Two layer coil gen works with arcs!

1 files changed, 255 insertions, 74 deletions

diff --git a/twisted_coil_gen_twolayer.py b/twisted_coil_gen_twolayer.py
index 574b8b8..a4bb653 100644
--- a/twisted_coil_gen_twolayer.py
+++ b/twisted_coil_gen_twolayer.py
@@ -7,6 +7,7 @@ from math import *
 from pathlib import Path
 from itertools import cycle
 from scipy.constants import mu_0
+import matplotlib as mpl
 
 from gerbonara.cad.kicad import pcb as kicad_pcb
 from gerbonara.cad.kicad import footprints as kicad_fp
@@ -87,59 +88,161 @@ def svg_file(fn, stuff, vbw, vbh, vbx=0, vby=0):
 
         f.write('</svg>\n')
 
+
+# https://en.wikipedia.org/wiki/Farey_sequence#Next_term
+def farey_sequence(n: int, descending: bool = False) -> None:
+    """Print the n'th Farey sequence. Allow for either ascending or descending."""
+    a, b, c, d = 0, 1, 1, n
+    if descending:
+        a, c = 1, n - 1
+    #print(f"{a}/{b}")
+    yield a, b
+
+    while c <= n and not descending or a > 0 and descending:
+        k = (n + b) // d
+        a, b, c, d = c, d, k * c - a, k * d - b
+        #print(f"{a}/{b}")
+        yield a, b
+
+
+def divisors(n, max_b=10):
+    for a, b in farey_sequence(n):
+        if a == n and b < max_b:
+            yield b
+        if b == n and a < max_b:
+            yield a
+
+
+def print_valid_twists(ctx, param, value):
+    if not value or ctx.resilient_parsing:
+        return
+
+    print(f'Valid twist counts for {value} turns:', file=sys.stderr)
+    for d in divisors(value, value):
+        print(f'  {d}', file=sys.stderr)
+
+    click.echo()
+    ctx.exit()
+
+
 @click.command()
 @click.argument('outfile', required=False, type=click.Path(writable=True, dir_okay=False, path_type=Path))
 @click.option('--footprint-name', help="Name for the generated footprint. Default: Output file name sans extension.")
-@click.option('--target-layers', default='F.Cu,B.Cu', help="Target KiCad layers for the generated footprint. Default: F.Cu,B.Cu.")
+@click.option('--layer-pair', default='F.Cu,B.Cu', help="Target KiCad layer pair for the generated footprint, comma-separated. Default: F.Cu/B.Cu.")
 @click.option('--turns', type=int, default=5, help='Number of turns')
-@click.option('--diameter', type=float, default=50, help='Outer diameter [mm]')
-@click.option('--trace-width', type=float, default=0.15)
+@click.option('--outer-diameter', type=float, default=50, help='Outer diameter [mm]')
+@click.option('--inner-diameter', type=float, default=25, help='Inner diameter [mm]')
+@click.option('--trace-width', type=float, default=None)
 @click.option('--via-diameter', type=float, default=0.6)
 @click.option('--via-drill', type=float, default=0.3)
+@click.option('--via-offset', type=float, default=None, help='Radially offset vias from trace endpoints [mm]')
 @click.option('--keepout-zone/--no-keepout-zone', default=True, help='Add a keepout are to the footprint (default: yes)')
 @click.option('--keepout-margin', type=float, default=5, help='Margin between outside of coil and keepout area (mm, default: 5)')
-@click.option('--num-twists', type=int, default=1, help='Number of twists per revolution (default: 1)')
-@click.option('--clearance', type=float, default=0.15)
+@click.option('--twists', type=int, default=1, help='Number of twists per revolution. Note that this number must be co-prime to the number of turns. Run with --show-twists to list valid values. (default: 1)')
+@click.option('--show-twists', callback=print_valid_twists, expose_value=False, type=int, is_eager=True, help='Calculate and show valid --twists counts for the given number of turns. Takes the number of turns as a value.')
+@click.option('--clearance', type=float, default=None)
+@click.option('--arc-tolerance', type=float, default=0.02)
 @click.option('--clipboard/--no-clipboard', help='Use clipboard integration (requires wl-clipboard)')
 @click.option('--counter-clockwise/--clockwise', help='Direction of generated spiral. Default: clockwise when wound from the inside.')
-def generate(outfile, turns, diameter, via_diameter, via_drill, trace_width, clearance, footprint_name, target_layers,
-             num_twists, clipboard, counter_clockwise, keepout_zone, keepout_margin):
+@click.version_option()
+def generate(outfile, turns, outer_diameter, inner_diameter, via_diameter, via_drill, via_offset, trace_width, clearance,
+             footprint_name, layer_pair, twists, clipboard, counter_clockwise, keepout_zone, keepout_margin,
+             arc_tolerance):
     if 'WAYLAND_DISPLAY' in os.environ:
         copy, paste, cliputil = ['wl-copy'], ['wl-paste'], 'xclip'
     else:
         copy, paste, cliputil = ['xclip', '-i', '-sel', 'clipboard'], ['xclip', '-o', '-sel' 'clipboard'], 'wl-clipboard'
 
