Added back debug logs to Spoolbuddy test scripts

spoolbuddy/scripts/read_tag.py

@@ -1,23 +1,550 @@
 #!/usr/bin/env python3
-"""PN5180 NFC Tag Reader diagnostic script.
-
-Standalone diagnostic — the PN5180 driver lives in
-spoolbuddy/daemon/pn5180.py and is imported from there.
-
-Supports: Bambu (MIFARE Classic) + NTAG (SpoolEase/OpenPrintTag)
+"""PN5180 NFC tag reader — ported from working Pico firmware (pico-nfc-bridge.ino).
+
+Key learnings from pico-nfc-bridge.ino:
+- Must call setTransceiveMode() before every SEND_DATA
+- waitBusy() must wait for HIGH then LOW (not just LOW)
+- Bambu tags are MIFARE Classic 1K (ISO 14443A), not ISO 15693
+- SPI at 500kHz, 5µs CS setup, 100µs post-CS delay
+- MFC_AUTHENTICATE (0x0C) is a PN5180 host command — Crypto1 handled in hardware
+- HKDF-SHA256 derives per-sector keys from master key + UID
 """
 
-import logging
+import hashlib
+import hmac
+import os
 import sys
 import time
-from pathlib import Path
 
-# Add daemon package to sys.path so we can import the driver
-sys.path.insert(0, str(Path(__file__).resolve().parent.parent))
-from daemon.pn5180 import BAMBU_BLOCKS, PN5180
+import gpiod
+import spidev
+
+
+def _env_int(name: str, default: int) -> int:
+    value = os.environ.get(name)
+    if value is None or value == "":
+        return default
+    try:
+        return int(value)
+    except ValueError:
+        return default
+
+
+BUSY_PIN = _env_int("SPOOLBUDDY_NFC_BUSY_PIN", 25)
+RST_PIN = _env_int("SPOOLBUDDY_NFC_RST_PIN", 24)
+NSS_PIN = _env_int("SPOOLBUDDY_NFC_NSS_PIN", 23)  # Manual CS by default
+SPI_BUS = _env_int("SPOOLBUDDY_NFC_SPI_BUS", 0)
+SPI_DEVICE = _env_int("SPOOLBUDDY_NFC_SPI_DEVICE", 0)
+SPI_SPEED_HZ = _env_int("SPOOLBUDDY_NFC_SPI_SPEED_HZ", 500_000)
+
+# Bambu Lab MIFARE Classic key derivation constants (from pico-nfc-bridge.ino)
+BAMBU_MASTER_KEY = bytes(
+    [
+        0x9A,
+        0x75,
+        0x9C,
+        0xF2,
+        0xC4,
+        0xF7,
+        0xCA,
+        0xFF,
+        0x22,
+        0x2C,
+        0xB9,
+        0x76,
+        0x9B,
+        0x41,
+        0xBC,
+        0x96,
+    ]
+)
+BAMBU_CONTEXT = b"RFID-A\x00"  # 7 bytes including null terminator
+
+# Blocks to read for Bambu tag data
+BAMBU_BLOCKS = [1, 2, 4, 5]
+
+
+def hkdf_derive_keys(uid: bytes) -> bytes:
+    """Derive 96 bytes of MIFARE key material (16 sectors * 6 bytes each).
+
+    Uses HKDF-SHA256 with the Bambu master key as salt and the tag UID as IKM.
+    """
+    # HKDF-Extract: PRK = HMAC-SHA256(salt=master_key, IKM=uid)
+    prk = hmac.new(BAMBU_MASTER_KEY, uid, hashlib.sha256).digest()
+
+    # HKDF-Expand: generate 96 bytes using context "RFID-A\0"
+    okm = b""
+    t = b""
+    counter = 1
+    while len(okm) < 96:
+        t = hmac.new(prk, t + BAMBU_CONTEXT + bytes([counter]), hashlib.sha256).digest()
+        okm += t
+        counter += 1
+    return okm[:96]
+
+
+def get_sector_key(keys: bytes, block: int) -> bytes:
+    """Get the 6-byte key for the sector containing the given block."""
+    sector = block // 4
+    return keys[sector * 6 : sector * 6 + 6]
+
+
+def _find_gpio_chip():
+    for path in ["/dev/gpiochip4", "/dev/gpiochip0"]:
+        try:
+            chip = gpiod.Chip(path)
+            if "pinctrl" in chip.get_info().label:
+                return chip
+            chip.close()
+        except (FileNotFoundError, PermissionError, OSError):
+            continue
+    raise RuntimeError("No GPIO chip")
+
+
+class PN5180:
+    def __init__(self):
+        self._chip = _find_gpio_chip()
+        self._lines = self._chip.request_lines(
+            consumer="pn5180",
+            config={
+                BUSY_PIN: gpiod.LineSettings(direction=gpiod.line.Direction.INPUT),
