MicroPython_PN532/adafruit_pn532/spi.py
2020-08-23 11:01:52 -05:00

123 lines
4.7 KiB
Python

# 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
# AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
# LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
# OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
# 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
import adafruit_bus_device.spi_device as spi_device
from micropython import const
from adafruit_pn532.adafruit_pn532 import PN532
_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_cmd = bytearray([reverse_bit(_SPI_STATREAD), 0x00])
status_response = bytearray([0x00, 0x00])
timestamp = time.monotonic()
with self._spi as spi:
while (time.monotonic() - timestamp) < timeout:
time.sleep(0.02) # required
spi.write_readinto(
status_cmd, status_response
) # pylint: disable=no-member
if reverse_bit(status_response[1]) == 0x01: # LSB data is read in MSB
return True # Not busy anymore!
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