+    if gcd(twists, turns) != 1:
+        raise click.ClickException('For the geometry to work out, the --twists parameter must be co-prime to --turns, i.e. the two must have 1 as their greatest common divisor. You can print valid values for --twists by running this command with --show-twists [turns number].')
+
+    outer_radius = outer_diameter/2
+    inner_radius = inner_diameter/2
+    turns_per_layer = turns/2
+
+    sweeping_angle = 2*pi * turns_per_layer / twists
+    spiral_pitch = (outer_radius-inner_radius) / turns_per_layer
+    c1 = inner_radius
+    c2 = inner_radius + spiral_pitch
+    alpha1 = atan((outer_radius - inner_radius) / sweeping_angle / c1)
+    alpha2 = atan((outer_radius - inner_radius) / sweeping_angle / c2)
+    alpha = (alpha1+alpha2)/2
+    projected_spiral_pitch = spiral_pitch*cos(alpha)
+
+    if trace_width is None and clearance is None:
+        trace_width = 0.15
+        print(f'Warning: Defaulting to {trace_width:.2f} mm trace width.', file=sys.stderr)
+
+    if trace_width is None:
+        if clearance > projected_spiral_pitch:
+            raise click.ClickException(f'Error: Given clearance of {clearance:.2f} mm is larger than the projected spiral pitch of {projected_spiral_pitch:.2f} mm. Reduce clearance or increase the size of the coil.')
+        trace_width = projected_spiral_pitch - clearance
+        print(f'Calculated trace width for {clearance:.2f} mm clearance is {trace_width:.2f} mm.', file=sys.stderr)
+
+    elif clearance is None:
+        if trace_width > projected_spiral_pitch:
+            raise click.ClickException(f'Error: Given trace width of {trace_width:.2f} mm is larger than the projected spiral pitch of {projected_spiral_pitch:.2f} mm. Reduce clearance or increase the size of the coil.')
+        clearance = projected_spiral_pitch - trace_width
+        print(f'Calculated clearance for {trace_width:.2f} mm trace width is {clearance:.2f} mm.', file=sys.stderr)
+
+    else:
+        if trace_width > projected_spiral_pitch:
+            raise click.ClickException(f'Error: Given trace width of {trace_width:.2f} mm is larger than the projected spiral pitch of {projected_spiral_pitch:.2f} mm. Reduce clearance or increase the size of the coil.')
+        clearance_actual = projected_spiral_pitch - trace_width
+        if clearance_actual < clearance:
+            raise click.ClickException(f'Error: Actual clearance for {trace_width:.2f} mm trace is {clearance_actual:.2f} mm, which is lower than the given clearance of {clearance:.2f} mm.')
+
+    if via_diameter < trace_width:
+        print(f'Clipping via diameter from {via_diameter:.2f} mm to trace width of {trace_width:.2f} mm.', file=sys.stderr)
+        via_diameter = trace_width
+
+    inner_via_ring_radius = inner_radius - via_offset
+    print(f'{inner_radius=} {via_offset=} {via_diameter=}', file=sys.stderr)
+    inner_via_angle = 2*asin((via_diameter + clearance)/2 / inner_via_ring_radius)
+
+    outer_via_ring_radius = outer_radius + via_offset
+    outer_via_angle = 2*asin((via_diameter + clearance)/2 / outer_via_ring_radius)
+
+    print(f'Inner via ring @ {inner_via_ring_radius:.2f} mm (from {inner_radius:.2f} mm)', file=sys.stderr)
+    print(f'    {degrees(inner_via_angle):.1f} deg / via', file=sys.stderr)
+    print(f'Outer via ring @ {outer_via_ring_radius:.2f} mm (from {outer_radius:.2f} mm)', file=sys.stderr)
+    print(f'    {degrees(outer_via_angle):.1f} deg / via', file=sys.stderr)
+
+    if inner_via_angle*twists > 2*pi:
+        min_dia = 2*((via_diameter + clearance) / (2*sin(pi / twists)) + via_offset)
+        raise click.ClickException(f'Error: Overlapping vias in inner via ring. Calculated minimum inner diameter is {min_dia:.2f} mm.')
 
