busfahrer.py 1.81 KB
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from smbus import SMBus
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from libtuer import logger
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from threading import RLock

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class Pin:
	def __init__(self, addr, bit):
		assert 0 <= bit and bit < 8, "There are only 8 bits per byte"
		self.addr = addr
		self.bit  = bit
	
	def __str__(self):
		return "{0:x}.{1}".format(self.addr, self.bit)

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class I2C:
	'''This class manages the I²C bus.
	It is thread-safe.
	'''
	def __init__(self, bus):
		self._bus = SMBus(bus)
		self._bytes = {} # this maps bytes to the last written value
		self._active = False # for now, we are in initialization mode
		self._lock = RLock()
	
	def activate(self):
		'''This function activates the bus. Only now, stuff is sent to the HW.
		Call this after all relevant pings have default values.'''
		with self._lock:
			self._active = True
			for addr, byte in self._bytes.items():
				self.setPins(addr, byte)
	
	def setPins(self, addr, stateByte):
		'''Set all pins of the given address'''
		with self._lock:
			if self._active:
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				#logger.debug("I2C: Setting 0x{:x} to {:08b}".format(addr, stateByte))
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				self._bus.write_byte(addr, stateByte)
			self._bytes[addr] = stateByte
	
	def setPin(self, pin, state):
		'''Set the gien pin: An (address, bit) pair'''
		with self._lock:
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			byte = self._bytes.get(pin.addr, 0xFF) # default: all-1. That's also the HW default state, inherently.
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			# set the bit
			if state:
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				byte |= (1 << pin.bit)
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			else:
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				byte &= ~(1 << pin.bit)
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			# now we know what to set
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			self.setPins(pin.addr, byte)
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	def getPins(self, addr):
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		with self._lock:
			if not self._active:
				return None
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			return self._bus.read_byte(addr)
	
	def getPin(self, pin):
		# read the current value
		byte = self.getPins(pin.addr)
		if byte is None: return None
		# now we need to get the bit
		mask = (1 << pin.bit)
		return bool(byte & mask)
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# kate: space-indent off; tab-width 4; indent-width 4;