Difference between revisions of "Canvas EFIS Framework"

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The optional ''aural'' element can be any key of the aural configuration hash passed to MessageSystem.addAuralAlerts(). If the  
 
The optional ''aural'' element can be any key of the aural configuration hash passed to MessageSystem.addAuralAlerts(). If the  
  
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{
 
{
 
     msg: "Message Text",
 
     msg: "Message Text",
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var EICASMessages = [
 
var EICASMessages = [
 
     {msg: "APU FIRE", prop: "engines/engine[2]/on-fire", aural: "firebell"},
 
     {msg: "APU FIRE", prop: "engines/engine[2]/on-fire", aural: "firebell"},
     {msg: "AC 1 AUTOXFER", prop: "systems/AC/system[1]/serviceable", condition: {eq: 0}},
+
     {msg: "AC 1 AUTOXFER", prop: "systems/AC/system[1]/serviceable", condition: {eq: 0} },
     {msg: "AC BUS 1", prop: "systems/AC/outputs/bus1", condition: {lt: 100}},
+
     {msg: "AC BUS 1", prop: "systems/AC/outputs/bus1", condition: {lt: 100} },
 
     {msg: "ELT ON", prop: ""},
 
     {msg: "ELT ON", prop: ""},
 
];
 
];
</nowiki>
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|lang="nasal"}}
 
+
  
 
==== Class MessageClass ====
 
==== Class MessageClass ====

Revision as of 15:58, 13 February 2020

Contents

Foreword

The canvas EFIS framework (created by jsb) is by-product of the EFIS development done for the CRJ700 family, which uses Rockwell Collins Proline. It is published as a separate framework in the hope that it is useful for other aircraft as well, however some features may be rather specific. The biggest motivation and primary design goal was to support "near optimal" performance but that does not come automatically of course.

For the bigger picture see also Howto:Add an EFIS to your aircraft.

Introduction and Overview

An EFIS usually comprises multiple display units (DU for short; CRT or LCD screens) to show all the information relevant to the pilot (e.g. 2x PFD, 2x MFD, 2x EICAS in the CRJ700). Some displays like an EICAS / ECAM may show different pages for the systems of the aircraft, they can be select by the pilot via a corresponding control panel. Furthermore, displays can be swapped in case of a DU fault. In the CRJ700 the pilot can select display sources by turning the corresponding knobs.

The EFIS framework provides Nasal classes to handle the following:

Display unit

  • reference to a 3D object in the cockpit ("display unit") on which the canvas texture shall be displayed
  • power switch property
  • image source (canvas reference)

Note: Dimming of display can be done by defining an animation in the XML going with the 3D model of the DU. See example below.

Image source (EFISCanvas)

  • base class for EFIS/EICAS pages handling some SVG stuff
  • can load a SVG file and create clipping from <name>_clip elements
  • allows to register multiple update functions with individual update intervals
  • update functions can be en-/disabled by a single property that should reflect the visibility of the canvas (e.g. do not waste CPU with updating pages that are not currently displayed)
  • several listener factories for common animations like show/hide, translation, rotation

Display selectors / routing

  • Handle input events from cockpit knobs to switch displays / pages

EICAS Message system

  • Handle EICAS messages efficiently without eating up to much frame rate
  • Message queue: decouple canvas updates from message arrival

Thoughts on implementation

Design goal: EFIS framework should support best performance by offering different update methods and update rates for efficency.

Update rates

The EFIS/EICAS basically monitors the whole aircraft so it will have to read lots of properties. For efficiency the properties must be grouped into different classes already in the design phase, that is, the aircraft developer shall carefully think about how often a property changes. Some props are written to at frame rate by property rules but that does not mean the value changes every time. Furthermore, not every change has the same relevance, not everything needs to be displayed real time (= frame rate).

update rate Interval comment
2 0.500s low performance needs
10 0.100s low to med. performance but no fluent animation
20 0.050s
30 0.033s smooth canvas animation but possibly high performance need
60 0.017s

Some examples:

  • PFD contains many "real-time" elements like attitude indicator, speed, altitude etc. They should be updated probably at frame rate (min. 25 Hz) Other elements like radio frequency may be ok to update after 100ms or even 0.5s
  • An EICAS page displaying the door status maybe just fine with one update per second as doors move slowly and you won't see the door from outside and EICAS display inside the cockpit at the same time so a delay of one second does not matter

Update methods

  • Simple approach is to write an update loop that reads all relevant props, calculates the needed updates and updates the canvas elements (which in the end means writing properties) -> tends to be inefficient.
  • Property read/write is somehow "expensive" and can cost you a lot of frame rate. So the next better idea could be to limit the rate at which the update function is called - usually by a timer with some sensible interval.
  • If an animation is triggered only by one property and that property is unlikely to change often, remove the prop / animation from the update loop and use a listener instead. The listener may read other props as needed. A listener does not consume any CPU unless the property it listens to has changed, in which case the listener function is run.