     pitch = clearance + trace_width
-    target_layers = [name.strip() for name in target_layers.split(',')]
-    via_diameter = max(trace_width, via_diameter)
+    t, _, b = layer_pair.partition(',')
+    layer_pair = (t.strip(), b.strip())
     rainbow = '#817 #a35 #c66 #e94 #ed0 #9d5 #4d8 #2cb #0bc #09c #36b #639'.split()
     rainbow = rainbow[2::3] + rainbow[1::3] + rainbow[0::3]
-    out_paths = [SVGPath(fill='none', stroke=rainbow[i%len(rainbow)], stroke_width=trace_width, stroke_linejoin='round', stroke_linecap='round') for i in range(len(target_layers))]
+    n = 5
+    rainbow = rainbow[n:] + rainbow[:n]
+    out_paths = []
     svg_stuff = [*out_paths]
 
 
     # See https://coil32.net/pcb-coil.html for details
 
-    d_inside  = diameter - 2*(pitch*turns - clearance)
-    d_avg = (diameter + d_inside)/2
-    phi = (diameter - d_inside) / (diameter + d_inside)
+    d_avg = (outer_diameter + inner_diameter)/2
+    phi = (outer_diameter - inner_diameter) / (outer_diameter + inner_diameter)
     c1, c2, c3, c4 = 1.00, 2.46, 0.00, 0.20
     L = mu_0 * turns**2 * d_avg*1e3 * c1 / 2 * (log(c2/phi) + c3*phi + c4*phi**2)
-    print(f'Outer diameter: {diameter:g} mm', file=sys.stderr)
+    print(f'Outer diameter: {outer_diameter:g} mm', file=sys.stderr)
     print(f'Average diameter: {d_avg:g} mm', file=sys.stderr)
-    print(f'Inner diameter: {d_inside:g} mm', file=sys.stderr)
+    print(f'Inner diameter: {inner_diameter:g} mm', file=sys.stderr)
     print(f'Fill factor: {phi:g}', file=sys.stderr)
     print(f'Approximate inductance: {L:g} µH', file=sys.stderr)
 
 
-    make_pad = lambda num, x, y: kicad_fp.Pad(
+    make_pad = lambda num, layer, x, y: kicad_fp.Pad(
             number=str(num),
             type=kicad_fp.Atom.smd,
             shape=kicad_fp.Atom.circle,
             at=kicad_fp.AtPos(x=x, y=y),
             size=kicad_fp.XYCoord(x=trace_width, y=trace_width),
-            layers=[target_layer],
+            layers=layer,
             clearance=clearance,
             zone_connect=0)
 
@@ -149,9 +252,9 @@ def generate(outfile, turns, diameter, via_diameter, via_drill, trace_width, cle
                 layer=layer, 
                 stroke=kicad_fp.Stroke(width=trace_width))
 