+                RST_PIN: gpiod.LineSettings(
+                    direction=gpiod.line.Direction.OUTPUT, output_value=gpiod.line.Value.ACTIVE
+                ),
+                NSS_PIN: gpiod.LineSettings(
+                    direction=gpiod.line.Direction.OUTPUT, output_value=gpiod.line.Value.ACTIVE
+                ),
+            },
+        )
+        self._spi = spidev.SpiDev()
+        self._spi.open(SPI_BUS, SPI_DEVICE)
+        self._spi.max_speed_hz = SPI_SPEED_HZ
+        self._spi.mode = 0b00
+        self._spi.no_cs = True
+
+    def close(self):
+        self._spi.close()
+        self._lines.release()
+        self._chip.close()
+
+    def _cs_low(self):
+        self._lines.set_value(NSS_PIN, gpiod.line.Value.INACTIVE)
+        time.sleep(0.000005)  # 5µs setup
+
+    def _cs_high(self):
+        self._lines.set_value(NSS_PIN, gpiod.line.Value.ACTIVE)
+        time.sleep(0.000100)  # 100µs post-CS delay
+
+    def _wait_busy(self, timeout_s=1.0):
+        """Wait for BUSY to go HIGH (processing) then LOW (done) — matches Pico firmware."""
+        deadline = time.monotonic() + min(timeout_s, 0.010)
+        # Wait for BUSY HIGH (PN5180 started processing)
+        while self._lines.get_value(BUSY_PIN) != gpiod.line.Value.ACTIVE:
+            if time.monotonic() > deadline:
+                break  # Timeout waiting for HIGH — command may have processed already
+            time.sleep(0.00001)
+        # Wait for BUSY LOW (PN5180 done)
+        deadline = time.monotonic() + timeout_s
+        while self._lines.get_value(BUSY_PIN) == gpiod.line.Value.ACTIVE:
+            if time.monotonic() > deadline:
+                raise TimeoutError("BUSY timeout")
+            time.sleep(0.0001)
+
+    def _cmd(self, data):
+        self._cs_low()
+        self._spi.xfer2(list(data))
+        self._cs_high()
+        self._wait_busy()
+
+    def _read_response(self, n):
+        self._cs_low()
+        result = self._spi.xfer2([0xFF] * n)
+        self._cs_high()
+        return result
+
+    # -- Register ops --
+
+    def write_reg(self, reg, val):
+        self._cmd([0x00, reg, val & 0xFF, (val >> 8) & 0xFF, (val >> 16) & 0xFF, (val >> 24) & 0xFF])
+
+    def write_reg_or(self, reg, mask):
+        self._cmd([0x01, reg, mask & 0xFF, (mask >> 8) & 0xFF, (mask >> 16) & 0xFF, (mask >> 24) & 0xFF])
+
+    def write_reg_and(self, reg, mask):
+        self._cmd([0x02, reg, mask & 0xFF, (mask >> 8) & 0xFF, (mask >> 16) & 0xFF, (mask >> 24) & 0xFF])
+
+    def read_reg(self, reg):
+        self._cmd([0x04, reg])
+        time.sleep(0.000100)  # Extra 100µs before read
+        return int.from_bytes(self._read_response(4), "little")
+
+    def read_eeprom(self, addr, length):
+        self._cmd([0x07, addr, length])
+        time.sleep(0.000100)
+        return bytes(self._read_response(length))
+
+    # -- Commands --
+
+    def reset(self):
+        self._lines.set_value(RST_PIN, gpiod.line.Value.INACTIVE)
+        time.sleep(0.050)
+        self._lines.set_value(RST_PIN, gpiod.line.Value.ACTIVE)
+        time.sleep(0.100)
+        self._wait_busy(2.0)
+        time.sleep(0.050)
+
+    def load_rf_config(self, tx, rx):
+        self.write_reg(0x03, 0xFFFFFFFF)  # Clear IRQs first
+        time.sleep(0.000100)
+        self._cmd([0x11, tx, rx])
+        time.sleep(0.010)
+
+    def rf_on(self):
+        self._cmd([0x16, 0x00])
+        time.sleep(0.010)
+
+    def rf_off(self):
+        self._cmd([0x17, 0x00])
+        time.sleep(0.005)
+
+    def set_transceive_mode(self):
+        """Set SYSTEM_CONFIG command bits to TRANSCEIVE (0x03) — CRITICAL!"""
+        sys_cfg = self.read_reg(0x00)
