103 lines
3.7 KiB
Python
103 lines
3.7 KiB
Python
# SPDX-FileCopyrightText: 2015-2018 Tony DiCola for Adafruit Industries
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#
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# SPDX-License-Identifier: MIT
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"""
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``adafruit_pn532.spi``
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====================================================
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This module will let you communicate with a PN532 RFID/NFC shield or breakout
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using SPI.
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* Author(s): Original Raspberry Pi code by Tony DiCola, CircuitPython by ladyada,
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refactor by Carter Nelson
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"""
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__version__ = "0.0.0+auto.0"
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__repo__ = "https://github.com/adafruit/Adafruit_CircuitPython_PN532.git"
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import time
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from adafruit_bus_device import spi_device
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from micropython import const
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from adafruit_pn532.adafruit_pn532 import PN532
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_SPI_STATREAD = const(0x02)
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_SPI_DATAWRITE = const(0x01)
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_SPI_DATAREAD = const(0x03)
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_SPI_READY = const(0x01)
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def reverse_bit(num):
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"""Turn an LSB byte to an MSB byte, and vice versa. Used for SPI as
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it is LSB for the PN532, but 99% of SPI implementations are MSB only!"""
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result = 0
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for _ in range(8):
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result <<= 1
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result += num & 1
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num >>= 1
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return result
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class PN532_SPI(PN532):
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"""Driver for the PN532 connected over SPI. Pass in a hardware or bitbang
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SPI device & chip select digitalInOut pin. Optional IRQ pin (not used),
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reset pin and debugging output."""
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def __init__(self, spi, cs_pin, *, irq=None, reset=None, debug=False):
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"""Create an instance of the PN532 class using SPI"""
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self.debug = debug
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self._spi = spi_device.SPIDevice(spi, cs_pin)
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super().__init__(debug=debug, irq=irq, reset=reset)
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def _wakeup(self):
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"""Send any special commands/data to wake up PN532"""
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if self._reset_pin:
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self._reset_pin.value = True
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time.sleep(0.01)
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with self._spi as spi:
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spi.write(bytearray([0x00])) # pylint: disable=no-member
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time.sleep(0.01)
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self.low_power = False
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self.SAM_configuration() # Put the PN532 back in normal mode
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def _wait_ready(self, timeout=1):
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"""Poll PN532 if status byte is ready, up to `timeout` seconds"""
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status_cmd = bytearray([reverse_bit(_SPI_STATREAD), 0x00])
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status_response = bytearray([0x00, 0x00])
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timestamp = time.monotonic()
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with self._spi as spi:
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while (time.monotonic() - timestamp) < timeout:
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spi.write_readinto(
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status_cmd, status_response
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) # pylint: disable=no-member
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if reverse_bit(status_response[1]) == 0x01: # LSB data is read in MSB
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return True # Not busy anymore!
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time.sleep(0.01) # pause a bit till we ask again
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# We timed out!
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return False
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def _read_data(self, count):
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"""Read a specified count of bytes from the PN532."""
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# Build a read request frame.
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frame = bytearray(count + 1)
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# Add the SPI data read signal byte, but LSB'ify it
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frame[0] = reverse_bit(_SPI_DATAREAD)
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with self._spi as spi:
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spi.write_readinto(frame, frame) # pylint: disable=no-member
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for i, val in enumerate(frame):
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frame[i] = reverse_bit(val) # turn LSB data to MSB
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if self.debug:
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print("Reading: ", [hex(i) for i in frame[1:]])
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return frame[1:]
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def _write_data(self, framebytes):
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"""Write a specified count of bytes to the PN532"""
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# start by making a frame with data write in front,
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# then rest of bytes, and LSBify it
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rev_frame = [reverse_bit(x) for x in bytes([_SPI_DATAWRITE]) + framebytes]
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if self.debug:
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print("Writing: ", [hex(i) for i in rev_frame])
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with self._spi as spi:
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spi.write(bytes(rev_frame)) # pylint: disable=no-member
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