diff options
| author | Anatoli Arkhipenko <arkhipenko@hotmail.com> | 2015-12-23 17:04:21 -0500 |
|---|---|---|
| committer | Anatoli Arkhipenko <arkhipenko@hotmail.com> | 2015-12-23 17:12:06 -0500 |
| commit | 965f1b768d3d0675e2483ca62fa6d0565c389a31 (patch) | |
| tree | 8bae4e1eee8275efaab252b35cb26c6a304fb015 /extras/TaskScheduler.html | |
| parent | 42d8d776e3fdb3c48700a3d88c8615dbf81da23f (diff) | |
Version 2.0.0 support for layered task prioritizationv2.0.0
* _TASK_PRIORITY - support for layered task prioritization
Diffstat (limited to 'extras/TaskScheduler.html')
| -rw-r--r-- | extras/TaskScheduler.html | 599 |
1 files changed, 455 insertions, 144 deletions
diff --git a/extras/TaskScheduler.html b/extras/TaskScheduler.html index 699c110..5c5edc8 100644 --- a/extras/TaskScheduler.html +++ b/extras/TaskScheduler.html @@ -6,7 +6,7 @@ <META NAME="GENERATOR" CONTENT="LibreOffice 3.5 (Linux)"> <META NAME="CREATED" CONTENT="20150206;16300000"> <META NAME="CHANGEDBY" CONTENT="Anatoli Arkhipenko"> - <META NAME="CHANGED" CONTENT="20151128;23410000"> + <META NAME="CHANGED" CONTENT="20151223;16480000"> <META NAME="Info 1" CONTENT=""> <META NAME="Info 2" CONTENT=""> <META NAME="Info 3" CONTENT=""> @@ -15,7 +15,7 @@ <!-- @page { margin: 0.79in } P { margin-bottom: 0.08in; direction: ltr; color: #000000; widows: 0; orphans: 0 } - P.western { font-family: "Liberation Serif", "Times New Roman", serif; font-size: 12pt; so-language: en-US } + P.western { font-family: "Liberation Serif", "MS PMincho", serif; font-size: 12pt; so-language: en-US } P.cjk { font-family: "WenQuanYi Micro Hei", "MS Mincho"; font-size: 12pt; so-language: zh-CN } P.ctl { font-family: "Lohit Hindi", "MS Mincho"; font-size: 12pt; so-language: hi-IN } A:link { color: #0000ff } @@ -25,10 +25,10 @@ <BODY LANG="en-US" TEXT="#000000" LINK="#0000ff" BGCOLOR="#ffffff" DIR="LTR"> <P CLASS="western" STYLE="margin-bottom: 0in"><FONT SIZE=4 STYLE="font-size: 15pt"><B>Task Scheduler</B></FONT></P> -<P CLASS="western" STYLE="margin-bottom: 0in"><B>cooperative +<P CLASS="western" STYLE="margin-bottom: 0in"><B>Cooperative multitasking for Arduino microcontrollers</B></P> <P CLASS="western" STYLE="margin-bottom: 0in; border-top: none; border-bottom: 1px solid #000000; border-left: none; border-right: none; padding-top: 0in; padding-bottom: 0.01in; padding-left: 0in; padding-right: 0in"> -<FONT SIZE=2 STYLE="font-size: 11pt"><B>Version 1.9.2: 2015-12-20</B></FONT></P> +<FONT SIZE=2 STYLE="font-size: 11pt"><B>Version 2.0.0: 2015-12-23</B></FONT></P> <P CLASS="western" STYLE="margin-bottom: 0in"><BR> </P> <P CLASS="western" STYLE="margin-bottom: 0in"><B>OVERVIEW</B>:</P> @@ -55,6 +55,8 @@ supporting:</P> <LI><P CLASS="western" STYLE="margin-bottom: 0in">Support for Local Task Storage pointer (allowing use of same callback code for multiple tasks)</P> + <LI><P CLASS="western" STYLE="margin-bottom: 0in">Support for + layered task prioritization</P> </OL> <P CLASS="western" STYLE="margin-bottom: 0in"><BR> </P> @@ -92,6 +94,13 @@ processed by the <B>Scheduler</B> in the order they were added (linked together).