SRV_Channel: use enumeration for servo input type

[peterbarker]

No description provided.

[IamPete1]

Why start at 16?

[peterbarker]

Better than zero :-) I'd usually wouldn't choose 16, but on this day I did. Since it's an internally-used enumeration the values don't matter, and if you're stepping through gdb and find the number 17 it's a lot easier to search for that value in the relevant header vs 0 or 1.

[tridge]

needs to be RANGE=0 to be sure that the default is the same

[peterbarker]

I've done this by setting the value in the constructor to Type::Range. Changing the enumeration values here wouldn't have helped.

[magicrub]

So, what output type is aux output?

[peterbarker]

So, what output type is aux output?

Comes down to "whatever the library responsible for the pin wants it to be". For example, NeoPixel does digital stuff on the pins it owns (k_LED_neopixel1 etc) - IOW it isn't even doing pwm on those pins. It's up to the handling code to set the range/angle if they want to do PWM output and specify the output level using a range or angle value. If you look at AP_Gripper_Servo.cpp you'll see that it sets the pwm output level directly.

Breaking this out into a distinct enumeration value is meant to help catch where we set things with the angle calls but haven't specified a range for the angles...