Source Code for Module PCA9685

 1  # PCA9685.py 
 2  # ============================================================================ 
 3  # Most code from Adafruit PCA9685 16-Channel PWM Servo Driver 
 4  # with thanks to the author 
 5  # ============================================================================ 
 6   
 7  import time 
 8  import math 
 9  from Tools import Tools 
10   
11 -class PWM: 
12      _mode_adr              = 0x00 
13      _base_adr_low          = 0x08 
14      _base_adr_high         = 0x09 
15      _prescale_adr          = 0xFE 
16   
17 -    def __init__(self, bus, address = 0x40): 
18          ''' 
19          Creates an instance of the PWM chip at given i2c address. 
20          @param bus: the SMBus instance to access the i2c port (0 or 1). 
21          @param address: the address of the i2c chip (default: 0x40) 
22          ''' 
23          self.bus = bus 
24          self.address = address 
25          self._isAvailable = True 
26          self._writeByte(self._mode_adr, 0x00) 
27   
28 -    def setFreq(self, freq): 
29          ''' 
30          Sets the PWM frequency. The value is stored in the device. 
31          @param freq: the frequency in Hz (approx. in range 16 - 1500 Hz) 
32          ''' 
33          if not self._isAvailable: 
34              return 
35          prescaleValue = 25000000.0    # 25MHz 
36          prescaleValue /= 4096.0       # 12-bit 
37          prescaleValue /= float(freq) 
38          prescaleValue -= 1.0 
39          prescale = math.floor(prescaleValue + 0.5) 
40          oldmode = self._readByte(self._mode_adr) 
41          if oldmode == None: 
42              return 
43          newmode = (oldmode & 0x7F) | 0x10  # sleep 
44          self._writeByte(self._mode_adr, newmode)  # goto sleep 
45          self._writeByte(self._prescale_adr, int(math.floor(prescale))) 
46          self._writeByte(self._mode_adr, oldmode) 
47          time.sleep(0.005) 
48          self._writeByte(self._mode_adr, oldmode | 0x80) 
49   
50 -    def setDuty(self, channel, duty): 
51          ''' 
52          Sets a single PWM channel. The value is stored in the device. 
53          @param channel: one of the channels 0..15 
54          @param duty: the duty cycle 0..4095 (included) 
55          ''' 
56          if not self._isAvailable: 
57              return 
58          duty = int(duty) 
59          duty = max(0, duty) 
60          duty = min(4095, duty) 
61          self._writeByte(self._base_adr_low + 4 * channel, duty & 0xFF) 
62          self._writeByte(self._base_adr_high + 4 * channel, duty >> 8) 
63   
64 -    def _writeByte(self, reg, value): 
65          try: 
66              self.bus.write_byte_data(self.address, reg, value) 
67          except: 
68              Tools.debug("Error while writing to I2C device at address: " + str(self.address)) 
69              self._isAvailable = False 
70   
71 -    def _readByte(self, reg): 
72          try: 
73              result = self.bus.read_byte_data(self.address, reg) 
74              return result 
75          except: 
76              Tools.debug("Error while reading from I2C device at address: " + str(self.address)) 
77              return None 
78