// Skeleton insert for a 250 x 200 x 30 mm photo frame: holds the Planar EL512.256-H
// near the top and a Wemos D1 mini ESP32 below it, visible through the glass.
//
// Panel dimensions are from the datasheet (docs/datasheet, Table 9, Fig. 7), which wins
// over anything else here: PCB 233 x 136 mm, depth 16.5 mm, four M3 insert nuts
// (2.5 mm deep) on a 222.4 x 124.0 mm grid, insert nut tops 8.5 mm behind the front.
// The panel is the bare version (no FRA/FRB mounting frame).
//
// Coordinates: X to the right and Y up as seen from the front, Z towards the viewer.
// The part prints as modelled: back face (z = 0) on the bed, no supports.
//
// Stack inside the photo frame, front to back:
//   photo glass | gap | panel (16.5) | >= 5 mm air gap | truss plate | backboard
// The rim touches the glass and the plate touches the backboard, so the backboard
// clamps the whole insert in place.

/* [Photo frame] */
frame_w      = 245;   // inside width of the photo frame
frame_h      = 194;   // inside height
frame_depth  = 30;    // inside depth, glass included
glass_t      = 2;     // photo glass thickness
backboard_t  = 3;     // backboard thickness (keep it, but drill vent holes)
fit          = 0.6;   // total clearance per axis against the frame

/* [Panel, datasheet Table 9 / Fig. 7] */
pcb_w        = 233;
pcb_h        = 136;
panel_d      = 16.5;  // front of panel glass to tallest part on the back
hole_dx      = 222.4; // insert nut grid
hole_dy      = 124.0;
nut_top      = 8.5;   // front of panel to top of the insert nuts
insert_depth = 2.5;   // M3 thread depth in the nuts
air_gap      = 5;     // recommended free space behind the panel
glass_gap    = 0.5;   // photo glass to panel front, so the EL glass is not pressed
top_margin   = 10;    // frame inside top edge to panel PCB top edge

/* [Screws] */
// The heads sit below the back face, so the back stays flat against the backboard.
head_type    = "socket"; // [countersunk:ISO 10642 / DIN 7991 90 degree, socket:ISO 4762]
screw_len    = 0;     // nominal length (countersunk: overall, head included); 0 = longest that fits
screw_engage = 2;     // thread engagement in the insert nut, < insert_depth
m3_clear     = 3.4;
csk_d        = 6.9;   // countersink diameter (M3 head 6.72 max)
socket_d     = 6.2;   // counterbore for a socket head (5.5 max)
socket_h     = 3.0;   // socket head height
hole_slot    = 1.5;   // extra hole length in X to absorb measuring differences

/* [Truss] */
plate_t      = 3;     // plate thickness
wall         = 2;     // rim wall thickness
border       = 7;     // solid band around the edge, rim included
cell         = 26;    // triangle side length
strut        = 3.5;   // strut width
fillet       = 1.2;   // corner rounding inside the cells
standoff_d   = 9;

/* [D1 mini ESP32] */
d1_l         = 39.0;  // along the USB axis
d1_w         = 31.4;
d1_t         = 1.2;   // PCB thickness
d1_glass_gap = 7;     // photo glass to the board's top face (ESP32 module is ~3.2 high)
d1_rot       = 0;     // 0: USB to the right, 180: USB to the left
d1_clear     = 0.3;   // clearance around the board
d1_ledge     = 2;     // seat width under the short ends (the pin rows run along the long sides)
d1_arm_t     = 0.8;   // snap arm thickness (two 0.4 mm perimeters)
d1_arm_l     = 12;    // snap arm free length, root to tip
d1_arm_gap   = 0.5;   // snap arm to the end of the pocket
d1_lip       = 0.8;   // how far the snap lip reaches over the board
d1_lip_w     = 3;     // snap lip length along the arm
d1_usb_w     = 11;    // kept free between the arms at each end for the USB plug
d1_wall      = 1.6;

/* [Preview] */
show_parts   = true;  // ghosts of the panel and the D1 mini (preview only)

$fn = 48;
eps = 0.01;

// ---------- derived ----------
W = frame_w - fit;
H = frame_h - fit;
part_d = frame_depth - glass_t - backboard_t;   // total insert depth

panel_front = part_d - glass_gap;                // z of the panel front
nut_z       = panel_front - nut_top;             // z of the insert nut tops
panel_back  = panel_front - panel_d;             // z of the tallest panel part
csk         = head_type == "countersunk";
// longest standard M3 length whose head stays below the back face
std_len     = [6, 8, 10, 12, 14, 16, 18, 20, 25, 30];
max_len     = nut_z + screw_engage - (csk ? 0.3 : socket_h + 0.2);
fits        = [for (l = std_len) if (l <= max_len) l];
screw       = screw_len > 0 ? screw_len : fits[len(fits) - 1];
head_sink   = nut_z + screw_engage - screw;      // back face to the top of the screw head

