esp32-s3-sensor-node/edit_pcb.py

#!/usr/bin/env python3
"""S-expression based PCB editor. Safely replaces nets, board outline, title."""
import re, os

class SExpr:
    """Simple S-expression node."""
    def __init__(self, type_name, children=None, value=None):
        self.type = type_name
        self.children = children or []
        self.value = value  # For leaf nodes: their string content
    
    def __repr__(self):
        if self.children:
            return f'({self.type} {" ".join(repr(c) for c in self.children)})'
        return f'({self.type} {self.value})' if self.value else f'({self.type})'

def parse_sexpr(text, pos=0):
    """Parse S-expression from text, return (node, new_pos)."""
    text = text.strip()
    if pos >= len(text):
        return None, pos
    # Skip whitespace
    while pos < len(text) and text[pos] in ' \t\n\r':
        pos += 1
    if pos >= len(text):
        return None, pos
    
    if text[pos] == '(':
        pos += 1
        # Read first token (type name)
        while pos < len(text) and text[pos] in ' \t\n\r':
            pos += 1
        if pos >= len(text):
            return None, pos
        # Check if it's a quoted string
        if text[pos] == '"':
            end = text.find('"', pos + 1)
            type_name = text[pos:end+1]
            pos = end + 1
        else:
            end = pos
            while end < len(text) and text[end] not in ' \t\n\r()':
                end += 1
            type_name = text[pos:end]
            pos = end
        
        children = []
        while pos < len(text):
            while pos < len(text) and text[pos] in ' \t\n\r':
                pos += 1
            if pos >= len(text):
                break
            if text[pos] == ')':
                pos += 1
                return SExpr(type_name, children), pos
            if text[pos] == '(':
                child, pos = parse_sexpr(text, pos)
                if child:
                    children.append(child)
            elif text[pos] == '"':
                end = text.find('"', pos + 1)
                children.append(SExpr("__str__", value=text[pos:end+1]))
                pos = end + 1
            else:
                end = pos
                while end < len(text) and text[end] not in ' \t\n\r()':
                    end += 1
                children.append(SExpr("__atom__", value=text[pos:end]))
                pos = end
        return SExpr(type_name, children), pos
    
    # Leaf value
    if text[pos] == '"':
        end = text.find('"', pos + 1)
        result = SExpr("__str__", value=text[pos:end+1])
        return result, end + 1
    end = pos
    while end < len(text) and text[end] not in ' \t\n\r()':
        end += 1
    return SExpr("__atom__", value=text[pos:end]), end

def find_first(root, type_name):
    """Find first child with given type name."""
    for c in root.children:
        if c.type == type_name:
            return c
        found = find_first(c, type_name)
        if found:
            return found
    return None

PROJ = os.path.expanduser("~/Documents/KiCad/10.0/esp32-s3-sensor-node")
TEMPLATE = os.path.expanduser(
    "~/Documents/KiCad/10.0/USB_PD_ESP32S3/USB_PD_ESP32S3.kicad_pcb")
PCB = os.path.join(PROJ, "esp32-s3-sensor-node.kicad_pcb")

NETS = ["GND","3V3","VBUS","EN","IO0","IO12","SDA","SCL",
        "USB_D_P","USB_D_N","CC1","CC2","IO2_LED","D1_A","RXD0","TXD0"]

def build():
    content = open(TEMPLATE).read()
    
    # Simple text-based replacement that's safe
    
    # 1. Replace title
    content = re.sub(r'\(title "[^"]*"', '(title "ESP32-S3 Sensor Node"', content)
    
    # 2. Replace date
    content = re.sub(r'\(date "[^"]*"', '(date "2026-06-22"', content)
    
    # 3. Find the nets section and replace it
    net_start = content.find('\n\t(nets')
    if net_start < 0:
        print("ERROR: no nets section")
        return
    
    # Find the closing of nets
    # The structure is: \n\t(nets\n\t\t(net 0 "xxx")\n\t\t...\n\t)
    net_end = content.find('\n\t)', net_start)
    if net_end < 0:
        print("ERROR: no nets close")
        return
    net_end += 3  # include the closing paren
    
    new_nets = '\t(nets\n'
    for i, n in enumerate(NETS):
        new_nets += f'\t\t(net {i} "{n}")\n'
    new_nets += '\t)'
    
    content = content[:net_start] + new_nets + content[net_end:]
    
    # 4. Replace net classes
    # Find first net_class line
    nc_start = content.find('\n\t(net_class')
    if nc_start < 0:
        print("ERROR: no net_class section")
        return
    
    # Find where net classes end (before polygon or first footprint)
    # Find the first line that doesn't start with \t(net_class after nc_start
    nc_end = content.find('\n\t(', nc_start + 50)
    # Make sure it's not a net_class
    while content[nc_end:nc_end+11] == '\n\t(net_class':
        nc_end = content.find('\n\t(', nc_end + 1)
    
    net_class_def = '''\t(net_class "Default" (clearance 0.15) (trace_width 0.2)
\t\t(via_dia 0.6) (via_drill 0.3)
\t\t(add_net "*"))
\t(net_class "POWER" (clearance 0.25) (trace_width 0.5)
\t\t(via_dia 0.8) (via_drill 0.4)
\t\t(add_net "3V3") (add_net "VBUS"))
\t(net_class "USB" (clearance 0.15) (trace_width 0.2)
\t\t(via_dia 0.6) (via_drill 0.3)
\t\t(add_net "USB_D_P") (add_net "USB_D_N"))'''
    
    content = content[:nc_start] + net_class_def + content[nc_end:]
    
    # 5. Replace board outline
    # Find (polygon (layer "Edge.Cuts")
    edge_start = content.find('(layer "Edge.Cuts")')
    if edge_start < 0:
        print("ERROR: no Edge.Cuts polygon")
        return
    
    # Find the beginning of this polygon
    poly_start = content.rfind('(', edge_start - 100, edge_start)
    # Find the end (matching parenthesis)
    depth = 0
    i = poly_start
    while i < len(content):
        if content[i] == '(':
            depth += 1
        elif content[i] == ')':
            depth -= 1
            if depth == 0:
                poly_end = i + 1
                break
        i += 1
    
    new_outline = '''\t(polygon
\t\t(layer "Edge.Cuts")
\t\t(pts
\t\t\t(xy 0 0)
\t\t\t(xy 65 0)
\t\t\t(xy 65 40)
\t\t\t(xy 0 40)))'''
    
    content = content[:poly_start] + new_outline + content[poly_end:]
    
    # 6. Remove all footprints, zones, segments, vias, arcs
    # These are between the net classes and (embedded_fonts no)
    ef_pos = content.find('\t(embedded_fonts no)')
    if ef_pos < 0:
        print("ERROR: no embedded_fonts")
        return
    
    # Find the last net_class or polygon
    last_our = content.find('(xy 0 40)))', poly_start)
    last_our_end = content.find(')', last_our) + 1
    
    # Everything between last_our_end and embedded_fonts needs to go
    content = content[:last_our_end] + '\n' + content[ef_pos:]
    
    with open(PCB, 'w') as f:
        f.write(content)
    print(f"Written: {len(content)} bytes")

if __name__ == "__main__":
    build()