-    make_arc = lambda x1, y1, x2, y2, xc, yc, layer: kicad_fp.Arc(
+    make_arc = lambda x1, y1, x2, y2, xm, ym, layer: kicad_fp.Arc(
                 start=kicad_fp.XYCoord(x=x1, y=y1),
-                mid=kicad_fp.XYCoord(x=xc, y=yc),
+                mid=kicad_fp.XYCoord(x=xm, y=ym),
                 end=kicad_fp.XYCoord(x=x2, y=y2),
                 layer=layer, 
                 stroke=kicad_fp.Stroke(width=trace_width))
@@ -170,16 +273,40 @@ def generate(outfile, turns, diameter, via_diameter, via_drill, trace_width, cle
     pads = []
     lines = []
     arcs = []
-    turns_per_layer = ceil((turns-1) / len(target_layers))
-    print(f'Splitting {turns} turns into {len(target_layers)} layers using {turns_per_layer} turns per layer plus one weaving turn.', file=sys.stderr)
-    sector_angle = 2*pi / turns_per_layer
-    ### DELETE THIS:
-    d_inside = diameter/2 # FIXME DEBUG
-    ###
-
-    def do_spiral(path, r1, r2, a1, a2, layer, fn=64):
+
+    def arc_approximate(points, layer, tolerance=0.02, level=0):
+        indent = '    ' * level
+        #print(f'{indent}arc_approximate {len(points)=}', file=sys.stderr)
+        if len(points) < 3:
+            raise ValueError()
+
+        i_mid = len(points)//2
+
+        x0, y0 = points[0]
+        x1, y1 = points[i_mid]
+        x2, y2 = points[-1]
+
+        if len(points) < 5:
+            #print(f'{indent} -> interp last points', file=sys.stderr)
+            yield make_arc(x0, y0, x2, y2, x1, y1, layer)
+
+        # https://stackoverflow.com/questions/56224824/how-do-i-find-the-circumcenter-of-the-triangle-using-python-without-external-lib
+        d = 2 * (x0 * (y2 - y1) + x2 * (y1 - y0) + x1 * (y0 - y2))
+        cx = ((x0 * x0 + y0 * y0) * (y2 - y1) + (x2 * x2 + y2 * y2) * (y1 - y0) + (x1 * x1 + y1 * y1) * (y0 - y2)) / d
+        cy = ((x0 * x0 + y0 * y0) * (x1 - x2) + (x2 * x2 + y2 * y2) * (x0 - x1) + (x1 * x1 + y1 * y1) * (x2 - x0)) / d
+        r = dist((cx, cy), (x1, y1))
+        if any(abs(dist((px, py), (cx, cy)) - r) > tolerance for px, py in points):
+            #print(f'{indent} -> split', file=sys.stderr)
+            yield from arc_approximate(points[:i_mid+1], layer, tolerance, level+1)
+            yield from arc_approximate(points[i_mid:], layer, tolerance, level+1)
+
+        else:
+            yield make_arc(x0, y0, x2, y2, x1, y1, layer)
+            #print(f'{indent} -> good fit', file=sys.stderr)
+
+    def do_spiral(layer, r1, r2, a1, a2, start_frac, end_frac, fn=64):
+        fn = ceil(fn * (a2-a1)/(2*pi))
         x0, y0 = cos(a1)*r1, sin(a1)*r1
-        path.move(x0, y0)
         direction = '↓' if r2 < r1 else '↑'
         dr = 3 if r2 < r1 else -3
         label = f'{direction} {degrees(a1):.0f}'
@@ -187,64 +314,118 @@ def generate(outfile, turns, diameter, via_diameter, via_drill, trace_width, cle
                              [label],
                              x=str(x0 + cos(a1)*dr),
                              y=str(y0 + sin(a1)*dr),
-                             style=f'font: 1px bold sans-serif; fill: {path.attrs["stroke"]}'))
+                             text_anchor='middle',
+                             style=f'font: 1px bold sans-serif; fill: {rainbow[layer%len(rainbow)]}'))
 
+        xn, yn = x0, y0
+        points = [(x0, y0)]
         for i in range(fn+1):
+            r, g, b, _a = mpl.cm.plasma(start_frac + (end_frac - start_frac)/fn * (i + 0.5))
+            path = SVGPath(fill='none', stroke=f'#{round(r*255):02x}{round(g*255):02x}{round(b*255):02x}', stroke_width=trace_width, stroke_linejoin='round', stroke_linecap='round')
+            svg_stuff.append(path)
+            xp, yp = xn, yn
             r = r1 + i*(r2-r1)/fn
             a = a1 + i*(a2-a1)/fn
             xn, yn = cos(a)*r, sin(a)*r
+            path.move(xp, yp)
             path.line(xn, yn)
+            points.append((xn, yn))
+            #lines.append(make_line(xp, yp, xn, yn, layer_pair[layer]))
+
+        arcs.extend(arc_approximate(points, layer_pair[layer], arc_tolerance))
 
