PCIe-WDG-CSMA concept document

Low-profile half-length PCI Express card that performs advanced Watchdog and Computer Status Monitoring functions.

External Inputs
 - Dig In 0
 - Dig In 1
 - ISO In 0
 - ISO In 1
 - ISO In 2
 - ISO In 3

Outputs
 - Relay
 - FET 0
 - FET 1
 - TTL 0
 - TTL 1
 - WDG RESET
 - BUZZER
 - RGB LED

Input features: 
 - inputs can be individually put in "debounced" or "raw" mode; all subsequent operations described act on the raw or debounced data
 - debounced mode has programmable time-constant per input
 - inputs can be read "live" or latched [high|low|both|triggered], counted edges [rising|falling|both]
 - inputs can trigger Actions when selected condition(s) are met: rising|falling edges, high|low level, count threshold exceeded



Concept: 
 - A list of "Events"; each can trigger "Actions"

Events:
 - cold boot
 - warm boot caused by WDG
 - expected warm boot not caused by WDG
 - unexpected warm boot not caused by WDG
 - card warm reset
 - First Pet while not barking
 - Subsequent Pets
 - Growl [insufficient Pet frequency "warning"]
 - Bark [insufficient Pet frequency "alarm"]
 - First Pet after barking
 - input level high | low | rising | falling [for all input Causes, see note about 'debounce']
 - counter overflow | underflow
 - counter high speed warning/alarm threshold exceeded 
 - counter low speed warning/alarm threshold not met [missing pulse detector]
 - onboard 12V, 3.3V, ambient light, temperature, humidty: high/low warning/alarm thresholds and transitions
 - external temp warning/alarm transitions
 - 1 second tick

Actions: 
 - warm reset card 
 - enable event counter(s)
 - reset event counter(s)
 - trigger input latches
 - assert output state
	 - Output states[each output]: pulse [high|low][duration active][duration inactive][repeat count], level, inverted level, chirp, siren, .wav playback [_low_ max hz & short duration to reduce file-size]
 - increment counter[n]	 
 - decrement counter[n]
 - reload counter[n]
 - reset counter[n]
 
Action Lists, Action Groups, or Action Scripts:
 - Actions can be grouped into "Action Lists" or "Action groups" or "scripts" which can be invoked as if they were themselves Actions.
 - Several Factory Preset Action Lists, and several "user defined" Action Lists are stored in EEPROM. [8 total? xxx bytes total?]
	 - Factory Preset scripts cannot be modified by user
	 - One Factory Preset script is "PCI-WDG-CSM mode"



--------------------------------------------------------------
handle cold boot/warmboot/warmreset stuff
message processing loop
    read all inputs
    	read digital inputs and outputs into "raw" storage
    	read analog into "live" storage
    debounce ["non-debounced" just has a debounce counter reload value of "1", so it always copies as soon as it notices a difference]
    	if raw != live decrement debounce counter; if counter == 0, copy raw into live; reload debounce counter; 
	determine which subset of events have occurred from list of non-null event handler pointers 
		[determining if an event has occurred when no Action is pending wastes cpu time]
	determine set of Actions to fire as union of events-that-occurreds' handlers
		if more than one event that occurred has the same Action assigned, that action only occurs once
		
	Actions update "next_DO_data_raw" temporary state variables, not live hardware pins
	process PWM step
	update outputs to new values as calculated by Actions[in parallel, simultaneously, basically]
loop



PWM: 
	A single "PWM timer" increments from 0 to 100%.  Every PWM output with non-zero "number of pulses left to be generated" compares the counter to its "active duration" parameter, and if the PWM timer is less, the bit is set active; if the PWM timer is equal, the bit is set inactive and, if the pulse count isn't configured "forever" the pulse-count is decremented.

	struct {
		outputindex: byte;
		activeduration: word;
		n: word; // number of pulses left to be generated
	} PWM

Counter:
	A set of 16-bit up/down counters each with optional auto-reload.