+        sys_cfg = (sys_cfg & 0xFFFFFFF8) | 0x03
+        self.write_reg(0x00, sys_cfg)
+
+    def send_data(self, data, valid_bits=0x00):
+        self._cs_low()
+        self._spi.xfer2([0x09, valid_bits] + list(data))
+        self._cs_high()
+        time.sleep(0.000100)
+        self._wait_busy()
+
+    def read_data(self, length):
+        self._cmd([0x0A, 0x00])
+        return bytes(self._read_response(length))
+
+    # -- ISO 14443A --
+
+    def activate_type_a(self):
+        """Full Type A activation: WUPA -> Anticollision -> SELECT. Returns (uid, sak) or None."""
+        # Crypto off, CRC off
+        self.write_reg_and(0x00, 0xFFFFFFBF)
+        self.write_reg_and(0x12, 0xFFFFFFFE)
+        self.write_reg_and(0x19, 0xFFFFFFFE)
+        self.write_reg(0x03, 0xFFFFFFFF)
+
+        # Reset to IDLE then TRANSCEIVE
+        sys_cfg = self.read_reg(0x00)
+        self.write_reg(0x00, sys_cfg & 0xFFFFFFF8)  # IDLE
+        time.sleep(0.001)
+        self.write_reg(0x00, (sys_cfg & 0xFFFFFFF8) | 0x03)  # TRANSCEIVE
+        time.sleep(0.002)
+
+        # WUPA (7-bit)
+        self.send_data([0x52], valid_bits=0x07)
+        time.sleep(0.005)
+
+        rx_status = self.read_reg(0x13)
+        rx_len = rx_status & 0x1FF
+        if rx_len < 2 or rx_len == 511:
+            # Try REQA
+            self.write_reg(0x03, 0xFFFFFFFF)
+            time.sleep(0.002)
+            self.set_transceive_mode()
+            time.sleep(0.002)
+            self.send_data([0x26], valid_bits=0x07)
+            time.sleep(0.005)
+            rx_status = self.read_reg(0x13)
+            rx_len = rx_status & 0x1FF
+            if rx_len < 2 or rx_len == 511:
+                return None
+
+        atqa = self.read_data(2)
+        if atqa[0] == 0xFF or atqa[0] == 0x00:
+            return None
+
+        # Anti-collision Level 1
+        self.write_reg(0x03, 0xFFFFFFFF)
+        self.set_transceive_mode()
+        time.sleep(0.002)
+
+        self.send_data([0x93, 0x20])
+        time.sleep(0.010)
+
+        rx_status = self.read_reg(0x13)
+        rx_len = rx_status & 0x1FF
+        if rx_len < 5 or rx_len > 64:
+            return None
+
+        uid_buf = self.read_data(5)
+        uid = uid_buf[:4]
+        bcc = uid[0] ^ uid[1] ^ uid[2] ^ uid[3]
+        if bcc != uid_buf[4]:
+            return None
+
+        # SELECT
+        self.write_reg(0x03, 0xFFFFFFFF)
+        self.set_transceive_mode()
+        time.sleep(0.002)
+
+        # Enable CRC for SELECT
+        self.write_reg_or(0x19, 0x01)
+        self.write_reg_or(0x12, 0x01)
+
+        self.send_data([0x93, 0x70, uid[0], uid[1], uid[2], uid[3], bcc])
+        time.sleep(0.010)
+
+        rx_status = self.read_reg(0x13)
+        rx_len = rx_status & 0x1FF
+        if rx_len < 1:
+            return None
+
+        sak_buf = self.read_data(min(rx_len, 3))
+        sak = sak_buf[0]
+
+        return bytes(uid), sak
+
+    # -- MIFARE Classic --
+
+    def mfc_authenticate(self, block: int, key: bytes, uid: bytes) -> bool:
+        """MIFARE Classic authentication via PN5180 MFC_AUTHENTICATE (0x0C).
+
+        The PN5180 handles Crypto1 internally. After success, bit 6 of
+        SYSTEM_CONFIG is set (MFC_CRYPTO1_ON) and all subsequent RF
+        communication is encrypted/decrypted by the hardware.
+
+        Args:
+            block: Block number to authenticate
+            key: 6-byte MIFARE Key A
+            uid: 4-byte tag UID
+        Returns:
+            True if authentication succeeded
+        """
+        # Wait for BUSY LOW before starting
+        deadline = time.monotonic() + 0.100
+        while self._lines.get_value(BUSY_PIN) == gpiod.line.Value.ACTIVE:
