The primary reason is to support the D4R-II with it's much faster PWM
frequency. The PWM RSSI code could not keep up, and since there are no
timers free for using capture compare of PWM signals in hardware one
solution is to use the ADC at a slow sample rate.
RC2 is used as before and it expects a signal between 0 and 3.3v. An
inline smoothing capacitor may help.
This commit also removes the cli command adc_power_channel since the
reading was never actually exposed anywhere.
Also support FrSky 1khz RSSI. See documentation also added in this
commit.
This commit also cleans up the PWM mapping code. 'mask' didn't need to
be a mask and it wasn't possible to add another 'type' since there were
only 4 possible values when it was a mask and they were already defined.
Combined with switching to using 16 bits instead of 8 for the mapping
configurations, it's now possible to have 256 types instead of 4 at the
expense of a few bytes of flash.
Moved the RSSI calculation into rx_common.c, previously it was in the
main loop.
This enables a new feature setting for PARALLEL_PWM which is enabled by
default.
This starts to move much of the feature checking/excluding code that is
littered through into a single place - validateAndFixConfig(). Since
the config is known to be valid after the method is called other code
can just get on with it's job instead of checking for confliciting
features/settings.
By decoupling everything the structures now only contain members they need. The mapping code is simplified. The calculation of timer periods is now where it belongs (with the output code, not with the mapping code). Also, since each motor output has it's own callback method it is technically possible to mix brushed and brushless motors if the brushed motors and brushless motors use different timers. Additional code would be required to fully support that.
