[英]Python Wiegand 34bits - ignore last 2 bits
我正在嘗試使用 python 從 QR 閱讀器讀取代碼。使用了此處的 pigpio 示例http://abyz.me.uk/rpi/pigpio/examples.html#Python_wiegand_py
當我掃描 QR 時,它返回bits=34 value=12835750879
這太長了,代碼應該只有 10 位。 QR 發送 34 位,安裝它的人說我需要忽略最后 2 位,只取 0-31,問題是我不太了解代碼,我來自 PHP,這無關緊要帶位和 memory。
這是處理讀取的代碼部分,我認為在_cb
function 的某處。
有人可以幫助我更好地理解代碼,以便我可以 go 進入正確的方向嗎?
def __init__(self, pi, gpio_0, gpio_1, callback, bit_timeout=5):
"""
Instantiate with the pi, gpio for 0 (green wire), the gpio for 1
(white wire), the callback function, and the bit timeout in
milliseconds which indicates the end of a code.
The callback is passed the code length in bits and the value.
"""
self.pi = pi
self.gpio_0 = gpio_0
self.gpio_1 = gpio_1
self.callback = callback
self.bit_timeout = bit_timeout
self.in_code = False
self.pi.set_mode(gpio_0, pigpio.INPUT)
self.pi.set_mode(gpio_1, pigpio.INPUT)
self.pi.set_pull_up_down(gpio_0, pigpio.PUD_UP)
self.pi.set_pull_up_down(gpio_1, pigpio.PUD_UP)
self.cb_0 = self.pi.callback(gpio_0, pigpio.FALLING_EDGE, self._cb)
self.cb_1 = self.pi.callback(gpio_1, pigpio.FALLING_EDGE, self._cb)
def _cb(self, gpio, level, tick):
"""
Accumulate bits until both gpios 0 and 1 timeout.
"""
if level < pigpio.TIMEOUT:
if self.in_code == False:
self.bits = 1
self.num = 0
self.in_code = True
self.code_timeout = 0
self.pi.set_watchdog(self.gpio_0, self.bit_timeout)
self.pi.set_watchdog(self.gpio_1, self.bit_timeout)
else:
self.bits += 1
self.num = self.num << 1
if gpio == self.gpio_0:
self.code_timeout = self.code_timeout & 2 # clear gpio 0 timeout
else:
self.code_timeout = self.code_timeout & 1 # clear gpio 1 timeout
self.num = self.num | 1
else:
if self.in_code:
if gpio == self.gpio_0:
self.code_timeout = self.code_timeout | 1 # timeout gpio 0
else:
self.code_timeout = self.code_timeout | 2 # timeout gpio 1
if self.code_timeout == 3: # both gpios timed out
self.pi.set_watchdog(self.gpio_0, 0)
self.pi.set_watchdog(self.gpio_1, 0)
self.in_code = False
self.callback(self.bits, self.num)
要刪除最后兩位,您可以使用bin()
將 integer self.num
轉換為二進制字符串,去掉兩個字符,然后轉換回 integer。
這是一個例子:
num = 2**34 - 1 # 17179869183
num_b = bin(num) # '0b1111111111111111111111111111111111'
num = int(num_b[:-2], base=2) # 4294967295
所以你想在代碼中的某個地方使用int(bin(self.num)[:-2], 2)
來檢索完整的二維碼。
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