+            if time.monotonic() > deadline:
+                return False
+            time.sleep(0.001)
+
+        # MFC_AUTHENTICATE: [0x0C][key 6B][keyType][blockNo][uid 4B] = 13 bytes
+        cmd = [0x0C] + list(key) + [0x60, block] + list(uid[:4])
+        self._cs_low()
+        self._spi.xfer2(cmd)
+        self._cs_high()
+
+        # Wait for BUSY HIGH then LOW (auth can take up to 1s)
+        self._wait_busy(timeout_s=1.0)
+
+        # Read 1-byte response: 0x00 = success
+        self._cs_low()
+        response = self._spi.xfer2([0xFF])
+        self._cs_high()
+
+        return response[0] == 0x00
+
+    def mfc_read_block(self, block: int) -> bytes | None:
+        """Read a 16-byte MIFARE Classic block (must be authenticated first).
+
+        Returns 16 bytes of block data, or None on failure.
+        """
+        # Clear IRQs
+        self.write_reg(0x03, 0xFFFFFFFF)
+
+        # Set transceive mode (Crypto1 stays active from MFC_AUTHENTICATE)
+        self.set_transceive_mode()
+        time.sleep(0.001)
+
+        # Enable TX and RX CRC for encrypted read
+        self.write_reg_or(0x19, 0x01)
+        self.write_reg_or(0x12, 0x01)
+
+        # Send MIFARE READ command: 0x30 + block number
+        self.send_data([0x30, block])
+        time.sleep(0.010)
+
+        # Check RX status
+        rx_status = self.read_reg(0x13)
+        rx_len = rx_status & 0x1FF
+        if rx_len != 16:
+            return None
+
+        return self.read_data(16)
+
+    def ntag_read_pages(self, start_page: int, num_pages: int) -> bytes | None:
+        """Read NTAG pages (4 bytes each). No authentication required.
+
+        Uses NTAG READ command (0x30) which returns 4 pages (16 bytes) at a time.
+        CRC must be disabled for NTAG reads.
+        """
+        # Disable CRC for NTAG
+        self.write_reg_and(0x19, 0xFFFFFFFE)  # TX CRC off
+        self.write_reg_and(0x12, 0xFFFFFFFE)  # RX CRC off
+
+        result = bytearray()
+        pages_read = 0
+        while pages_read < num_pages:
+            self.write_reg(0x03, 0xFFFFFFFF)  # Clear IRQs
+            self.set_transceive_mode()
+            time.sleep(0.001)
+
+            # READ command: 0x30 + page number → returns 16 bytes (4 pages)
+            self.send_data([0x30, start_page + pages_read])
+            time.sleep(0.005)
+
+            rx_status = self.read_reg(0x13)
+            rx_len = rx_status & 0x1FF
+            if rx_len < 16:
+                return None
+
+            data = self.read_data(16)
+            # Copy only the pages we need
+            pages_to_copy = min(4, num_pages - pages_read)
+            result.extend(data[: pages_to_copy * 4])
+            pages_read += 4  # Always advances by 4 (READ returns 4 pages)
+
+        return bytes(result)
+
+    def reactivate_card(self) -> tuple[bytes, int] | None:
+        """RF cycle and full re-select of the card. Returns (uid, sak) or None."""
+        self.rf_off()
+        time.sleep(0.010)
+
+        self.write_reg(0x03, 0xFFFFFFFF)  # Clear IRQs
+        self.load_rf_config(0x00, 0x80)  # ISO 14443A
+        time.sleep(0.005)
+
+        self.rf_on()
+        time.sleep(0.020)
+
+        return self.activate_type_a()
+
+    def read_bambu_tag(self, uid: bytes) -> dict[int, bytes] | None:
+        """Read Bambu tag data blocks using HKDF-derived keys.
+
+        Args:
+            uid: 4-byte tag UID (from activate_type_a)
+        Returns:
+            Dict mapping block number -> 16 bytes of data, or None on failure
+        """
+        # Derive per-sector keys from UID
+        keys = hkdf_derive_keys(uid)
+
+        # Clear Crypto1 state and IRQs
+        self.write_reg_and(0x00, 0xFFFFFFBF)  # Clear MFC_CRYPTO1_ON (bit 6)