pcb_x0 = (W - pcb_w) / 2;
pcb_y1 = H - top_margin;
pcb_y0 = pcb_y1 - pcb_h;
pcb_cx = W / 2;
pcb_cy = (pcb_y0 + pcb_y1) / 2;

holes = [for (sx = [-1, 1], sy = [-1, 1]) [pcb_cx + sx * hole_dx / 2, pcb_cy + sy * hole_dy / 2]];

d1_cx  = W / 2;
d1_cy  = (border + pcb_y0) / 2;
d1_top = part_d - d1_glass_gap;                  // z of the board's top face
d1_seat = d1_top - d1_t;                         // z of the board's bottom face
d1_in_l = d1_l + 2 * d1_clear;
d1_in_w = d1_w + 2 * d1_clear;
d1_flex   = d1_clear + d1_lip;                   // worst-case arm deflection while snapping in
d1_arm_x  = d1_in_l / 2 + d1_arm_gap;            // inner face of the snap arms
d1_x_out  = d1_arm_x + d1_arm_t + d1_flex + 0.4; // outer edge of the slot the arms flex into
d1_root   = d1_in_w / 2 + d1_wall;               // y of the arm roots
d1_tip    = d1_root - d1_arm_l;                  // y of the arm tips
d1_catch  = d1_top + 0.1;                        // z of the underside of the lips
// bending strain at the arm root with the lip pushed fully out
d1_strain = 1.5 * d1_arm_t * d1_flex / pow(d1_arm_l - d1_lip_w / 2, 2);

assert(pcb_x0 >= wall + 1, "panel does not fit the frame width");
assert(pcb_y0 - border >= 2 * (d1_root + d1_wall) + 2, "no room below the panel for the D1 mini");
assert(d1_tip >= d1_usb_w / 2, "snap arms reach into the USB plug's way: shorten d1_arm_l");
assert(d1_strain <= 0.015, str("snap arms strained ", d1_strain * 100, " %, too much for PLA"));
assert(panel_back - plate_t >= air_gap, "less than the recommended air gap behind the panel");
assert(screw_engage < insert_depth, "screw would bottom out in the insert nut");
assert(head_sink >= (csk ? 0.3 : socket_h + 0.2),
       str("screw head would stick out of the back: use M3x", floor(max_len), " or shorter"));
assert(head_sink <= nut_z - 4, "screw_len too short for this stack");

echo(str("Insert depth ", part_d, " mm, air gap behind panel ", panel_back - plate_t,
         " mm, standoff height ", nut_z - plate_t, " mm, use M3x", screw, " ", head_type,
         " (head ", head_sink, " mm below the back face), snap arm strain ",
         round(d1_strain * 1000) / 10, " %"));

// ---------- 2D ----------
module outline() square([W, H]);

module d1_footprint(grow = 0) {
    translate([d1_cx, d1_cy]) rotate(d1_rot)
        square([2 * (d1_x_out + 1 + grow), 2 * (d1_root + d1_wall + grow)], center = true);
}

// Triangle cells; a horizontal strut runs along the panel's bottom edge and a vertex
// sits on the centre line, so the pattern is symmetric.
module tri_cells() {
    h  = cell * sqrt(3) / 2;
    x0 = W / 2 - cell * ceil(W / 2 / cell) - cell;
    y0 = pcb_y0 - h * ceil(pcb_y0 / h) - h;
    for (j = [0 : ceil(H / h) + 2], k = [0 : 2 * ceil(W / cell) + 4]) {
        x = x0 + k * cell / 2;
        y = y0 + j * h;
        up = (k + j) % 2 == 0;
        pts = up ? [[x, y], [x + cell, y], [x + cell / 2, y + h]]
                 : [[x, y + h], [x + cell, y + h], [x + cell / 2, y]];
        offset(r = fillet) offset(delta = -(strut / 2 + fillet)) polygon(pts);
    }
}

module plate_2d() {
    difference() {
        outline();
        // the opening drops slivers of cells clipped by the border and the pads
        offset(r = 1.5) offset(delta = -1.5) difference() {
            intersection() {
                offset(delta = -border) outline();
                tri_cells();
            }
            // solid pads under the standoffs and the D1 mini cradle
            for (p = holes) translate(p) circle(d = standoff_d + 8);
            d1_footprint(2);
        }
    }
}

// ---------- 3D ----------
module rim() {
    linear_extrude(part_d) difference() {
        outline();
        offset(delta = -wall) outline();
    }
}

module standoff(p) {
    translate(p) {
        cylinder(d = standoff_d, h = nut_z);
        cylinder(d1 = standoff_d + 6, d2 = standoff_d, h = plate_t + 3);  // base fillet
    }
}

module slot() hull() for (s = [-1, 1]) translate([s * hole_slot / 2, 0, 0]) children();