Framework documentation

This section documents the framework classes and their methods.

Class EFIS

This is the top level class which ties together the different parts like display units, sources and cockpit controls.

new()

new(display_names, object_names, canvas_settings=nil);

Returns a new EFIS object

display_names
Vector of display names
object_names
Vector of 3D object names for canvas placement.
canvas_settings
Optional config hash for canvas that is merged with default settings of EFIS class

setPowerProp()

setPowerProp(path);

Creates listener for property path. Power on will start all display update functions, power of will stop them.

path
Property path to EFIS power property (bool).

setWindowSize()

setWindowSize(window_size);

Sets default size for canvas windows

window_size
Vector [size_x, size_y]

setDUPowerProps()

setDUPowerProps(power_props, minimum_power=0);

Sets default size for canvas windows

power_props
Vector of property paths, must be of same size as display_names given to new().
minimum_power
Passed to DisplayUnit.setPowerSource()

addSource()

addSource(efis_canvas);

Adds a EFISCanvas as display source, returns source ID to be used in mappings.

efis_canvas
A EFISCanvas instance created with EFISCanvas.new()

addDisplaySwapControl()

addDisplaySwapControl(ctrl, mappings, callback=nil);

Adds a listener for "ctrl", activates new source-display-mapping on change. Use this to implement a display swap knob in the cockpit.

callback
optional function that will be called with current ctrl value

addSourceSelector()

addSourceSelector(selected, target, sources=nil);

Adds a listener for "selected" which will read the target DU from "target" and sets its source according to "selected". Use this e.g. for a EICAS / ECAM page select panel.

sources
optional vector; selected -> source ID (as returned by addSource), defaults to all registered sources

setDefaultMapping()

setDefaultMapping(mapping);

Sets and activates a default mapping of sources to display units.

mapping
Vector [source_id1, source_id2, ...] or hash {DisplayName: source_id}

displayWindow()

displayWindow(id);

Opens display unit as canvas window.

id
Index of display


Class EFISCanvas

EFISCanvas manages a single canvas for you. It offers a bunch of little helpers to make the live of an aircraft developer easier. These helpers mostly do animation and update stuff on canvas elements in an efficient way.

new()

new(name, svgfile);

Returns a new EFISCanvas

name
Used e.g. in window title (see below)
svgfile
Filename of a SVG to load. (see also: loadsvg)

getPath()

returns path of canvas

getCanvas()

returns canvas instance

getRoot()

returns root group of the canvas

setUpdateN()

setUpdateN(node);

set a node that is checked in all registered update functions, they will only be run, if the value of this node is true

node
props.node object

loadsvg()

loadsvg(file);

Parses the given SVG file into the root group of the EFISCanvas. Clipping is setup for elements that have a corresponding element with the same name extended by "_clip".

file
filepath passed to canvas.parsesvg

addUpdateFunction()

addUpdateFunction(f, interval);

Creates a timer with given interval that runs the given function if the value of the update node is true.

f
Nasal function to run
interval
Interval in seconds

startUpdates()

Start all update timers.

stopUpdates()

Stop all update timers.

getInstr()

When updating EFIS displays, there is a need to access properties under /instrumentation very often. To avoid the rather expensive append operator ("~") and property path lookups, you should use this little helper. It creates node objects (only once) to access properties like "/instrumentation/"~sys~"["~id~"]/"~prop,

getInstr(sys, prop, default=0, id=nil);

Helper to quickly access instrumentation properties with this name schema: "/instrumentation/"~sys~"["~id~"]/"~prop

sys
the system name under /instrumentation
prop
default
Optional default value to return, if getValue() returns nil
id
Optional override the id of the current EFISCanvas obj (me.id)

updateTextElement()

updateTextElement(svgkey, text, color=nil);

Updates a single text element and optionally sets its color.

svgkey
Name of the text element to update.
text
new text, passed to setText()
color
Vector [r,g,b] or valid color name from EFISCanvas.colors

_updateClip()

private function that sets clipping for an element, if there is another element with the same name extended by "_clip".

Listener factories

Note

The following listener factories will return a function. The general usage is setlistener("/some/property/name", _makeListener_xxx(parameters), 1, 0);

As usual, the listened-to node is passed into the listener function as first argument and the function will getValue() and do something meaningful with the value.

