Squashed commits:
[ed2a243] FlightTasks: Preserve control loop tuning when applying max altitude limit
[b33b947] FlightTasks: Add terrain hold function
This new mode of altitude control uses terrain following when holding position and normal altitude control when moving.
Rather than initializing the rssi percentage lookup table at runtime
on the heap, we would like it to be stored in flash.
This change pre-computes the rssi lookup table.
On SPM4649T receivers with firmware versions at least 1.1RC9, the
serial data will contain an rssi value in dbm, as outlined in the
Remote Receiver Interfacing document section 8.3.1.
If the value received is greater than or equal to zero, the receiver
does not support rssi data, and the incoming value will be ignored.
However, if the value is negative, we can use the rssi value.
When we have a valid rssi, it gets mapped to a percentage from 0 to
100 as expected by mavlink. This mapping is constructed as a
logarithmic function over Spektrum's published minimum and maximum
rssi values, -92dBm to -42dBm as 0 to 100:
100 Log10[1 + (x - min) * (9 / (max - min))]
This change updates all calls to the dsm input rountes to return
the rssi value.
Note that one place this doesn't work with the px4io enabled.
There is a comment left in the absence of analog rssi that:
"we do not actually get digital RSSI regs[PX4IO_P_RAW_RC_NRSSI]".
This restriction has been left in place, as removing it exposes a
problem where the frequency of the control tick is greater than
that of valid dsm frames so the rssi isn't valid every cycle.
More than a year ago I started the easy to use math::Functions to handle
the always used mathematical SISO functions to be tested and available.
I switched x, y and z stick input to the freesh programmed deadzone and
exponential functions from the library to unify and clarify their use.
I just realized yaw was left over because it lead to a drift problem in
certain new use cases.
Now I'm just adding the yaw stick to the already well working method.
Daniel Agar