  generic (CLK_FREQ : positive := 100_000_000);
  port (
    clk : in  std_logic;
    led : out std_logic);
end entity;

architecture rtl of blinky is
  signal cnt   : integer range 0 to CLK_FREQ / 2 - 1 := 0;
  signal state : std_logic := '0';
begin
  process (clk)
  begin
    if rising_edge(clk) then
      if cnt = CLK_FREQ / 2 - 1 then
        cnt   <= 0;
        state <= not state;          -- toggle every 0.5 s → 1 Hz blink
      else
        cnt <= cnt + 1;
      end if;
    end if;
  end process;
  led <= state;
end architecture;

set_property -dict { PACKAGE_PIN W5  IOSTANDARD LVCMOS33 } [get_ports clk]
set_property -dict { PACKAGE_PIN U16 IOSTANDARD LVCMOS33 } [get_ports led]
create_clock -period 10.000 -name sys_clk [get_ports clk]

yosys -m ghdl -p 'ghdl --std=08 blinky.vhd -e blinky; synth_ice40 -json blinky.json'
nextpnr-ice40 --up5k --package sg48 --json blinky.json --pcf board.pcf --asc blinky.asc
icepack blinky.asc blinky.bin && iceprog blinky.bin

34.2 Multiplexed 4-digit seven-segment counter

Combine: a 1 kHz refresh tick, a 2-bit digit selector, a BCD counter incremented at 1 Hz, the seven-segment decoder (§12.6), and active-low anode drivers. Teaches clock enables, hierarchy, and time-multiplexing.

34.3 Stopwatch / digital clock

Buttons (debounced, edge-detected) for start/stop/reset/lap; cascaded BCD counters for minutes:seconds:hundredths; FSM for modes.

34.4 UART echo & command processor

UART RX → FIFO → command parser FSM → register writes / LED control → UART TX responses. Test from a PC terminal (PuTTY, screen, Python pyserial).

34.5 VGA pattern generator & Pong

VGA timing generator (§28.4), color bars, moving sprites, collision detection, score display with a character ROM — a classic complete project combining counters, FSMs, ROMs, and arithmetic.

34.6 PWM, audio & sensors

PWM LED dimming and servo control, sigma-delta DAC for audio tones, SPI ADC readout, I2C temperature sensor display.