button_clock.py

from amaranth import *
from amaranth_boards.ulx3s import ULX3S_85F_Platform

class Counter(Elaboratable):
    def elaborate(self, platform):
        m = Module()

        counter = Signal(8)
        leds = [platform.request("led", n) for n in range(8)]

        # Increment counter every clock cycle in the default "sync" domain
        m.d.sync += counter.eq(counter + 1)

        # Output to individual LEDs
        m.d.comb += [led.o.eq(bit) for led, bit in zip(leds, counter)]

        return m

class Top(Elaboratable):
    def elaborate(self, platform):
        m = Module()

        button_up = platform.request("button_up")

        # Read clock from button
        m.domains.button_clock = ClockDomain("button_clock")
        m.d.comb += ClockSignal("button_clock").eq(button_up.i)

        m.submodules.counter = DomainRenamer("button_clock")(Counter())

        return m

platform = ULX3S_85F_Platform()
platform.build(Top(), do_program=True)