</P> <P CLASS="western" STYLE="margin-bottom: 0in"><BR> </P> +<P CLASS="western" STYLE="margin-bottom: 0in"><B>Starting with +version 2.0.0 TaskScheduler supports task prioritization. Please +refer to the specific chapter of this manual for details on layered +prioritization. </B> +</P> +<P CLASS="western" STYLE="margin-bottom: 0in"><BR> +</P> <P CLASS="western" STYLE="margin-bottom: 0in">Each task performs its function via a callback method. Scheduler calls Task’s callback method periodically until task is disabled or runs out of iterations. @@ -126,14 +135,14 @@ than the Scheduler's <B>execute</B>() method).</P> </P> <P CLASS="western" STYLE="margin-bottom: 0in; page-break-after: avoid"> <B>Below is the flowchart of a Task lifecycle:</B></P> -<P CLASS="western" STYLE="margin-bottom: 0in"><IMG SRC="TaskScheduler_html.png" NAME="graphics1" ALIGN=BOTTOM WIDTH=664 HEIGHT=570 BORDER=0></P> +<P CLASS="western" STYLE="margin-bottom: 0in"><IMG SRC="TaskScheduler_html.png" NAME="graphics1" ALIGN=BOTTOM WIDTH=664 HEIGHT=517 BORDER=0></P> <P CLASS="western" STYLE="margin-bottom: 0in"><BR> </P> <P CLASS="western" STYLE="margin-bottom: 0in"><B>TaskScheduler</B> library maybe compiled with different compilation controls enabled/disabled. This is a way to limit TaskScheduler functionality (and size) for specific purpose (sketch). This is achieved by -defining specific #<B>define</B> paramenters <I>before</I> +defining specific #<B>define</B> parameters <I>before</I> TaskScheduler.h header file. Specifically:</P> <P CLASS="western" STYLE="margin-bottom: 0in"><BR> </P> @@ -150,7 +159,7 @@ tasks in the chain always requires immediate execution (aInterval = execution.</P> <P CLASS="western" STYLE="margin-bottom: 0in"><BR> </P> -<P CLASS="western" STYLE="margin-bottom: 0in"><B>Note: </B>Task +<P CLASS="western" STYLE="margin-bottom: 0in"><B>NOTE: </B>Task Scheduler uses <B>millis()</B> to determine if tasks are ready to be invoked. Therefore, if you put your device to any “deep” sleep mode disabling timer interrupts, the <B>millis()</B> count will be @@ -209,10 +218,10 @@ scheduled, and where next execution time of the task falls. Two methods provide this information. </P> <P CLASS="western" STYLE="margin-bottom: 0in"><B>Task::getStartDelay() -</B><SPAN STYLE="font-weight: normal">method: return number of -milliseconds between current system time (millis) and point in time -when the task was scheduled to start. A value of 0 (zero) indicates -that task started right on time per schedule. </SPAN> +</B>method: return number of milliseconds between current system time +(millis) and point in time when the task was scheduled to start. A +value of 0 (zero) indicates that task started right on time per +schedule. </P> <P CLASS="western" STYLE="margin-bottom: 0in"><B>Task::getOverrun()</B> method: If <B>getOverrun </B>returns a negative value, this Task’s @@ -260,9 +269,9 @@ anything hardware dependent) can be blocked (or hung), by failed hardware. In this case, a watchdog timer could be employed to trap such a failed task, and identify which one (by task id) and where in the task (by a control point) the problem is likely located.</P> -<P CLASS="western" STYLE="margin-bottom: 0in"> +<P CLASS="western" STYLE="margin-bottom: 0in"><BR> </P> -<P CLASS="western" STYLE="margin-bottom: 0in"><B>Note: </B>by +<P CLASS="western" STYLE="margin-bottom: 0in"><B>NOTE: </B>by default, talk IDs are assigned sequentially (1, 2, 3, …) to the tasks as they are being created. Programmer can assign a specific task id. <B>Task ids are unsigned integers.