Source Code for Module PCF8591

 1  # PCF8591.py 
 2   
 3  import smbus 
 4  import RPi.GPIO as GPIO 
 5  from Tools import Tools 
 6   
 7 -class ADC: 
 8 -    def __init__(self, channel, address = 0x48): 
 9          ''' 
10          Creates an instance of the chip at given i2c address. 
11          @param bus: the SMBus instance to access the i2c port (0 or 1). 
12          @param channel: the channel to read (0..3) 
13          @param address: the address of the i2c chip (default: 0x48) 
14          ''' 
15          self._isSMBusAvailable = True 
16          try: 
17              if GPIO.RPI_REVISION > 1: 
18                  self._bus = smbus.SMBus(1)  # For revision 2 Raspberry Pi 
19                  Tools.debug("Found SMBus for revision 2") 
20              else: 
21                  self._bus = smbus.SMBus(0)  # For revision 1 Raspberry Pi 
22                  Tools.debug("Found SMBus for revision 1") 
23          except: 
24              print "No SMBus found on this robot device." 
25              return 
26          self._isSMBusAvailable = False 
27          self._address = address 
28          # set control register to read specified channel 
29          self._bus.write_byte(address, channel) 
30   
31   
32 -    def getValue(self): 
33          ''' 
34          Reads the specified channel and returns the value (0..255). 
35          @return the byte value or None, if an error occurred 
36          ''' 
37          if self._isSMBusAvailable: 
38              return None 
39          return self._bus.read_byte(self._address) 
40