+        self.write_reg(0x03, 0xFFFFFFFF)
+
+        # Reactivate card (may have timed out)
+        result = self.reactivate_card()
+        if result is None:
+            print("    Failed to reactivate card")
+            return None
+
+        uid_check, _ = result
+        if uid_check != uid:
+            print(f"    UID mismatch after reactivation: {uid_check.hex()} != {uid.hex()}")
+            return None
+
+        # Read blocks with per-sector authentication
+        blocks = {}
+        current_sector = -1
+
+        for block in BAMBU_BLOCKS:
+            sector = block // 4
+
+            # Authenticate when entering a new sector
+            if sector != current_sector:
+                key = get_sector_key(keys, block)
+                if not self.mfc_authenticate(block, key, uid):
+                    print(f"    Auth failed for block {block} (sector {sector})")
+                    return None
+                current_sector = sector
+
+            # Read the block
+            data = self.mfc_read_block(block)
+            if data is None:
+                print(f"    Read failed for block {block}")
+                return None
+            blocks[block] = data
+
+        return blocks
+
+    def ntag_write_page(self, page: int, data: bytes) -> bool:
+        """Write 4 bytes to a single NTAG page.
+
+        NTAG WRITE command: 0xA2 + page_number + 4 bytes data.
+        CRC disabled (same as reads). Returns True on ACK (0x0A).
+        """
+        if len(data) != 4:
+            return False
+
+        # Disable CRC
+        self.write_reg_and(0x19, 0xFFFFFFFE)  # TX CRC off
+        self.write_reg_and(0x12, 0xFFFFFFFE)  # RX CRC off
+
+        # Clear IRQs and set transceive mode
+        self.write_reg(0x03, 0xFFFFFFFF)
+        self.set_transceive_mode()
+        time.sleep(0.001)
+
+        # WRITE command: 0xA2 + page + 4 bytes
+        self.send_data([0xA2, page] + list(data))
+        time.sleep(0.005)
+
+        # Check for ACK: NTAG ACK is 4-bit 0x0A
+        rx_status = self.read_reg(0x13)
+        rx_len = rx_status & 0x1FF
+        if rx_len < 1:
+            return False
+
+        ack = self.read_data(1)
+        return ack[0] == 0x0A
+
+    def ntag_write_pages(self, start_page: int, data: bytes) -> bool:
+        """Write data to consecutive NTAG pages starting at start_page.
+
+        Pads last chunk to 4 bytes. Verifies by reading back.
+        Returns True if write + verify succeeded.
+        """
+        # Pad to 4-byte boundary
+        padded = bytearray(data)
+        while len(padded) % 4 != 0:
+            padded.append(0x00)
+
+        # Write page by page
+        for i in range(0, len(padded), 4):
+            page = start_page + (i // 4)
+            chunk = bytes(padded[i : i + 4])
+            if not self.ntag_write_page(page, chunk):
+                return False
+            time.sleep(0.002)
+
+        # Reactivate card for verification read
+        result = self.reactivate_card()
+        if result is None:
+            return False
+
+        # Read back and verify
+        num_pages = len(padded) // 4
+        readback = self.ntag_read_pages(start_page, num_pages)
+        if readback is None:
+            return False
+
+        return readback[: len(data)] == data
+
+    def read_ntag(self, uid: bytes) -> bytes | None:
+        """Read NTAG pages 4-20 (NDEF data area, 68 bytes). No auth needed.
+
+        Used for SpoolEase / OpenPrintTag community tags.
+        """
+        # Reactivate card
+        result = self.reactivate_card()
+        if result is None:
+            print("    Failed to reactivate card")
+            return None
 
