The datasheet shows register 250 is "ALL" pins, which corresponds to
virtual pin 61 (61*4+6=250). Pin 61 was already allowed with PWM
command for OFF and ON, but not specified pwm values. This update
allows virtual pin 61 to be assigned pwm values for all channels.
Example usage to set all channels to 2500:
`driver15 pwm,61,2500`
The INVERT option makes PWM and ON/OFF values meaningful for open-drain connected lights.
- Activate with: driver15 invert 1
- PWM value is inverted, so 0 is "off" and 4096 is "on"
- INVERT is included in status and telemetry