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#!/usr/bin/python
from Adafruit_I2C import Adafruit_I2C

class RA_ORP(object):

    def __init__(self, address = 0x4C, busnum = 1, calibration = ( 1480, 367, 0, 400 )):
        self.i2c = Adafruit_I2C(address=address)     
        self.address = address
	self.calibration = calibration
	self.queue = []
    	self.lastRaw = 0
    	self.overCnt = 0
    	self.maxChange = 300
	self.maxOverCnt = 20
	self.queueLength = 20
	self.debug = 0


    def readRaw(self):
	return self.i2c.reverseByteOrder(self.i2c.readU16(0x00))

    def readSingle(self):
	return self.convert(self.readRaw())

    def read(self):
	value = self.readRaw()
	if self.debug: print "Raw value read:",value
        if self.lastRaw == 0 or abs(value - self.lastRaw) < self.maxChange:
                self.queue.append(value)
                self.lastRaw = value
                self.overCnt = 0
        else:
                self.overCnt += 1
                if self.overCnt > self.maxOverCnt:
                        self.overCnt = 0
                        self.queue.append(value)
                        self.lastRaw = value

        if len(self.queue) > self.queueLength:
                self.queue.pop(0)

	return self.convert(self.mean())

    def convert(self,x):
    	return (x - self.calibration[0]) * (self.calibration[3] - self.calibration[2]) // (self.calibration[1] - self.calibration[0]) + self.calibration[2]

    def mean(self):
    	n = len(self.queue)
    	if n < 1:
        	raise ValueError('mean requires at least one data point')
    	return sum(self.queue)/n