// Slotted screw hole. Countersunk: the head's top face sits head_sink below the back
// face. Socket head: its bearing face sits head_sink deep, the head in a counterbore.
module screw_cut(p) translate(p) {
    slot() translate([0, 0, -1]) cylinder(d = m3_clear, h = nut_z + 2);
    if (csk) {
        slot() translate([0, 0, -1]) cylinder(d = csk_d, h = head_sink + 1);
        slot() translate([0, 0, head_sink - eps])
            cylinder(d1 = csk_d, d2 = m3_clear, h = (csk_d - m3_clear) / 2);  // 90 degrees
    } else {
        slot() translate([0, 0, -1]) cylinder(d = socket_d, h = head_sink + 1);
    }
}

// Cradle for the D1 mini, board face up towards the glass. It rests on ledges under its
// short ends and four snap arms hold it down; the pin rows hang free over the hollow
// inside. The upper long wall has a slot for the wires to the panel.
//
// The snap arms run along the short ends, anchored at the corners with the lip at the
// free end, and bend sideways: the strain runs along the printed perimeters instead of
// across the layers, so they hold up in PLA. Each arm stands on the bed in a slot through
// the plate. The arms leave d1_usb_w free in the middle of each end for the USB plug.
module d1_place() translate([d1_cx, d1_cy, 0]) rotate(d1_rot) children();
module d1_quadrants() for (mx = [0, 1], my = [0, 1]) mirror([mx, 0, 0]) mirror([0, my, 0]) children();

module d1_cradle() d1_place() {
    difference() {
        union() {
            // long walls, flush with the board's top face
            for (s = [-1, 1]) translate([-d1_in_l / 2, s > 0 ? d1_in_w / 2 : -d1_in_w / 2 - d1_wall, 0])
                cube([d1_in_l, d1_wall, d1_top]);
            // seat ledges under the short ends
            for (s = [-1, 1]) translate([s > 0 ? d1_in_l / 2 - d1_ledge : -d1_in_l / 2, -d1_in_w / 2, 0])
                cube([d1_ledge, d1_in_w, d1_seat]);
            // arm anchors, outside the long walls at the corners
            d1_quadrants() translate([d1_in_l / 2 - 2, d1_root - eps, 0])
                cube([d1_x_out + 1 - (d1_in_l / 2 - 2), d1_wall + eps, d1_top]);
        }
        // wire slot towards the panel
        translate([-10, d1_in_w / 2 - eps, plate_t]) cube([20, d1_wall + 2 * eps, d1_seat - plate_t - 2]);
    }
}

// Slots through the plate that free the arms from everything but their anchors.
module d1_arm_slots() d1_place() d1_quadrants()
    translate([d1_in_l / 2, d1_tip - 0.6, -1]) cube([d1_x_out - d1_in_l / 2, d1_root - d1_tip + 0.6, plate_t + 2]);

// The lip has a 45 degree chamfer underneath across the gap to the pocket, so only the
// catch itself (clearance + d1_lip) is a flat overhang, and a blunt tip.
module d1_arms() d1_place() d1_quadrants() {
    t     = d1_arm_t;
    g     = d1_arm_gap;
    reach = g + d1_clear + d1_lip;              // arm face to lip tip
    tip_h = 0.6;
    translate([d1_arm_x, d1_tip, 0]) cube([t, d1_arm_l + eps, d1_catch]);
    translate([d1_arm_x + t, d1_tip + d1_lip_w, d1_catch]) rotate([90, 0, 0])
        linear_extrude(d1_lip_w) polygon([
            [0, -g], [-t, -g],                  // chamfer starts on the arm face
            [-t - g, 0],                        // 45 degrees across the gap
            [-t - reach, 0],                    // flat catch over the board
            [-t - reach, tip_h],                // blunt tip
            [-t, tip_h + reach],                // 45 degree lead-in
            [0, tip_h + reach]]);
}

module frame() {
    difference() {
        union() {
            linear_extrude(plate_t) plate_2d();
            rim();
            for (p = holes) standoff(p);
            d1_cradle();
        }
        for (p = holes) screw_cut(p);
        d1_arm_slots();
    }
    d1_arms();
}

module ghosts() {
    // panel: PCB and glass block, front at panel_front
    color("dimgray", 0.35) translate([pcb_x0, pcb_y0, panel_back]) cube([pcb_w, pcb_h, panel_d]);
    color("orange", 0.5) translate([pcb_cx - 97.55, pcb_cy - 48.75, panel_front - 0.2]) cube([195.1, 97.5, 0.2]);
    // D1 mini
    color("royalblue", 0.5) translate([d1_cx, d1_cy, d1_seat]) rotate(d1_rot)
        translate([-d1_l / 2, -d1_w / 2, 0]) cube([d1_l, d1_w, d1_t]);
    // photo glass
    color("lightblue", 0.15) translate([0, 0, part_d]) cube([W, H, glass_t]);
}

frame();
if (show_parts && $preview) %ghosts();