         svg_stuff.append(Tag('text',
                              [label],
                              x=str(xn + cos(a2)*-dr),
                              y=str(yn + sin(a2)*-dr + 1.2),
-                             style=f'font: 1px bold sans-serif; fill: {path.attrs["stroke"]}'))
-
-
-    print(f'{turns=} {turns_per_layer=} {len(target_layers)=}', file=sys.stderr)
-
-    start_radius = d_inside/2
-    end_radius = diameter/2
-
-    inner_via_ring_radius = start_radius - via_diameter/2
-    inner_via_angle = 2*asin(via_diameter/2 / inner_via_ring_radius)
-
-    outer_via_ring_radius = end_radius + via_diameter/2
-    outer_via_angle = 2*asin(via_diameter/2 / outer_via_ring_radius)
-    print(f'inner via ring @ {inner_via_ring_radius:.2f} mm (from {start_radius:.2f} mm)', file=sys.stderr)
-    print(f'    {degrees(inner_via_angle):.1f} deg / via', file=sys.stderr)
-    print(f'outer via ring @ {outer_via_ring_radius:.2f} mm (from {end_radius:.2f} mm)', file=sys.stderr)
-    print(f'    {degrees(outer_via_angle):.1f} deg / via', file=sys.stderr)
-
-    for n in range(turns-1):
-        layer_n = n % len(target_layers)
-        layer = target_layers[layer_n]
-        layer_turn = floor(n / len(target_layers))
-        print(f'    {layer_n=} {layer_turn=}', file=sys.stderr)
-
-        start_angle = sector_angle * (layer_turn - layer_n / len(target_layers))
-        end_angle = start_angle + (turns_per_layer + 1/len(target_layers)) * sector_angle
-
-        if layer_n % 2 == 1:
-            start_radius, end_radius = end_radius, start_radius
-
-        do_spiral(out_paths[layer_n], start_radius, end_radius, start_angle, end_angle, layer_n)
+                             text_anchor='middle',
+                             style=f'font: 1px bold sans-serif; fill: {rainbow[layer%len(rainbow)]}'))
+
+        return (x0, y0), (xn, yn)
+
+    if via_offset is None:
+        via_offset = max(0, (via_diameter-trace_width)/2)
+        print(f'Autocalculated {via_offset=}', file=sys.stderr)
+
+    sector_angle = 2*pi / twists
+    total_angle = twists*2*sweeping_angle
+
+    inverse = {}
+    for i in range(twists):
+        #print(i, i*turns % twists, file=sys.stderr)
+        inverse[i*turns%twists] = i
+
+    svg_vias = []
+    for i in range(twists):
+        start_angle = i*sector_angle
+        fold_angle = start_angle + sweeping_angle
+        end_angle = fold_angle + sweeping_angle
+
+        x = inverse[i]*floor(2*sweeping_angle / (2*pi)) * 2*pi
+        (x0, y0), (xn, yn) = do_spiral(0, outer_radius, inner_radius, start_angle, fold_angle, (x + start_angle)/total_angle, (x + fold_angle)/total_angle)
+        do_spiral(1, inner_radius, outer_radius, fold_angle, end_angle, (x + fold_angle)/total_angle, (x + end_angle)/total_angle)
+
+        xv, yv = inner_via_ring_radius*cos(fold_angle), inner_via_ring_radius*sin(fold_angle)
+        pads.append(make_via(xv, yv, layer_pair))
+        if via_offset > 0:
+            lines.append(make_line(xn, yn, xv, yv, layer_pair[0]))
+            lines.append(make_line(xn, yn, xv, yv, layer_pair[1]))
+        svg_vias.append(Tag('circle', cx=xv, cy=yv, r=via_diameter/2, stroke='none', fill='white'))
+        svg_vias.append(Tag('circle', cx=xv, cy=yv, r=via_drill/2, stroke='none', fill='black'))
+
+        if i > 0:
+            xv, yv = outer_via_ring_radius*cos(start_angle), outer_via_ring_radius*sin(start_angle)
+            pads.append(make_via(xv, yv, layer_pair))
+            if via_offset > 0:
+                lines.append(make_line(x0, y0, xv, yv, layer_pair[0]))
+                lines.append(make_line(x0, y0, xv, yv, layer_pair[1]))
+            svg_vias.append(Tag('circle', cx=xv, cy=yv, r=via_diameter/2, stroke='none', fill='white'))
+            svg_vias.append(Tag('circle', cx=xv, cy=yv, r=via_drill/2, stroke='none', fill='black'))
+
+    pads.append(make_pad(1, [layer_pair[0]], outer_radius, 0))
+    pads.append(make_pad(2, [layer_pair[1]], outer_radius, 0))
+
+    svg_stuff += svg_vias
+
+    svg_stuff.append(Tag('path', d=f'M {inner_radius} 0 L {outer_radius} 0', stroke=rainbow[n+1], fill='none',
+                         stroke_width='0.05mm', stroke_linecap='round'))
+    ntraces = int(turns_per_layer)+1
+    alpha = [0] * ntraces
+    for i in range(ntraces):
+        c = inner_radius + (outer_radius-inner_radius) / turns_per_layer * i
+        #dalpha = dy / c
+        #dx / dalpha = (outer_radius - inner_radius) / sweeping_angle
+        #c * (dx / dy) = (outer_radius - inner_radius) / sweeping_angle
+        #dx / dy = (outer_radius - inner_radius) / sweeping_angle / c
+        dx = (outer_radius - inner_radius) / sweeping_angle / c
+        alpha[i] = atan(dx)
+        dy = 0.3
+        dx *= dy
+        r = trace_width/2 / cos(alpha[i])
+        svg_stuff.append(Tag('path', d=f'M {c-r+dx} {-dy} L {c-r-dx} {dy}', stroke=rainbow[n+1], fill='none',
+                             stroke_width='0.05mm', stroke_linecap='round'))
+        svg_stuff.append(Tag('path', d=f'M {c+r+dx} {-dy} L {c+r-dx} {dy}', stroke=rainbow[n+1], fill='none',
+                             stroke_width='0.05mm', stroke_linecap='round'))
+
+        #print(f'spiral angle {degrees(alpha[i]):.2f}', file=sys.stderr)
+
+    for i, (a1, a2) in enumerate(zip(alpha[::-1], alpha[1::])):
+        amean = (a2+a1)/2
+        pitch = (outer_radius - inner_radius) / turns_per_layer
+        clearance = pitch - trace_width
+        clearance *= cos(amean)
+
+        x, y = inner_radius + (i + 1/2)*pitch, -0.5
+        svg_stuff.append(Tag('text',
+                             [f'{clearance:.5f}mm'],
+                             x=x,
+                             y=y,
+                             text_anchor='start',
+                             transform=f'rotate(-45 {x} {y})',
+                             style=f'font: 1px bold sans-serif; fill: {rainbow[n+1]}'))
 