The first argument to the listener factory functions is always svgkey which can be either a string naming one canvas element or a vector of such strings.


_makeListener_showHide()
_makeListener_showHide(svgkey, value=nil);

Returns listener to show/hide element(s).

svgkey
String or vector; the element(s) to update.
value
optional value to trigger show(); otherwise node.value will be implicitly treated as bool.
_makeListener_rotate()
_makeListener_rotate(svgkey, factors=nil);

Returns listener to rotate one or more canvas element(s) by property value. If svgkey is a vector, factors must be a hash having each elemnent in svgkey as a key and the corresponding factor.

svgkey
String or vector; the element(s) to update.
factors=nil
Factor for setRotation(value * factor); defaults to 1 if not given
_makeListener_translate()
_makeListener_translate(svgkey, fx, fy);

Returns listener to translate one or more canvas element(s) by property value. If svgkey is a vector, fx and fy must be hashes having each elemnent in svgkey as a key and the corresponding factor for translation.

svgkey
String or vector; the element(s) to update.
fx
Factor for translation in x direction
fy
Factor for translation in y direction
_makeListener_setColor()
_makeListener_setColor(svgkey, color_true, color_false);

Returns generic listener to change element color. Both color arguments can be either a vector [r,g,b] or a valid name (hash key) for EFISCanvas.colors;

svgkey
String or vector; element(s) on which to call setColor().
color_true
Color to use, if getValue() is true.
color_false
Color to use, if getValue() is false.
_makeListener_updateText()
_makeListener_updateText(svgkey, format="%s", default="");

Returns listener to update a canvas text element from property value.

svgkey
The element to update.
format
A valid format string for printf()
default
Value to use, if getValue() returns nil or false.


Methods of class DisplayUnit

This class is used by the EFIS class. DisplayUnit creates and places a canvas to a 3D object specified in new().

new()

new(name, canvas_settings, screen_obj, parent_obj = nil);

Configure the nasal file to load.

name
Used e.g. in window title (see below)
canvas_settings
passed to canvas.new()
screen_obj
used for canvas placement
parent_obj
used for canvas placement

setSource()

display_unit.setSource(path);

Select a canvas to show on the display unit.

path
A valid canvas path as returned by the canvas.getPath() method.

setPowerSource()

display_unit.setPowerSource(prop, min);

Sets a listener to prop. Display will show only if property value >= min

prop
Path to property that represents display power supply.
min
Minimum value of property to show display.

Example

var my_display_unit = DisplayUnit.new("PFD1");
# display turns on when DC power is >= 24 volts
my_display_unit.setPowerSource("/systems/DC/outputs/pfd1", 24);

asWindow()

display_unit.asWindow(window_size);

Opens the display in a canvas window.

window_size
Vector [size_x, size_y]; passed to canvas.Window.new().


EICAS message system

The message system decouples the update of canvas text elements (e.g. message lines) from the handling of messages. It is configured with the necessary message classes (e.g. warnings, caution messages, status messages) and a list of all possible messages. For each message a corresponding property can be defined that controls whether or not the message is shown. Alternatively, a message can be shown or hidden via the Nasal methods (see also the HOWTO section for examples and best practices).

Methods of class MessageSystem

new()
new(page_length, prop_path);

Creates a new message system.

page_length
Maximum page length. Page length can be changed at runtime but not exceed this initial value.
prop_path
Property path, some config and data of the message system will be put here.
setPowerProp()
setPowerProp(prop_path);

Sets a listener to the "power switch" property. Will call init() if property changes to true.

prop_path
Path to a bool property representing the EFIS power state.
addMessageClass()
addMessageClass(class_name, paging, color = nil);

Sets the number of lines per page.

lines
Number of lines per page
addMessages()
addMessages(class, messages);

Add message definitions to a class. Setup listeners according to message definitions that call setMessage() accordingly.

class
Class identifier returned by addMessageClass()
messages
Vector of message definitions. See below for format.
addAuralAlerts()
addAuralAlerts(alert_hash);

Set aural alert configuration hash

alert_hash
Hash; aural_name: {path: "myAircraft/Sounds", file: "sound.wav", volume: 1.0 }
setMessage()
setMessage(class, msg_id, visible=1);

Show or hide a message, optional trigger aural alert on show. Does nothing if message is already in desired state.

class
Class identifier returned by addMessageClass()
msg_id
see getMessageID()
visible
bool; 0 = hide, otherwise show
init()
init();

