MicroPython_PN532/adafruit_pn532/uart.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.uart``
====================================================

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

* 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, BusyError


class PN532_UART(PN532):
    """Driver for the PN532 connected over Serial UART"""

    def __init__(self, uart, *, reset=None, debug=False):
        """Create an instance of the PN532 class using Serial connection.
        Optional reset pin and debugging output.
        """
        self.debug = debug
        self._uart = uart
        super().__init__(debug=debug, reset=reset)

    def _wakeup(self):
        """Send any special commands/data to wake up PN532"""
        if self._reset_pin:
            self._reset_pin.value = True
            time.sleep(0.01)
        self.low_power = False
        self._uart.write(
            b"\x55\x55\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00"
        )  # wake up!
        self.SAM_configuration()

    def _wait_ready(self, timeout=1):
        """Wait `timeout` seconds"""
        timestamp = time.monotonic()
        while (time.monotonic() - timestamp) < timeout:
            if self._uart.in_waiting > 0:
                return True  # No Longer Busy
            time.sleep(0.01)  # lets ask again soon!
        # Timed out!
        return False

    def _read_data(self, count):
        """Read a specified count of bytes from the PN532."""
        frame = self._uart.read(count)
        if not frame:
            raise BusyError("No data read from PN532")
        if self.debug:
            print("Reading: ", [hex(i) for i in frame])
        return frame

    def _write_data(self, framebytes):
        """Write a specified count of bytes to the PN532"""
        self._uart.reset_input_buffer()
        self._uart.write(framebytes)