The RaspberryPi hardware supports 2 hardware PWM channels. But as Pi4J uses PiGPIO “under the hood”, we can take advantage of the
The Raspberry Pi supports 2 hardware based PWM channels. You can access these two channels via 2 separate sets of 4 GPIO header pins. But still limited to only 2 channels (2 unique PWM timing configurations).
The same PWM channel is available on multiple GPIO. The latest frequency and dutycycle setting will be used by all GPIO which share a PWM channel. The GPIO must be one of the following: 12 PWM channel 0 All models but A and B 13 PWM channel 1 All models but A and B 18 PWM channel 0 All models 19 PWM channel 1 All models but A and B 40 PWM channel 0 Compute module only 41 PWM channel 1 Compute module only 45 PWM channel 1 Compute module only 52 PWM channel 0 Compute module only 53 PWM channel 1 Compute module only
As Pi4J is using PiGPIO “under the hood”, you can take advantage of the additional PWM functionalities of it. PiGPIO is providing additional (soft) PWM support to any of the GPIO pins (0-31) and its using some hardware timing technique to optimize performance — but its not the same as the actual hardware PWM pins natively on the RaspberryPi. In the Pi4J API, we call this “Software” PWM and you would need to set
.pwmType(PwmType.SOFTWARE). We consider this software-based PWM because its being provided at a software layer, in this case by the PIGPIO library.
If you need more than 2 PWM pins, use the software PWM functionality, it may be perfectly fine for your application. If they are not good enough, then you will probably need a PWM expander board/chip (controlled by I2C/SPI) to provide additional PWM support.
!! TODO add example code