</B></P> @@ -295,6 +304,17 @@ enabled by placing appropriate #define statements in front of the #include statement for the TaskScheduler header file.</P> <P CLASS="western" STYLE="margin-bottom: 0in"><BR> </P> +<P CLASS="western" STYLE="margin-bottom: 0in">#define <B>_TASK_PRIORITY</B></P> +<P CLASS="western" STYLE="margin-bottom: 0in">…will compile +TaskScheduler with support for layered task prioritization. Task +prioritization is achieved by creating several schedulers, and +organizing them in priority layers. Tasks are assigned to schedulers +corresponding to their priority. Tasks assigned to the “higher” +layers are evaluated for invocation more frequently, and are given +priority in execution in case of the scheduling coincidence. More +about layered prioritization in the API documentation and +TaskScheduler examples. +</P> <P CLASS="western" STYLE="margin-bottom: 0in"><BR> </P> <P CLASS="western" STYLE="margin-bottom: 0in"><BR> @@ -303,28 +323,163 @@ enabled by placing appropriate #define statements in front of the </P> <P CLASS="western" STYLE="margin-bottom: 0in"><B>TASK PRIORITY AND COOPERATIVE MULTITASKING:</B></P> -<P CLASS="western" STYLE="margin-bottom: 0in">TaskScheduler <B>does -not support</B> task priority functionality. I have been thinking a -lot about it (especially since Symbian's Active Objects, which -TaskScheduler is inspired by, support it), but decided against it. +<P CLASS="western" STYLE="margin-bottom: 0in"><BR> +</P> +<P CLASS="western" STYLE="margin-bottom: 0in">Starting with version +2.0.0 TaskScheduler supports task prioritization. Priority is +associated with a <B>Scheduler</B>, not individual <B>Tasks</B>, +hence the concept of priority layers. Tasks subsequently are assigned +to schedulers corresponding to their desired priority. The lowest +priority Scheduler is called “<B>base scheduler</B>” or “<B>base +layer</B>”. Let’s call higher priority schedulers by their +priority number, with larger number corresponding to higher priority +of task execution. </P> <P CLASS="western" STYLE="margin-bottom: 0in"><BR> </P> -<P CLASS="western" STYLE="margin-bottom: 0in">This is why:</P> +<P CLASS="western" STYLE="margin-bottom: 0in">Task prioritization is +achieved by executing the entire chain of tasks of the higher +priority scheduler for every single step (task) of the lower priority +chain. <B>Note</B> that actual callback method invocation depends on +priority <B>and </B>the timing of task schedule. However, higher +priority tasks are evaluated more frequently and are given priority +in case of scheduling collision. +</P> <P CLASS="western" STYLE="margin-bottom: 0in"><BR> </P> <P CLASS="western" STYLE="margin-bottom: 0in"><BR> </P> +<P CLASS="western" STYLE="margin-bottom: 0in">For most tasks +TaskScheduler <B>does not need </B>task priority functionality. +Prioritization requires additional scheduling overhead, and should be +used only for critical tasks.</P> <P CLASS="western" STYLE="margin-bottom: 0in"><BR> </P> -<P CLASS="western" STYLE="margin-bottom: 0in">1. Execution chains are -simple and efficient. The main idea is to minimize scheduling -overhead by Scheduler going through the chain. Implementing true -priority would require looking ahead through the entire chain, -ranking and aging tasks by priorities. It would slow the <FONT FACE="FreeMono, MS Mincho, monospace"><FONT SIZE=2 STYLE="font-size: 10pt">execute() -</FONT></FONT>loop significantly.