sgh_PCF8591P.py

#!/usr/bin/env python
'''
Created on 28 Nov 2012

@author: Jamie
'''

# Help with getting started with this device came from Mike 'Grumpy' Cook on the
# Raspberry Pi Forums (http://www.raspberrypi.org/phpBB3/viewtopic.php?f=32&t=15578)

# Mike's very interesting site can be found at: http://www.thebox.myzen.co.uk/Site/Welcome.html
# modified 17Nov2013 by Simon Walters @cymplecy to just change the way its called from other module

from smbus import SMBus

# Exception class for an I2C address out of bounds
class I2CaddressOutOfBoundsError(Exception):
    message = 'I2C Exception: I2C Address Out of Bounds'

# Exception class for a channel number out of bounds
class PCF8591PchannelOutOfBoundsError(Exception):
    message = 'PCF8591P Exception: ADC Channel Out of Bounds'

# Exception class for a DAC value out of bounds
class PCF8591PDACvalueOutOfBoundsError(Exception):
    message = 'PCF8591P Exception: DAC Output Value Out of Bounds'

class sgh_PCF8591P:

    # Constructor
    def __init__(self, busNum):
        print "init PCF8591"
        if busNum == 0:
            self.__bus = SMBus(0) # on a Rev 1 board
            #print "bus 0"
        else:
            self.__bus = SMBus(1) # on a Rev 2 board
        self.__addr = self.__checkI2Caddress(0x48)
        self.__DACEnabled = 0x00
        print self.readADC() # dummy call to raise exception if no chip presnt on the i2c bus
        print "PCF8591 init completed"
        
        # self.__bus = __i2cBus
        # self.__addr = self.__checkI2Caddress(__addr)
        # self.__DACEnabled = 0x00
        
   
# i2c = SMBus(0) # on a Rev 1 board
# # i2c = SMBus(1) # if on a Rev 2 board

# # Create a PCF8591P object
# sensor = PCF8591P(i2c, 0x48)
    
    # Read single ADC Channel
    def readADC(self, __chan = 0):
        __checkedChan = self.__checkChannelNo(__chan)
        self.__bus.write_byte(self.__addr, __checkedChan  | self.__DACEnabled)
        __reading = self.__bus.read_byte(self.__addr) # seems to need to throw away first reading
        __reading = self.__bus.read_byte(self.__addr) # read A/D
        return __reading
    
    # Read all ADC channels
    def readAllADC(self):
        __readings = []
        self.__bus.write_byte(self.__addr, 0x04  | self.__DACEnabled)
        __reading = self.__bus.read_byte(self.__addr) # seems to need to throw away first reading
        for i in range (4):
            __readings.append(self.__bus.read_byte(self.__addr)) # read ADC
        return __readings   
    
    # Set DAC value and enable output
    def writeDAC(self, __val=0):
        __checkedVal = self.__checkDACVal(__val)
        self.__DACEnabled = 0x40
        self.__bus.write_byte_data(self.__addr, self.__DACEnabled, __checkedVal)
    
    # Enable DAC output    
    def enableDAC(self):
        self.__DACEnabled = 0x40
        self.__bus.write_byte(self.__addr, self.__DACEnabled)
    
    # Disable DAC output
    def disableDAC(self):
        self.__DACEnabled = 0x00
        self.__bus.write_byte(self.__addr, self.__DACEnabled)
    
    # Check I2C address is within bounds
    def __checkI2Caddress(self, __addr):
        if type(__addr) is not int:
            raise I2CaddressOutOfBoundsError
        elif (__addr < 0):
            raise I2CaddressOutOfBoundsError
        elif (__addr > 127):
            raise I2CaddressOutOfBoundsError
        return __addr