-# Show driver debug output during diagnostics
-logging.basicConfig(level=logging.DEBUG, format="  %(message)s")
+        return self.ntag_read_pages(start_page=4, num_pages=17)
 
 
 def _print_hex_dump(data: bytes, label: str, bytes_per_line: int = 16):
@@ -56,7 +583,7 @@ def main():
         else:
             print("\nCheck:")
             print("  - Correct GPIO chip is available (/dev/gpiochip0 or /dev/gpiochip4)")
-            print("  - SPI device is available")
+            print(f"  - SPI device is available (SPI_BUS={SPI_BUS}, SPI_DEVICE={SPI_DEVICE})")
             print("  - GPIO and SPI permissions are correct")
             # Only print full traceback for unexpected errors
             import traceback

spoolbuddy/scripts/scale_diag.py

@@ -1,23 +1,152 @@
 #!/usr/bin/env python3
-"""NAU7802 Scale Diagnostic.
+"""NAU7802 Scale Diagnostic - ported from SpoolBuddy Rust firmware.
 
-Standalone diagnostic script — the NAU7802 driver lives in
-spoolbuddy/daemon/nau7802.py and is imported from there.
+I2C address: 0x2A
+Bus: /dev/i2c-1 (GPIO2/GPIO3 on RPi)
 """
 
-import logging
+import os
+import struct
 import sys
 import time
-from pathlib import Path
 
 import smbus2
 
-# Add daemon package to sys.path so we can import the driver
-sys.path.insert(0, str(Path(__file__).resolve().parent.parent))
-from daemon.nau7802 import I2C_BUS, NAU7802, NAU7802_ADDR
 
