decode_1wire_json.py

#!/usr/bin/env python3
import json
import sys

if len(sys.argv) != 2:
    print(f"Usage: {sys.argv[0]} dq.json", file=sys.stderr)
    sys.exit(1)

path = sys.argv[1]

# --- 1. Read JSON events ----------------------------------------------------
events = []
with open(path, "r") as f:
    for line in f:
        line = line.strip()
        if not line:
            continue
        events.append(json.loads(line))

if not events:
    print("No events found in file.", file=sys.stderr)
    sys.exit(1)

# --- 2. Extract low pulses (1 -> 0, then 0 -> 1) ----------------------------
pulses = []  # list of (start_time, width)
prev = events[0]

for i in range(1, len(events)):
    cur = events[i]

    # falling edge: 1 -> 0
    if prev["v"] == 1 and cur["v"] == 0:
        start_t = cur["t"]
        # search for next rising edge 0 -> 1
        width = None
        for j in range(i + 1, len(events)):
            nxt = events[j]
            if nxt["v"] == 1:
                width = nxt["t"] - start_t
                break
        if width is not None:
            pulses.append((start_t, width))

    prev = cur

# --- 3. Convert pulse widths to bits ----------------------------------------
bits = []

for start_t, width in pulses:
    # Ignore reset/presence etc. (very long pulses)
    if width <= 10:
        bits.append(1)
    elif 40 <= width <= 80:
        bits.append(0)
    else:
        # probably reset (≈480) or presence (≈150) -> skip
        continue

if not bits:
    print("No data bits found (check thresholds).", file=sys.stderr)
    sys.exit(1)

# --- 4. Group bits into bytes (LSB-first) -----------------------------------
bytes_out = []

for i in range(0, len(bits), 8):
    chunk = bits[i:i+8]
    if len(chunk) < 8:
        break
    val = 0
    for bit_index, b in enumerate(chunk):
        val |= (b & 1) << bit_index  # LSB-first
    bytes_out.append(val)

# --- 5. Print result ---------------------------------------------------------
hex_str = " ".join(f"{b:02x}" for b in bytes_out)
ascii_str = "".join(chr(b) if 32 <= b < 127 else "." for b in bytes_out)

print("Hex bytes:")
print(hex_str)
print("\nASCII (non-printables shown as '.'):")
print(ascii_str)