sandTable/software/sandtable/config.py

"""Machine settings. Defaults below; sandtable.toml (next to the software folder's README) overrides them."""
import copy
import os
import tomllib

HERE = os.path.dirname(os.path.abspath(__file__))
DEFAULT_PATH = os.path.join(os.path.dirname(HERE), 'sandtable.toml')

DEFAULTS = {
    'serial': {
        'port': 'auto',            # 'auto' picks the only Arduino / USB-serial port, or e.g. '/dev/ttyACM0'
        'baud': 115200,
    },
    'controller': {
        'type': 'grbl',            # 'grbl' (Arduino Uno + CNC shield) or 'fluidnc' (the custom ESP32 board)
    },
    'machine': {
        'rho_max_mm': 133.0,       # ball reach from the centre (design: rho 0-133 mm)
        'rho_min_mm': 3.0,         # patterns stay this far out: 1 mm past where the home switch trips
                                   # (homing.switch_rho_mm), so they never press it. A press while a
                                   # pattern runs then means the carriage lost its place: it stops at once.
        'theta_steps_per_deg': 71.111,   # 200 steps x 32 microsteps x 80T/20T / 360
        'rho_steps_per_mm': 160.0,       # 200 x 32 / (20T GT2 = 40 mm)
        'invert_theta': False,     # flip if patterns come out mirrored (set by `test`)
        'theta_offset_deg': 0.0,   # rotate every pattern by this much
    },
    'motion': {
        'ball_speed_mm_s': 25.0,   # drawing speed of the ball across the sand
        'motors_off_when_done': True,   # switch the motors off when the designs are done or stopped
                                        # (quiet, cool); the next design homes first
        'max_theta_deg_s': 60.0,   # arm spin limit (10 rpm)
        'max_rho_mm_s': 25.0,      # carriage limit
        'theta_accel_deg_s2': 120.0,
        'rho_accel_mm_s2': 100.0,
        'max_segment_mm': 1.5,     # long moves are split so the speed stays even
        'max_segment_deg': 3.0,
        'min_segment_mm': 0.3,     # closer points are merged (very dense .thr files)
    },
    'homing': {
        'seek_mm_s': 6.0,
        'feed_mm_s': 1.0,
        'pulloff_mm': 2.0,
        'switch_rho_mm': 2.0,      # rho where the switch trips; Y0 is the centre
        'max_travel_mm': 145.0,
    },
    'erase': {
        'enabled': True,
        'pitch_mm': 7.0,           # spiral spacing; a bit less than the 9.5 mm ball
        'speed_mm_s': 35.0,
    },
}

# GRBL settings `setup` writes to the Uno (X = theta in degrees, Y = rho in mm)
def grbl_settings(cfg):
    m, mo = cfg['machine'], cfg['motion']
    return {
        '$0': '10',          # step pulse, us (DRV8825 needs 1.9)
        '$1': '255',         # keep the motors powered between moves, so the arm can't drift
        '$2': '0',
        '$4': '0',
        '$5': '0',           # limit pin: switch closes to GND, internal pull-up
        '$10': '1',          # status reports show machine position
        '$11': '0.010',
        '$13': '0',
        '$20': '0',          # no soft limits (theta is unlimited)
        '$21': '0',          # no GRBL hard limits: homing presses the switch on purpose. This program
                             # watches the switch while patterns run and stops the machine instead.
        '$22': '0',          # GRBL's own homing off; this program homes rho itself
        '$100': f"{m['theta_steps_per_deg']:.3f}",
        '$101': f"{m['rho_steps_per_mm']:.3f}",
        '$110': f"{mo['max_theta_deg_s'] * 60:.0f}",
        '$111': f"{mo['max_rho_mm_s'] * 60:.0f}",
        '$120': f"{mo['theta_accel_deg_s2']:.0f}",
        '$121': f"{mo['rho_accel_mm_s2']:.0f}",
    }


def _merge(base, over):
    for k, v in over.items():
        if isinstance(v, dict) and isinstance(base.get(k), dict):
            _merge(base[k], v)
        else:
            base[k] = v
    return base


def load(path=None):
    cfg = copy.deepcopy(DEFAULTS)
    path = path or DEFAULT_PATH
    if os.path.exists(path):
        with open(path, 'rb') as f:
            _merge(cfg, tomllib.load(f))
    cfg['_path'] = path
    return cfg


def set_value(path, section, key, value):
    """Set one value in the TOML file, keeping the rest of the file as written."""
    lines = open(path).read().splitlines() if os.path.exists(path) else []
    val = ('true' if value else 'false') if isinstance(value, bool) else (
        f'"{value}"' if isinstance(value, str) else repr(value))
    out, in_sec, done = [], False, False
    for ln in lines:
        s = ln.strip()
        if s.startswith('['):
            if in_sec and not done:
                out.append(f'{key} = {val}')
                done = True
            in_sec = s == f'[{section}]'
        elif in_sec and s.split('=')[0].strip() == key:
            ln, done = f'{key} = {val}', True
        out.append(ln)
    if not done:
        if not in_sec:
            out += ['', f'[{section}]']
        out.append(f'{key} = {val}')
    with open(path, 'w') as f:
        f.write('\n'.join(out) + '\n')