There are two hardware PWM channels on the BCM2385/6. PWM0, which can be set to use GPIOs 12, 18, 40, and 52. Only 12 (pin 32) and 18 (pin 12) are available on the B+/2B, and PWM1 which can be set to use GPIOs 13, 19, 41, 45 and 53. Only 13 is available on the B+/2B, on pin 35 (but I think PWM1 is ...