TODO

save 4WS mix to model config (selectable)
add function to disable/enable steering D/R to make it really dualrate
    (or leave it to extended multi-position ?)
do one timer model specific (selectable)
add throttle hold button function
MultiPosition for all trim functions (except lists == MultiPosition)
ARC - Adjustable Rate Control
    - two linear curves with settable point and rate
    - for steering, forward and back
steering speed with 2 settings and point where it changes
losikid
    ? timer down settings in smaller increments (not whole minutes)
    ? timer down beeps 60s(1) 30s(2) 15s(3) 10-1s(each) 0s(rapid beeping)
    ? changing saved value when at momentary-state
    ? MultiPosition momentary keys + changing values with trims
    ? default value for DIG mix
? RS232 communication to get/set global/model config data

? PPM input for head tracking gyro
    - pin PD7 TLI non-maskable interrupt at signal edge
    - or pin PD1 (SWIM), PD5, PD6 with pin change interrupt at signal edge
	- set timer_interrupt and ppm_interrupt to lower level as it
	  can be interrupted by PPM in signal
    - read timer register, ppm_timer to cyclic buffer
	- problem with determining if timer interrupt already incremented
	  ppm_timer or not
	    - timer_interrupt
		- store ppm_timer to ppm_timer_old
		- set bit flag ppm_timer_incrementing
		- increment ppm_timer
		- clear bit flag ppm_timer_incrementing
	    - ppm_input_interrupt
		- read ppm_timer
		- if bit flag ppm_timer_incrementing is set
		    - compare ppm_timer with ppm_timer_old
			- if same, increment readed ppm_timer value
    - wakeup PPM_INPUT task
	- read values from cyclic buffer
	- compute PPM servo signals and assign them to ppm_in variables
    - in menu set mapping of channels to PPM INPUT channels



Some suggestions taken from manuals of other radios:

programmable mixes
throttle speed 1-3 SPEED 1-100%, trigger points 1-100
throttle acceleration
brake acceleration
throttle curves EXP/VTR/CRV
start function
engine cut function
ABS 
    amount of brake return 0-100%
    delay 0-1.4s
    cycle speed 1-30
    trigger point 10-100
    cycle duty ratio -3..3
    steering mixing N10-100, E10-100
brake mixing
boat tilt mixing
neutral brake
throttle mode FWD50/BRK50 or FWD70/BRK30
throttle Idle-Up 0-50%


other:
PC editor
digital/custom switches (set when some conditions are satisfied)