i was thinking of starting by having a hover mode, indoors : fix a safe throttle that is able to lift off. doesn't matter if the quadrotor falls gradually, i just want to make sure my imu and attitude estimation algorithm is stable; that the quadrotor doesn't wobble left right up down or drift in this mode. the purpose is to make it stay in a small circle.
hence, xbee will be used for simple commands like start moving. land gradually and stop the motor.
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but its a serial transmission, best and saefest way is using the API-mode!
I send commands in four bytes, in some case packed as 7byte-hammingcode for highest saefty:
rudder (direction) 8bit
gas (pitch) 7bit and multiplex with the rest some 7 (or with slow-rate for ships 127) switches or aditionaly prop-channel.
elevator (nick) 8bit
aileron 8bit
telemetrie is send back also as 7byte-hamming-code, with two bytes descriptor and two payload. this works well with the logview-openformat SW to visualize it..
after decoding the date is send over a two-wire bus to the actor-nods, they generates the servo-impulses.
an actor-nod is free progammable, with his own powersupply and some telemetrie-functionality.
I take advantage of a arduino-mini-pro, can bind up to 16 servos or with multiplexer much more!
also has done this job with ATtiny13 or 15, but they are very limited..
one type of hardware, the actor-nod, due all jobs, on the ground a arduino (or FEZ) digitalize the sticks and switches, displays telemetrie and warnings.
in simpler models I use only the funnel, works as one2one replacement of a "traditional" reciver.
I attach a switched-DCconverter to generate the 5V-6A for digiservos, its very compact!
for slope-planes one funnel in the fuslage and one in every wing, connected wireless as 802-network. so you gain more saefty by a multidirectional-antenna-orientation.
on board of complex models a busmaster with the xbee (funnel is perfect for that) act as router to the other nods: programmed as left-wing-nod, right-wing-nod, fuslage-nod, telemetrie-nod and one as autopilot-nod. I use ardupilot and be very kind with the results. only four wires goes trough the model, two-wires data and two with energy, mostly on 7-8VDC (2s lipo).
this speedup the wiring, safe much weight and prevent EMV-issues..
its very simple to use a WIFI or bluetooth-module, only a lil-part of the busmaster-code is to change. for indoor-use bluetooth will give best satisfaction, works also for most of my lil-planes
however, the rc controllers have a latency of average 30-40 ms for a Spektrum radio, which is much longer than xbee link.
please see this link http://rc.runryder.com/helicopter/t172571p1/
and see reference picture attached.
Please correct me if i'm wrong.
thanks in advance =)
rc latency.gif