    # Check if ADC channel number is within bounds
    def __checkChannelNo(self, __chan):
        if type(__chan) is not int:
            raise PCF8591PchannelOutOfBoundsError
        elif (__chan < 0):
            raise PCF8591PchannelOutOfBoundsError
        elif (__chan > 3):
            raise PCF8591PchannelOutOfBoundsError
        return __chan

    # Check if DAC output value is within bounds
    def __checkDACVal(self, __val):
        if type(__val) is not int:
            raise PCF8591PDACvalueOutOfBoundsError
        elif (__val < 0):
            raise PCF8591PDACvalueOutOfBoundsError
        elif (__val > 255):
            raise PCF8591PDACvalueOutOfBoundsError
        return __val

# Test harnesses
if __name__ == "__main__":

    from smbus import SMBus
    from time import sleep
    
    i2c = SMBus(0)

    try:
        sensor = PCF8591P()
    except Exception as e:
        print "Passed:  missing parameters" + e.message
    try:
        sensor = PCF8591P(i2c)
    except Exception as e:
        print "Passed:  missing address parameter" + e.message
    try:
        sensor = PCF8591P(i2c, 'cheese')
    except I2CaddressOutOfBoundsError as e:
        print "Passed:  " + e.message
    try:
        sensor = PCF8591P(i2c, -1)
    except I2CaddressOutOfBoundsError as e:
        print "Passed:  " + e.message
    try:
        sensor = PCF8591P(i2c, 128)
    except I2CaddressOutOfBoundsError as e:
        print "Passed:  " + e.message
    try:
        sensor = PCF8591P(i2c, 0x48)
    except Exception as e:
        print "Fail!!  Something went wrong!!" + e.message

    try:
        sensor.readADC()
        print "Passed:  default parameter"
    except PCF8591PchannelOutOfBoundsError as e:
        print "Fail!!  Something went wrong!!" + e.message
    try:
        print sensor.readADC(-1)
    except PCF8591PchannelOutOfBoundsError as e:
        print "Passed:  " + e.message
    try:
        print sensor.readADC(4)
    except PCF8591PchannelOutOfBoundsError as e:
        print "Passed:  " + e.message
    try:
        print sensor.readADC('cheese')
    except PCF8591PchannelOutOfBoundsError as e:
        print "Passed:  " + e.message

    try:
        sensor.writeDAC('chesse')
    except PCF8591PDACvalueOutOfBoundsError as e:
        print "Passed:  " + e.message
    try:
        sensor.writeDAC(-1)
    except PCF8591PDACvalueOutOfBoundsError as e:
        print "Passed:  " + e.message
    try:
        sensor.writeDAC(256)
    except PCF8591PDACvalueOutOfBoundsError as e:
        print "Passed:  " + e.message
    
    sensor.writeDAC(255)
    sleep(1)
    
    sensor.disableDAC()
    sleep(1)
    
    reading = sensor.readADC(0)
    print "0: {0}".format(reading)
    reading = sensor.readADC(1)
    print "1: {0}".format(reading)
    reading = sensor.readADC(2)
    print "2: {0}".format(reading)
    reading = sensor.readADC(3)
    print "3: {0}".format(reading)

    reading = sensor.readAllADC()
    print reading
    
    sensor.enableDAC()
    sleep(1)
    
    reading = sensor.readADC(0)
    print "0: {0}".format(reading)
    reading = sensor.readADC(1)
    print "1: {0}".format(reading)
    reading = sensor.readADC(2)
    print "2: {0}".format(reading)
    reading = sensor.readADC(3)
    print "3: {0}".format(reading)

    reading = sensor.readAllADC()
    print reading

    sensor.disableDAC()
    sleep(1)

    reading = sensor.readADC(0)
    print "0: {0}".format(reading)
    reading = sensor.readADC(1)
    print "1: {0}".format(reading)
    reading = sensor.readADC(2)
    print "2: {0}".format(reading)
    reading = sensor.readADC(3)
    print "3: {0}".format(reading)

    reading = sensor.readAllADC()
    print reading