     svg_file('/tmp/test.svg', svg_stuff, 100, 100, -50, -50)
 
-    if counter_clockwise:
-        for p in pads:
-            p.at.y = -p.at.y
-
-        for l in lines:
-            l.start.y = -l.start.y
-            l.end.y = -l.end.y
-
-        for a in arcs:
-            a.start.y = -a.start.y
-            a.end.y = -a.end.y
-
     if footprint_name:
         name = footprint_name
     elif outfile:
@@ -253,7 +434,7 @@ def generate(outfile, turns, diameter, via_diameter, via_drill, trace_width, cle
         name = 'generated_coil'
 
     if keepout_zone:
-        r = diameter/2 + keepout_margin
+        r = outer_diameter/2 + keepout_margin
         tol = 0.05 # mm
         n = ceil(pi / acos(1 - tol/r))
         pts = [(r*cos(a*2*pi/n), r*sin(a*2*pi/n)) for a in range(n)]
@@ -269,7 +450,7 @@ def generate(outfile, turns, diameter, via_diameter, via_drill, trace_width, cle
             name=name,
             generator=kicad_fp.Atom('GerbonaraTwistedCoilGenV1'),
             layer='F.Cu',
-            descr=f"{turns} turn {diameter:.2f} mm diameter twisted coil footprint, inductance approximately {L:.6f} µH. Generated by gerbonara'c Twisted Coil generator, version {__version__}.",
+            descr=f"{turns} turn {outer_diameter:.2f} mm diameter twisted coil footprint, inductance approximately {L:.6f} µH. Generated by gerbonara'c Twisted Coil generator, version {__version__}.",
             clearance=clearance,
             zone_connect=0,
             lines=lines,