Used on power up to check for active messages. Enables sound queue for aural alerts.

hasUpdate()
hasUpdate();

Returns update flag.

setPageLength()
setPageLength(length);

Change page length. Length cannot exceed initial page length (see new())

length
New number of lines per page.
getPageLength()
getPageLength();

Returns current page length.

getFirstUpdateIndex()
getFirstUpdateIndex();

Returns the index of the first line that has changed.

getActiveMessages()
getActiveMessages();

Returns message queue and clears the hasUpdate flag.

getMessageID()
getMessageID(class, msg_text);

Returns numeric id for a message in given class.

class
Class identifier returned by addMessageClass()
msg_text
Message string to search for.
disableMessage()
disableMessage(class, msg_id);

Inhibit message (or all messages in class if no msg_id is given).

class
Class identifier returned by addMessageClass()
msg_id
see getMessageID()
enableMessage()
enableMessage(class, msg_id);

Re-enable message (or all messages in class if no id is given).

class
Class identifier returned by addMessageClass()
msg_id
see getMessageID()

-- following methods are for message output on a canvas --

setCanvasGroup()
setCanvasGroup(group);

Set an existing canvas group to create text elements on.

group
A valid canvas group element
createCanvasTextLines()
createCanvasTextLines(left, top, line_spacing, font_size);

Show or hide a message, optional trigger aural alert on show. Does nothing if message is already in desired state.

left, top
Position of text element.
line_spacing
see getMessageID()
font_size
Font size.
createPageIndicator()
createPageIndicator(left, top, font_size, format_string = nil);

Creates a text element for a page indicator on the canvas group set with setCanvasGroup().

left, top
Position of text element
font_size
Font size.
format_string
Optional printf format string, defaults to "Page %2d/%2d"
updateCanvas()
updateCanvas();

Call this regularly to update text lines on canvas with the content of the message queue.

updatePageIndicator()
updatePageIndicator(current, total);

Updates the page indicator text element.

current
Currently displayed page.
total
Total number of pages.


Format for message definitions

MessageSystem.addMessages() expects a vector of message definitions. A message definition is a hash with the keys msg, prop, aural, condition (only msg is required, the rest is optional).

prop shall be used if

  1. the visibility of a message depends on only one property
  2. this property does NOT change frequently

The optional condition element reqires prop and is again a hash where you can define up to four compare values. For each existing key a listener to prop will be created performing the selected comparision. It is up to the developer to provide a reasonable configuration here.

The optional aural element can be any key of the aural configuration hash passed to MessageSystem.addAuralAlerts(). If the

{
    msg: "Message Text",
    prop: "/some/bool/trigger", # optional
    aural: "sound_name",        # optional
    condition: {                # optional
        eq: "foo",
        ne: "bar",
        lt: 21, # "less than",
        gt: 42, # "greater than",
    },
}
# example:
var EICASMessages = [
    {msg: "APU FIRE", prop: "engines/engine[2]/on-fire", aural: "firebell"},
    {msg: "AC 1 AUTOXFER", prop: "systems/AC/system[1]/serviceable", condition: {eq: 0} },
    {msg: "AC BUS 1", prop: "systems/AC/outputs/bus1", condition: {lt: 100} },
    {msg: "ELT ON", prop: ""},
];

Class MessageClass

Helper class for MessageSystem. Stores configuration data for a message class.

Class Pager

Helper class for MessageSystem. The pager class takes a vector of messages and splits it into pages (sub vectors of defined length). It can be configured via the Nasal methods described below or via some properties on the fly.

Config nodes

property name Type and access Description
page_length (INT, r/w) maximum number of lines per page.
page (INT, r/w) currently selected page.
pages (INT, r/o) number of pages according to last run of the page() method.
new()
new(page_length, prop_path);

Configure the nasal file to load.

page_length
Maximum lines per page.
prop_path
Property base path; pager configuration nodes will be created under this path.
page()
page(lines);

Return lines of current page; sticky messages will not be paged.

lines
Vector of messages
pageChanged()
pageChanged();

Return the page-changed flag and resets it to false, so calling this method again will return false unless another page has been selected in the meantime.

setPageLength()
setPageLength(lines);

Update the value of the page_length node (the number of lines per page).

lines
Number of lines per page
setPage()
setPage(page);

Update the value of page node used by page() to return the right lines.

page
Selected page
getPageCount()

Returns total number of pages, according to last run of page()

getCurrentPage()

Returns current page, according to last run of page()

HOWTO and Examples

to be written / reference implementation in CRJ700 familiy to be published after framework is published.