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| 1 | from time import sleep | |
| 2 | ||
| 3 | # relevant registers | |
| 4 | MODE1 = 0x00 | |
| 5 | MODE2 = 0x01 | |
| 6 | LED = 0x06 | |
| 7 | ALL_LED = 0xFA | |
| 8 | PRE_SCALE = 0xFE | |
| 9 | ||
| 10 | class Pca9685: | |
| 11 | def __init__( self, bus, addr ): | |
| 12 | self.addr = 0b1000000 | addr | |
| 13 | self.bus = bus | |
| 14 | self.write_reg( MODE1, 1 << 5 ) # initialize MODE1 register | |
| 15 | sleep( 500e-6 ) # wait 500us to allow oscillator to power up | |
| 16 | ||
| 17 | def read_reg( self, reg ) | |
| 18 | return self.read_regs( reg, 1 )[0] | |
| 19 | ||
| 20 | def write_reg( self, reg, value ): | |
| 21 | return self.write_regs( reg, [ value ] ) | |
| 22 | ||
| 23 | def read_regs( self, reg, count ): | |
| 24 | assert reg in range( 0, 256 ) | |
| 25 | assert count in range( 1, 257-reg ) | |
| 26 | return self.bus.read_i2c_block_data( self.addr, reg, count ) | |
| 27 | ||
| 28 | def write_regs( self, reg, values ): | |
| 29 | assert reg in range( 0, 256 ) | |
| 30 | return self.bus.write_i2c_block_data( self.addr, reg, values ) | |
| 31 | ||
| 32 | def get_pwm( self, output ): | |
| 33 | assert output in range( 0, 16 ) | |
| 34 | reg = LED + 4 * output | |
| 35 | ||
| 36 | [ on_l, on_h, off_l, off_h ] = self.read_regs( reg, 4 ) | |
| 37 | on = on_l | on_h << 8 | |
| 38 | off = off_l | off_h << 8 | |
| 39 | ||
| 40 | phase = on | |
| 41 | duty = ( off - on ) & 0xfff | |
| 42 | if off & 0x1000: | |
| 43 | duty = 0 | |
| 44 | elif on & 0x1000: | |
| 45 | duty = 4096 | |
| 46 | ||
| 47 | return ( duty, phase ) | |
| 48 | ||
| 49 | def set_pwm( self, output, duty, phase=0 ): | |
| 50 | assert duty in range( 0, 4097 ) | |
| 51 | assert phase in range( 0, 4096 ) | |
| 52 | ||
| 53 | if output == 'all': | |
| 54 | reg = ALL_LED | |
| 55 | else: | |
| 56 | assert output in range( 0, 16 ) | |
| 57 | reg = LED + 4 * output | |
| 58 | ||
| 59 | on = phase | |
| 60 | off = ( duty + phase ) & 0xfff | |
| 61 | if duty == 0: | |
| 62 | off |= 0x1000 | |
| 63 | elif duty == 4096: | |
| 64 | on |= 0x1000 | |
| 65 | ||
| 66 | on_l = on & 0xff | |
| 67 | on_h = on >> 8 | |
| 68 | off_l = off & 0xff | |
| 69 | off_h = off >> 8 | |
| 70 | self.write_regs( reg, [ on_l, on_h, off_l, off_h ] ) |