</P> +<P CLASS="western" STYLE="margin-bottom: 0in">A few points on that:</P> <P CLASS="western" STYLE="margin-bottom: 0in"><BR> </P> +<P CLASS="western" STYLE="margin-bottom: 0in">1. Plain (non-layered) +execution chain is simple and efficient. The main idea is to minimize +scheduling overhead by Scheduler going through the chain. Each +priority layer adds scheduling overhead to overall task chain +execution. Let’s review 3 scenarios:</P> +<P CLASS="western" STYLE="margin-left: 0.49in; margin-bottom: 0in"><BR> +</P> +<P CLASS="western" STYLE="margin-left: 0.49in; margin-bottom: 0in"><B>I. +Flat chain of 7 tasks:</B></P> +<P CLASS="western" STYLE="margin-left: 0.49in; margin-bottom: 0in">Scheduling +evaluation sequence:</P> +<P CLASS="western" ALIGN=CENTER STYLE="margin-left: 0.49in; margin-bottom: 0in"> +1 <FONT FACE="Wingdings"></FONT> 2 <FONT FACE="Wingdings"></FONT> +3 <FONT FACE="Wingdings"></FONT> 4 <FONT FACE="Wingdings"></FONT> +5 <FONT FACE="Wingdings"></FONT> 6 <FONT FACE="Wingdings"></FONT> +7</P> +<P CLASS="western" ALIGN=CENTER STYLE="margin-left: 0.49in; margin-bottom: 0in"> +<BR> +</P> +<P CLASS="western" STYLE="margin-left: 0.49in; margin-bottom: 0in">Scheduling +overhead:</P> +<P CLASS="western" STYLE="margin-left: 0.49in; margin-bottom: 0in">O += B * T = 7 * 18 = 126 microseconds,</P> +<P CLASS="western" STYLE="margin-left: 0.49in; margin-bottom: 0in">Where:</P> +<P CLASS="western" STYLE="margin-left: 0.98in; margin-bottom: 0in">O +– scheduling overhead</P> +<P CLASS="western" STYLE="margin-left: 0.98in; margin-bottom: 0in">B +– number of tasks in the base layer</P> +<P CLASS="western" STYLE="margin-left: 0.98in; margin-bottom: 0in">T +– scheduling overhead of a single task execution evaluation +(currently with Arduino Uno running at 16 Mhz is between 15 and 18 +microseconds).</P> +<P CLASS="western" STYLE="margin-bottom: 0in"><BR> +</P> +<P CLASS="western" STYLE="margin-left: 0.49in; margin-bottom: 0in"><B>II. +Two priority layers of 7 tasks. </B> +</P> +<P CLASS="western" STYLE="margin-left: 0.49in; margin-bottom: 0in"><B> </B>Tasks +1, 2, 3, 4, 5 are base priority and 6, 7 are higher priority:</P> +<P CLASS="western" STYLE="margin-left: 0.49in; margin-bottom: 0in"><BR> +</P> +<P CLASS="western" STYLE="margin-left: 0.49in; margin-bottom: 0in">Scheduling +evaluation sequence:</P> +<P CLASS="western" ALIGN=CENTER STYLE="margin-left: 0.49in; margin-bottom: 0in"> +6 <FONT FACE="Wingdings"></FONT> 7 <FONT FACE="Wingdings"></FONT> +1 <FONT FACE="Wingdings"></FONT> 6 <FONT FACE="Wingdings"></FONT> +7 <FONT FACE="Wingdings"></FONT> 2 <FONT FACE="Wingdings"></FONT> +6 <FONT FACE="Wingdings"></FONT> 7 <FONT FACE="Wingdings"></FONT> +3 <FONT FACE="Wingdings"></FONT> 6 <FONT FACE="Wingdings"></FONT> +7 <FONT FACE="Wingdings"></FONT> 4 <FONT FACE="Wingdings"></FONT> +6 <FONT FACE="Wingdings"></FONT> 7 <FONT FACE="Wingdings"></FONT> +5</P> +<P CLASS="western" ALIGN=CENTER STYLE="margin-left: 0.49in; margin-bottom: 0in"> +<BR> +</P> +<P CLASS="western" STYLE="margin-left: 0.49in; margin-bottom: 0in">Scheduling +overhead:</P> +<P CLASS="western" STYLE="margin-left: 0.49in; margin-bottom: 0in">O += (B + B * P1) * T = (5 + 5 * 2) * 18 = 270 microseconds,</P> +<P CLASS="western" STYLE="margin-left: 0.49in; margin-bottom: 