MicroPython_PN532/adafruit_pn532/spi.py

# Adafruit PN532 NFC/RFID control library.
# Author: Tony DiCola
#
# The MIT License (MIT)
#
# Copyright (c) 2015-2018 Adafruit Industries
#
# Permission is hereby granted, free of charge, to any person obtaining a copy
# of this software and associated documentation files (the "Software"), to deal
# in the Software without restriction, including without limitation the rights
# to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
# copies of the Software, and to permit persons to whom the Software is
# furnished to do so, subject to the following conditions:
#
# The above copyright notice and this permission notice shall be included in
# all copies or substantial portions of the Software.
#
# THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
# IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
# FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
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# THE SOFTWARE.
"""
``adafruit_pn532.spi``
====================================================

This module will let you communicate with a PN532 RFID/NFC shield or breakout
using SPI.

* Author(s): Original Raspberry Pi code by Tony DiCola, CircuitPython by ladyada,
             refactor by Carter Nelson

"""

__version__ = "0.0.0-auto.0"
__repo__ = "https://github.com/adafruit/Adafruit_CircuitPython_PN532.git"

import time
from adafruit_pn532.adafruit_pn532 import PN532 
import adafruit_bus_device.spi_device as spi_device

from micropython import const

_SPI_STATREAD                  = const(0x02)
_SPI_DATAWRITE                 = const(0x01)
_SPI_DATAREAD                  = const(0x03)
_SPI_READY                     = const(0x01)

def reverse_bit(num):
    """Turn an LSB byte to an MSB byte, and vice versa. Used for SPI as
    it is LSB for the PN532, but 99% of SPI implementations are MSB only!"""
    result = 0
    for _ in range(8):
        result <<= 1
        result += (num & 1)
        num >>= 1
    return result

class PN532_SPI(PN532):
    """Driver for the PN532 connected over SPI. Pass in a hardware or bitbang
    SPI device & chip select digitalInOut pin. Optional IRQ pin (not used),
    reset pin and debugging output."""
    def __init__(self, spi, cs_pin, *, irq=None, reset=None, debug=False):
        """Create an instance of the PN532 class using SPI"""
        self.debug = debug
        self._irq = irq
        self._spi = spi_device.SPIDevice(spi, cs_pin)
        super().__init__(debug=debug, reset=reset)

    def _wakeup(self):
        """Send any special commands/data to wake up PN532"""
        with self._spi as spi:
            time.sleep(1)
            spi.write(bytearray([0x00])) #pylint: disable=no-member
            time.sleep(1)

    def _wait_ready(self, timeout=1):
        """Poll PN532 if status byte is ready, up to `timeout` seconds"""
        status = bytearray([reverse_bit(_SPI_STATREAD), 0])

        timestamp = time.monotonic()
        while (time.monotonic() - timestamp) < timeout:
            with self._spi as spi:
                time.sleep(0.02)   # required
                spi.write_readinto(status, status) #pylint: disable=no-member
            if reverse_bit(status[1]) == 0x01:  # LSB data is read in MSB
                return True      # Not busy anymore!
            else:
                time.sleep(0.01)  # pause a bit till we ask again
        # We timed out!
        return False

    def _read_data(self, count):
        """Read a specified count of bytes from the PN532."""
        # Build a read request frame.
        frame = bytearray(count+1)
        # Add the SPI data read signal byte, but LSB'ify it
        frame[0] = reverse_bit(_SPI_DATAREAD)

        with self._spi as spi:
            time.sleep(0.02)   # required
            spi.write_readinto(frame, frame) #pylint: disable=no-member
        for i, val in enumerate(frame):
            frame[i] = reverse_bit(val) # turn LSB data to MSB
        if self.debug:
            print("Reading: ", [hex(i) for i in frame[1:]])
        return frame[1:]

    def _write_data(self, framebytes):
        """Write a specified count of bytes to the PN532"""
        # start by making a frame with data write in front,
        # then rest of bytes, and LSBify it
        rev_frame = [reverse_bit(x) for x in bytes([_SPI_DATAWRITE]) + framebytes]
        if self.debug:
            print("Writing: ", [hex(i) for i in rev_frame])
        with self._spi as spi:
            time.sleep(0.02)   # required
            spi.write(bytes(rev_frame)) #pylint: disable=no-member