Python 논 블로킹 pn532 태그 읽기

Question

내 프로젝트에 Adafruit PN532 nfc https://www.adafruit.com/product/364 브레이크 아웃 카드를 사용할 계획입니다.

이 코드 샘플 에서처럼 루프를 피하기 위해 비 차단 코드를 파이썬 (인터럽트를 사용하여?)에 작성하는 방법이 있습니까?

https://github.com/adafruit/Adafruit_Python_PN532/blob/master/examples/readmifare.py

Answer 1

(내 의견에 대하여 ..) asyncio 조금 가벼운 무게이지만, threading 또한 시스템을 호출하는 이벤트를 가지고 있으며, 현재 더 나은 (스레딩 asyncio보다 더 오래되고와있다 문서화 조금 조금 덜 추상적입니다.) 내가 이해할 때, 당신은 다른 작업을하면서 블로킹 리소스를 읽을 수 있기를 원합니다. 이 경우 텍스트 파일을 표준 출력으로 천천히 인쇄하면서 카드를 읽을 때까지 대기 할 스레드를 생성합니다. 이것은 그런 식으로하는 방법의 예일뿐입니다. 비슷한 결과를 얻는 방법은 여러 가지가 있습니다.

import binascii 
import time 
import threading 
from collections import deque #use as a fifo queue 

queue = deque() #queue to pass information from thread to main process 
queue_lock = threading.Lock() #prevent possible issues from 
txt_file = '50_shades_of_grey.txt' #don't ask ;) 
running = True 

def nfc_reader(): 
    #copied from adafruit example 
    import Adafruit_PN532 as PN532 
    CS = 18 
    MOSI = 23 
    MISO = 24 
    SCLK = 25 

    pn532 = PN532.PN532(cs=CS, sclk=SCLK, mosi=MOSI, miso=MISO) 
    pn532.begin() 
    ic, ver, rev, support = pn532.get_firmware_version() 
    print(f'Found PN532 with firmware version: {ver}.{rev}') 
    pn532.SAM_configuration() 

    # Main loop to detect cards and read a block. 
    print('Waiting for MiFare card...') 
    while True: 
     if not running: #cheap way to kill a thread nicely (cheap ain't pretty) 
      return 
     #don't bother specifying a timeout, they forgot to support it in the library 
     uid = pn532.read_passive_target() 
     # Try again if no card is available. 
     if uid is None: 
      continue 
     print('Found card with UID: 0x{0}'.format(binascii.hexlify(uid))) 
     # Authenticate block 4 for reading with default key (0xFFFFFFFFFFFF). 
     if not pn532.mifare_classic_authenticate_block(uid, 4, PN532.MIFARE_CMD_AUTH_B, 
                 [0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF]): 
      print('Failed to authenticate block 4!') 
      continue 
     # Read block 4 data. 
     data = pn532.mifare_classic_read_block(4) 
     if data is None: 
      print('Failed to read block 4!') 
      continue 
     # make sure our queue is free 
     with queue_lock: 
      # replaced print with deque.append 
      queue.append(f'Read block 4: 0x{binascii.hexlify(data[:4])}') 
     #optionally emit some sort of signal that data is ready. In our case the main loop will chech periodically on it's own 

# Main program 
nfc_thread = threading.Thread(target=nfc_reader) 
nfc_thread.start() 

with open(txt_file, 'r') as f: 
    while True: #also cheap, but easy 
     if queue: #bool(deque) works like bool(list) 
      with queue_lock: 
       print("we found a card!") 
       print(queue.popleft()) 
       continue 
     try: 
      print(next(f)) #otherwise go back to more interesting matters 
     except StopIteration: 
      running = False 
      nfc_thread.join() 
      break 
     time.sleep(.9) #notice loop time will be less than timeout on nfc read. 
         # you could put the printing of the *book* into another thread 
         # and use events to immediately call your return from your 
         # nfc reader

Answer 2

여기에 당신이 이벤트 루프와 이벤트 기반의 코딩 스타일을 볼 필요가

import binascii 
import time 
import threading 
from collections import deque #use as a fifo queue 
import RPi.GPIO as GPIO 
import Adafruit_PN532 as PN532 

queue = deque() #queue to pass information from thread to main process 
queue_lock = threading.Lock() #prevent possible issues from 
running = True 

def nfc_reader(): 
    CS = 18 
    MOSI = 23 
    MISO = 24 
    SCLK = 25 

    pn532 = PN532.PN532(cs=CS, sclk=SCLK, mosi=MOSI, miso=MISO) 
    pn532.begin() 
    ic, ver, rev, support = pn532.get_firmware_version() 
    print('Found PN532 with firmware version: {0}.{1}'.format(ver, rev)) 
    pn532.SAM_configuration() 

    while True: 
     if not running: #cheap way to kill a thread nicely (cheap ain't pretty) 
      return 

     uid = pn532.read_passive_target() 
     if uid is None: 
      continue 
     #print('card read') 
     message = 'Read card\n{0}'.format(binascii.hexlify(uid)) 

     # make sure our queue is free 
     with queue_lock: 
      # replaced print with deque.append 
      queue.append(message) 
      time.sleep(1) 
     #optionally emit some sort of signal that data is ready. In our case the main loop will chech periodically on it's own 

# Main program 
nfc_thread = threading.Thread(target=nfc_reader) 
nfc_thread.start() 


while True: #also cheap, but easy 
    if queue: #bool(deque) works like bool(list) 
     with queue_lock: 
      print("we found a card!") 
      print(queue.popleft()) 
      continue 
    time.sleep(.9) #notice loop time will be less than timeout on nfc read. 
        # you could put the printing of the *book* into another thread 
        # and use events to immediately call your return from your 
        # nfc reader