import smbus

class power_sensor:
	def __init__(self, bus = 1, addr = 0x40):
		self.bus = smbus.SMBus(bus)
		self.addr = addr

		bytes = [(0x1000 >> 8) & 0xFF, 0x1000 & 0xFF]
		self.bus.write_i2c_block_data(self.addr, 0x05, bytes)
		config = 0x2000 | 0x1800 | 0x0400 | 0x0018 | 0x0007
		bytes = [(config >> 8) & 0xFF, config & 0xFF]
		self.bus.write_i2c_block_data(self.addr, 0x00, bytes)

	def shunt_voltage_mv(self):
		data = self.bus.read_i2c_block_data(self.addr, 0x01)
		voltage = data[0] * 256 + data[1]
		return voltage * 0.01

	def current_ma(self):
		data = self.bus.read_i2c_block_data(self.addr, 0x04)
		if(data[0] >> 7 == 1):
			current = data[0] * 256 + data[1]
			if(current & (1 << 15)):
				current = current - (1 << 16)
		else:
			current = (data[0] << 8) | (data[1])
		return current / 10

	def power_mw(self):
		data = self.bus.read_i2c_block_data(self.addr, 0x03)
		if(data[0] >> 7 == 1):
			power = data[0] * 256 + data[1]
			if(power & (1 << 15)):
				power = power - (1 << 16)
		else:
			power = (data[0] << 8) | (data[1])
		return power / 2