fixed cdc.py bug

[hstarmans]

fixes #101.
You can test the issue by making the following on a fpga. This basically makes sdo equal to sdi.

from amaranth import Elaboratable, Module
from luna.gateware.interface.spi import SPIDeviceInterface
from luna.gateware.utils.cdc import synchronize

from hexastorm.platforms import Firestarter


class DebugSPIExample(Elaboratable):
    """Hardware meant to demonstrate use of
    the Debug Controller's SPI interface copied from Luna"""

    def __init__(self):
        # Base ourselves around an SPI command interface.
        self.interface = SPIDeviceInterface(clock_phase=1)

    def elaborate(self, platform):
        m = Module()
        board_spi = platform.request("debug_spi")

        # Use command interface.
        m.submodules.interface = self.interface

        # Synchronize and connect SPI.
        spi = synchronize(m, board_spi)
        m.d.comb += self.interface.spi.connect(spi)

        # Turn on a single LED, to show something's running.
        led = platform.request("led", 0)
        m.d.comb += led.eq(1)

        # Echo back the last received data.
        m.d.comb += self.interface.word_out.eq(self.interface.word_in)

        return m

You then write bytes and see if you get them back. This is not the case with amaranth at the moment.

import spidev
from gpiozero import LED

spi = spidev.SpiDev()
spi.open(0, 0)
spi.mode = 1
chip_select = LED(select_pin)
chip_select.on()
spi.max_speed_hz = round(1e6)
bts = [210, 222, 230]
previous_byte = None
for idx, byte in enumerate(bts):
    chip_select.off()
    byte_received = spi.xfer([byte])[0]
    chip_select.on()
    if idx != 0:
        try:
            assert previous_byte == byte_received
        except AssertionError:
            print(previous_byte)
            print(byte_received)
            raise Exception("Test failed: not equal")
    previous_byte = byte

[antoinevg]

Thank you for submitting this PR!

The changes you made does resolve the compilation problem for your case but unfortunately it also does away with the recursive operation on elements of type Pin.

I'm going to close this PR in favour of an alternative PR that fixes the underlying problem: #263

[hstarmans]

@antoinevg thanks for your feedback and fix... I will try that one..