0in">Where:</P> +<P CLASS="western" STYLE="margin-left: 0.98in; margin-bottom: 0in">O +– scheduling overhead</P> +<P CLASS="western" STYLE="margin-left: 0.98in; margin-bottom: 0in">B +– number of tasks in the base layer</P> +<P CLASS="western" STYLE="margin-left: 0.98in; margin-bottom: 0in">P1 +– number of tasks in the priority 1 layer</P> +<P CLASS="western" STYLE="margin-left: 0.98in; margin-bottom: 0in">T +– scheduling overhead of a single task execution evaluation +(currently with Arduino Uno running at 16 Mhz is between 15 and 18 +microseconds).</P> +<P CLASS="western" STYLE="margin-bottom: 0in"><BR> +</P> +<P CLASS="western" STYLE="margin-left: 0.49in; margin-bottom: 0in"><B>III. +Three priority layers of 7 tasks. </B> +</P> +<P CLASS="western" STYLE="margin-left: 0.49in; margin-bottom: 0in"><B> </B>Tasks +1, 2, 3, are base priority, 4, 5 are priority 1, and 6, 7 are +priority 2:</P> +<P CLASS="western" STYLE="margin-left: 0.49in; margin-bottom: 0in"><BR> +</P> +<P CLASS="western" STYLE="margin-left: 0.49in; margin-bottom: 0in">Scheduling +evaluation sequence:</P> +<P CLASS="western" ALIGN=CENTER STYLE="margin-left: 0.49in; margin-bottom: 0in"> +6 <FONT FACE="Wingdings"></FONT> 7 <FONT FACE="Wingdings"></FONT> +4 <FONT FACE="Wingdings"></FONT> 6 <FONT FACE="Wingdings"></FONT> +7 <FONT FACE="Wingdings"></FONT> 5 <FONT FACE="Wingdings"></FONT> +1 <FONT FACE="Wingdings"></FONT> 6 <FONT FACE="Wingdings"></FONT> +7 <FONT FACE="Wingdings"></FONT> 4 <FONT FACE="Wingdings"></FONT> +6 <FONT FACE="Wingdings"></FONT> 7 <FONT FACE="Wingdings"></FONT> +5 <FONT FACE="Wingdings"></FONT> 2 <FONT FACE="Wingdings"></FONT>6 +<FONT FACE="Wingdings"></FONT> 7 <FONT FACE="Wingdings"></FONT> +4 <FONT FACE="Wingdings"></FONT> 6 <FONT FACE="Wingdings"></FONT> +7 <FONT FACE="Wingdings"></FONT> 5 <FONT FACE="Wingdings"></FONT> +3 +</P> +<P CLASS="western" ALIGN=CENTER STYLE="margin-left: 0.49in; margin-bottom: 0in"> +<BR> +</P> +<P CLASS="western" STYLE="margin-left: 0.49in; margin-bottom: 0in">Scheduling +overhead:</P> +<P CLASS="western" STYLE="margin-left: 0.49in; margin-bottom: 0in">O += (B + B * P1 + B * P1 * P2) * T = (3 + 3 * 2 + 3 * 2 * 2) * 18 = 378 +microseconds,</P> +<P CLASS="western" STYLE="margin-left: 0.49in; margin-bottom: 0in">Where:</P> +<P CLASS="western" STYLE="margin-left: 0.98in; margin-bottom: 0in">O +– scheduling overhead</P> +<P CLASS="western" STYLE="margin-left: 0.98in; margin-bottom: 0in">B +– number of tasks in the base layer</P> +<P CLASS="western" STYLE="margin-left: 0.98in; margin-bottom: 0in">P1 +– number of tasks in the priority 1 layer</P> +<P CLASS="western" STYLE="margin-left: 0.98in; margin-bottom: 0in">P2 +– number of tasks in the priority 2 layer</P> +<P CLASS="western" STYLE="margin-left: 0.98in; margin-bottom: 0in">T +– scheduling overhead of a single task execution evaluation +(currently with Arduino Uno running at 16 Mhz is between 15 and 18 +microseconds).</P> +<P CLASS="western" STYLE="margin-bottom: 0in"><BR> +</P> +<P CLASS="western" STYLE="margin-bottom: 0in">Scheduling overhead of +a 3 layer prioritization approach is 3 times higher than that of a +flat execution chain. <B>Do</B> evaluate if task prioritization is +really required for your sketch.</P> <P CLASS="western" STYLE="margin-bottom: 0in"><BR> </P> <P CLASS="western" STYLE="margin-bottom: 0in"><BR> @@ -338,7 +493,7 @@ cooperative behavior.