main.py

from amaranth import *
from amaranth.hdl import IOPort
from amaranth.build import *
from amaranth.vendor import GowinPlatform
from amaranth_boards.resources import *

# Issue without iter_port_constraints_bits patch
#
# Traceback (most recent call last):
#   File "/Users/jeanthomas/Documents/Notes/ioport-reproducer/main.py", line 36, in <module>
#     platform.build(top, do_program=False)
#     ~~~~~~~~~~~~~~^^^^^^^^^^^^^^^^^^^^^^^
#   File "/Users/jeanthomas/Documents/Notes/ioport-reproducer/.venv/lib/python3.14/site-packages/amaranth/build/plat.py", line 116, in build
#     plan = self.prepare(elaboratable, name, **kwargs)
#   File "/Users/jeanthomas/Documents/Notes/ioport-reproducer/.venv/lib/python3.14/site-packages/amaranth/build/plat.py", line 176, in prepare
#     return self.toolchain_prepare(self._design, name, **kwargs)
#            ~~~~~~~~~~~~~~~~~~~~~~^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
#   File "/Users/jeanthomas/Documents/Notes/ioport-reproducer/.venv/lib/python3.14/site-packages/amaranth/build/plat.py", line 435, in toolchain_prepare
#     render(content_tpl, origin=content_tpl))
#     ~~~~~~^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
#   File "/Users/jeanthomas/Documents/Notes/ioport-reproducer/.venv/lib/python3.14/site-packages/amaranth/build/plat.py", line 416, in render
#     return compiled.render({
#            ~~~~~~~~~~~~~~~^^
#         "name": name,
#         ^^^^^^^^^^^^^
#     ...<11 lines>...
#         "autogenerated": autogenerated,
#         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
#     })
#     ^^
#   File "/Users/jeanthomas/Documents/Notes/ioport-reproducer/.venv/lib/python3.14/site-packages/jinja2/environment.py", line 1295, in render
#     self.environment.handle_exception()
#     ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~^^
#   File "/Users/jeanthomas/Documents/Notes/ioport-reproducer/.venv/lib/python3.14/site-packages/jinja2/environment.py", line 942, in handle_exception
#     raise rewrite_traceback_stack(source=source)
#   File "<template>", line 2, in top-level template code
#   File "/Users/jeanthomas/Documents/Notes/ioport-reproducer/.venv/lib/python3.14/site-packages/amaranth/build/plat.py", line 181, in iter_port_constraints_bits
#     yield name, port.metadata[0].name, port.metadata[0].attrs
#                 ^^^^^^^^^^^^^^^^^^^^^
# AttributeError: 'NoneType' object has no attribute 'name'


class TangMega138kProDockPlatform(GowinPlatform):
    part          = "GW5AST-LV138FPG676AC1/I0"
    family        = "GW5AST-138B"
    device        = None
    default_clk   = "clk50"

    resources     = [
        Resource("clk50", 0, Pins("P16", dir="i"),
                 Clock(50e6), Attrs(IO_TYPE="LVCMOS33")),
    ]
    connectors    = []

    def iter_port_constraints_bits(self):
        for name, port, _dir in self._design.ports:
            if len(port) == 1:
                if port.metadata[0] is None:
                    continue
                yield name, port.metadata[0].name, port.metadata[0].attrs
            else:
                for bit, meta in enumerate(port.metadata):
                    if meta is None:
                        continue
                    yield f"{name}[{bit}]", meta.name, meta.attrs


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

        my_port = IOPort(1, name="my_port")

        m.submodules.blackbox = Instance("blackbox",
            io_port=my_port)

        return m


if __name__ == '__main__':
    top = Top()
    platform = TangMega138kProDockPlatform(toolchain='Gowin')
    platform.build(top, do_program=False)