-# Show driver debug output (init steps, etc.) during diagnostics
-logging.basicConfig(level=logging.DEBUG, format="  %(message)s")
+def _env_int(name: str, default: int) -> int:
+    value = os.environ.get(name)
+    if value is None or value == "":
+        return default
+    try:
+        return int(value)
+    except ValueError:
+        return default
+
+
+I2C_BUS = _env_int("SPOOLBUDDY_I2C_BUS", 1)
+NAU7802_ADDR = 0x2A
+
+# Register addresses
+REG_PU_CTRL = 0x00
+REG_CTRL1 = 0x01
+REG_CTRL2 = 0x02
+REG_ADCO_B2 = 0x12  # ADC output MSB
+REG_ADCO_B1 = 0x13
+REG_ADCO_B0 = 0x14  # ADC output LSB
+REG_ADC = 0x15
+REG_PGA = 0x1B
+REG_PWR_CTRL = 0x1C
+REG_REVISION = 0x1F
+
+# PU_CTRL bits
+PU_RR = 0x01  # Register reset
+PU_PUD = 0x02  # Power up digital
+PU_PUA = 0x04  # Power up analog
+PU_PUR = 0x08  # Power up ready (read-only)
+PU_CS = 0x10  # Cycle start
+PU_CR = 0x20  # Cycle ready (read-only)
+PU_OSCS = 0x40  # Oscillator select
+PU_AVDDS = 0x80  # AVDD source select
+
+
+class NAU7802:
+    def __init__(self, bus=I2C_BUS, addr=NAU7802_ADDR):
+        self._bus_num = bus
+        self._bus = smbus2.SMBus(bus)
+        self._addr = addr
+
+    def close(self):
+        self._bus.close()
+
+    def read_reg(self, reg: int) -> int:
+        return self._bus.read_byte_data(self._addr, reg)
+
+    def write_reg(self, reg: int, val: int):
+        self._bus.write_byte_data(self._addr, reg, val & 0xFF)
+
+    def _update_bits(self, reg: int, mask: int, value: int):
+        cur = self.read_reg(reg)
+        self.write_reg(reg, (cur & ~mask) | (value & mask))
+
+    def _set_bit(self, reg: int, bit: int, enabled: bool):
+        mask = 1 << bit
+        self._update_bits(reg, mask, mask if enabled else 0)
+
+    def _set_field(self, reg: int, shift: int, width: int, value: int):
+        mask = ((1 << width) - 1) << shift
+        self._update_bits(reg, mask, value << shift)
+
+    def init(self):
+        """Initialize NAU7802 using the Adafruit library startup sequence."""
+
+        # Reset
+        self._set_bit(REG_PU_CTRL, 0, True)  # RR=1
+        time.sleep(0.010)
+        self._set_bit(REG_PU_CTRL, 0, False)  # RR=0
+        self._set_bit(REG_PU_CTRL, 1, True)  # PUD=1
+        time.sleep(0.001)
+
+        # Enable digital + analog and allow analog section to settle.
+        self._set_bit(REG_PU_CTRL, 1, True)  # PUD=1
+        self._set_bit(REG_PU_CTRL, 2, True)  # PUA=1
+        time.sleep(0.600)
+
+        # Start conversion cycle (PU_CS bit 4) after power-up.
+        self._set_bit(REG_PU_CTRL, 4, True)
+
+        # Wait for power-up ready (PU_PUR bit 3)
+        for _ in range(100):
+            status = self.read_reg(REG_PU_CTRL)
+            if status & PU_PUR:
+                print("  Power-up ready")
+                break
+            time.sleep(0.001)
+        else:
+            raise TimeoutError("NAU7802 power-up timeout")
+
+        # Check revision register low nibble (Adafruit expects 0xF).
+        revision = self.read_reg(REG_REVISION)
+        print(f"  Revision: 0x{revision:02X}")
+        if (revision & 0x0F) != 0x0F:
+            raise RuntimeError(f"Unexpected NAU7802 revision register: 0x{revision:02X}")
+
+        # Internal LDO enable is PU_CTRL.AVDDS (bit 7); set LDO voltage to 3.0V.
+        self._set_bit(REG_PU_CTRL, 7, True)  # AVDDS=1 (internal LDO)
+        self._set_field(REG_CTRL1, shift=3, width=3, value=0b101)  # VLDO=3.0V
+        print("  LDO: 3.0V (internal)")
+
+        # Gain: 128x (bits 2:0 of CTRL1 = 0b111)
+        self._set_field(REG_CTRL1, shift=0, width=3, value=0b111)
+        print("  Gain: 128x")
+
+        # Sample rate: 10 SPS (CTRL2 bits 6:4 = 0b000)
+        self._set_field(REG_CTRL2, shift=4, width=3, value=0b000)
+        print("  Sample rate: 10 SPS")
+
+        # Adafruit tuning: disable ADC chopper clock (ADC bits 5:4 = 0b11)
+        self._set_field(REG_ADC, shift=4, width=2, value=0b11)
+
+        # Adafruit tuning: use low ESR caps (PGA bit 6 = 0)
+        self._set_bit(REG_PGA, 6, False)
+
+        # Start conversion cycle
+        self._set_bit(REG_PU_CTRL, 4, True)
+        print("  Conversion started")
+
+    def data_ready(self) -> bool:
+        return bool(self.read_reg(REG_PU_CTRL) & PU_CR)
+
+    def read_raw(self) -> int:
+        """Read 24-bit signed ADC value."""
+        b2 = self.read_reg(REG_ADCO_B2)
+        b1 = self.read_reg(REG_ADCO_B1)
+        b0 = self.read_reg(REG_ADCO_B0)
+        raw = (b2 << 16) | (b1 << 8) | b0
+        # Sign extend 24-bit to 32-bit
+        if raw & 0x800000:
+            raw |= 0xFF000000
+            raw = struct.unpack("i", struct.pack("I", raw))[0]
+        return raw
 
 
 def main():
@@ -62,7 +191,6 @@ def main():
     try:
         print("[1] Initializing...")
         scale.init()
-        print("  Initialized OK")
 
         print("[2] Waiting for first reading...")
         for _ in range(200):