'''
Created on Dec 19, 2016

@author: klaehn
'''
import smbus

class PowerSensor(object):
    '''
    Power sensor wrapper
    '''
    def __init__(self, bus = 1, addr = 0x40):
        self.__bus = smbus.SMBus(bus)
        self.__addr = addr

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

    def shunt_voltage_mv(self):
        ''' Read the voltage at the shunt resistor [mV] '''
        data = self.__bus.read_i2c_block_data(self.__addr, 0x01)
        voltage = data[0] * 256 + data[1]
        return voltage * 0.01

    def current_ma(self):
        ''' Read the current [mA] '''
        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):
        ''' Read the power [mW] '''
        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