thelio-io-hardware/script/impedance

#!/usr/bin/env python3

from subprocess import check_call

# All units in um

COPPER_OZ = 35.0
MIL = 25.4

CONDUCTOR = "conductor"
INSULATOR = "insulator"

fr4 = {
    "name": "FR4",
    "kind": INSULATOR,
    "thickness": 500.0,
    "er": 4.2,
}

pp1080 = {
    "name": "1080",
    "kind": INSULATOR,
    "thickness": 74.9,
    "er": 4.2,
}

pp2116 = {
    "name": "2116",
    "kind": INSULATOR,
    "thickness": 114.3,
    "er": 4.2,
}

pcie = {
    "name": "PCIe",
    "width": 5.0 * MIL,
    "spacing": 5.0 * MIL,
    "reference": "GND",
}

def conductor(name, thickness=COPPER_OZ, planes=[], tracks=[]):
    return {
        "name": name,
        "kind": CONDUCTOR,
        "thickness": thickness,
        "planes": planes,
        "tracks": tracks,
    }

stackup = [
    conductor("F", thickness=COPPER_OZ/3.0, tracks=[pcie]),
    pp2116,
    conductor("In1", planes=["GND"]),
    fr4,
    conductor("In2", planes=["GND"]),
    pp1080,
    pp1080,
    conductor("In3", thickness=COPPER_OZ/3.0, tracks=[pcie]),
    fr4,
    conductor("In4", planes=["GND", "12V"]),
    pp2116,
    conductor("B", thickness=COPPER_OZ/3.0, tracks=[pcie]),
]

for i, layer in enumerate(stackup):
    if layer["kind"] == CONDUCTOR:
        print("Layer", layer["name"])
        #TODO: Find dielectrics using track reference

        dielectrics = []

        above = {
            "thickness": 0.0,
            "er": None,
        }

        j = i
        while j > 0:
            j -= 1
            other = stackup[j]
            if other["kind"] == INSULATOR:
                above["thickness"] += other["thickness"]
                if above["er"] is None:
                    above["er"] = other["er"]
                elif above["er"] != other["er"]:
                    raise Exception("above.er != other.er")
            else:
                break

        if above["er"] is not None:
            dielectrics.append(above)

        below = {
            "thickness": 0.0,
            "er": None
        }

        j = i + 1
        while j < len(stackup):
            other = stackup[j]
            if other["kind"] == INSULATOR:
                below["thickness"] += other["thickness"]
                if below["er"] is None:
                    below["er"] = other["er"]
                elif below["er"] != other["er"]:
                    raise Exception("below.er != other.er")
            else:
                break
            j += 1

        if below["er"] is not None:
            dielectrics.append(below)

        t = layer["thickness"]
        for track in layer["tracks"]:
            print("  Track", track["name"])
            w = track["width"]
            s = track["spacing"]
            filename = "build/" + layer["name"] + "_" + track["name"] + ".bmp"
            if len(dielectrics) == 1:
                # microstrip
                h = dielectrics[0]["thickness"]
                er2 = dielectrics[0]["er"]
                print(
                    "    Microstrip Coupler",
                    "t", t,
                    "w", w,
                    "s", s,
                    "h", h,
                    "er", er2
                )

                er1 = 1.0
                g = 5 * h # TODO
                check_call([
                    "create_bmp_for_microstrip_coupler",
                    str(w),
                    str(s),
                    str(g),
                    str(h),
                    str(t),
                    str(er1),
                    str(er2),
                    filename
                ])
                check_call([
                    "atlc",
                    "-S",
                    "-d",
                    "ac82ac=" + str(er2),
                    filename
                ])
            elif len(dielectrics) == 2:
                # asymmetric stripline
                er1 = dielectrics[0]["er"]
                h1 = dielectrics[0]["thickness"]
                er2 = dielectrics[1]["er"]
                h2 = dielectrics[1]["thickness"]
                print(
                    "    Asymmetric Stripline Coupler",
                    "t", t,
                    "w", w,
                    "s", s,
                    "h1", h1,
                    "er1", er1,
                    "h2", h2,
                    "er2", er2
                )
                # TODO
            else:
                raise Exception("missing reference")