I2C串列通訊實作Part4 – RFID

電路圖

 

 

 

 

程式列表

• epy_pn532.py

"""  epy_pn532.py    ePy   PN532  ------------  3V3   VCC  P19   SCL  P20   SDA  GND   GND """   from machine import KEY  #獲取按鍵KEY庫 from pn532api import PN532   if __name__== "__main__":   key_c = KEY(KEY.KEYC)    #創建按鍵C   nfc = PN532()     # setup the device   nfc.setup()     # keep reading until a value is returned   while True:     read = nfc.read()     #print(read)     print("".join("\\x%02x" % i for i in read))     if key_c.value() == 0:      #如果按鍵C被按下       break   key_c.deinit()

 

• pn532api.py

""" # pn532api.py contains a set of core functions  Reference: https://github.com/hoanhan101/pn532 """   from micropython import const from machine import I2C, PIN import pn532register import utime   # rest time in second betweet each read/write transaction REST_INTERVAL = 500   # maximum block size for each read transaction BLOCK_SIZE = 20   class PN532(object):   def __init__(self):     # i2c device address     self.address = pn532register.PN532_DEFAULT_ADDRESS       # smbus object     self.bus = I2C(1,100000)    #創建頻率為100kHz的I2C外設,選擇要使用的外設I2C 1     def setup(self):     """setup the device"""     self.sam_config()     def read(self):     """return a raw reading value as an array of bytes"""     self.in_list_passive_target()       while True:       read = self.read_addr(BLOCK_SIZE)       # check the first 3 bytes to see if a card is detected or not       if read[:3] != [0x00, 0x80, 0x80]:         # TODO - the first 9 bytes are configs bytes so we're not really         # interested in getting these at the moment, though they could         # be used for validation in the future         return read[9:]     def sam_config(self):     """send SAMConfiguration command"""     self.write_addr(       construct_frame([pn532register._COMMAND_SAMCONFIGURATION, 0x01, 0x01, 0x00])     )     self.read_addr(BLOCK_SIZE)     def in_list_passive_target(self):     """send InListPassiveTarget command"""     self.write_addr(       construct_frame([pn532register._COMMAND_INLISTPASSIVETARGET, 0x01, 0x00])     )     self.read_addr(BLOCK_SIZE)     def write_addr(self, data):     """write to its own address with given block data"""     utime.sleep_ms(REST_INTERVAL)       self.bus.write(1,self.address,data,len(data),1)     def read_addr(self, length):     """read from its own address a given-length of block data"""     utime.sleep_ms(REST_INTERVAL)       buf = bytearray(length)     self.bus.read(1,self.address,buf,length,1)     return buf   def construct_frame(data):   """construct frame for communicating between host controller and pn532"""   # begin with 6-bytes frame structure   buf = [0x00, 0x00, 0x00, 0x00, 0x00, 0x00]   buf[0] = pn532register._PREAMBLE   buf[1] = pn532register._STARTCODE1   buf[2] = pn532register._STARTCODE2   buf[3] = len(data) + 1       # number of bytes in data and frame identifier field   buf[4] = (~buf[3] & 0xFF) + 0x01 # packet length checksum   buf[5] = pn532register._HOSTTOPN532     tmp_sum = pn532register._HOSTTOPN532   for b in data:     tmp_sum += b     buf.append(b)     buf.append((~tmp_sum & 0xFF) + 0x01) # data checksum   buf.append(pn532register._POSTAMBLE)     return buf

 

• pn532register.py

# -*- coding: utf-8 -*- # # pn532register.py contains a set of registers addresses mapping #   PN532_DEFAULT_ADDRESS = 0x24   _PREAMBLE   = 0x00 _STARTCODE1 = 0x00 _STARTCODE2 = 0xFF _POSTAMBLE  = 0x00   # frame identifier _HOSTTOPN532 = 0xD4   _COMMAND_SAMCONFIGURATION = 0x14 _COMMAND_INLISTPASSIVETARGET = 0x4A

 執行結果