</P> significant benefits: you don't need to worry about concurrency inside the callback method, since only one callback method runs at a time, and could not be interrupted. All resources are yours for that -period of time, noone can switch the value of variables (except +period of time, no one can switch the value of variables (except interrupt functions of course...), etc. It is a stable and predictable environment, and it helps a lot with writing stable code. </P> @@ -426,7 +581,7 @@ callback methods written for cooperative multitasking.</P> <P CLASS="western" STYLE="margin-bottom: 0in"><BR> </P> <P CLASS="western" STYLE="margin-left: 0.49in; margin-bottom: 0in">a) -<B>DO NOT</B> use Arduino's <FONT FACE="FreeMono, MS Mincho, monospace"><FONT SIZE=2 STYLE="font-size: 10pt">delay()</FONT></FONT><FONT FACE="Andale Mono, MS Mincho"> +<B>DO NOT</B> use Arduino's <FONT FACE="FreeMono, MS Mincho, monospace"><FONT SIZE=2 STYLE="font-size: 10pt"><B>delay</B></FONT></FONT><FONT FACE="FreeMono, MS Mincho, monospace"><FONT SIZE=2 STYLE="font-size: 10pt">()</FONT></FONT><FONT FACE="Andale Mono, MS Mincho"> </FONT>function. It is blocking and will hold the entire chain. Instead break the callback method into two, switch the callback method of the task where delay is necessary and delay the task by @@ -533,7 +688,7 @@ more stuff</FONT></FONT></P> <P CLASS="western" STYLE="margin-left: 0.49in; margin-bottom: 0in"><BR> </P> <P CLASS="western" STYLE="margin-left: 0.49in; margin-bottom: 0in">b) -Same goes to <FONT FACE="FreeMono, MS Mincho, monospace"><FONT SIZE=2 STYLE="font-size: 10pt">pulseIn()</FONT></FONT> +Same goes to <FONT FACE="FreeMono, MS Mincho, monospace"><FONT SIZE=2 STYLE="font-size: 10pt"><B>pulseIn</B></FONT></FONT><FONT FACE="FreeMono, MS Mincho, monospace"><FONT SIZE=2 STYLE="font-size: 10pt">()</FONT></FONT> function. If you have to use it, set the timeout parameter such that it is not a default 1 second. PulseIn functionality could be achieved via pin interrupts, and that solution is non-blocking.</P> @@ -711,7 +866,7 @@ stuff // one loop action</FONT></FONT></P> </P> <P CLASS="western" STYLE="margin-left: 0.49in; margin-bottom: 0in">d) Break long running callback methods into several shorter ones, and -pass control from one to the other via <FONT FACE="FreeMono, MS Mincho, monospace"><FONT SIZE=2 STYLE="font-size: 10pt">setCallback() +pass control from one to the other via <FONT FACE="FreeMono, MS Mincho, monospace"><FONT SIZE=2 STYLE="font-size: 10pt"><B>setCallback</B></FONT></FONT><FONT FACE="FreeMono, MS Mincho, monospace"><FONT SIZE=2 STYLE="font-size: 10pt">() </FONT></FONT>method:</P> <P CLASS="western" STYLE="margin-left: 0.49in; margin-bottom: 0in"><BR> </P> @@ -792,11 +947,11 @@ do last part of the stuff</FONT></FONT></P> <P CLASS="western" STYLE="margin-left: 0.49in; margin-bottom: 0in"><BR> </P> <P CLASS="western" STYLE="margin-left: 0.49in; margin-bottom: 0in">This -will execute all parts of the callback function in three successive -steps, sheduled immediately, but allowing other tasks in the chain to -run. Notice that task is scheduled to run immediately, and 1 second -period is achieved by delaying the task for 1000 millis at the last -step. +will execute all parts of the callback function in three successive +steps, scheduled immediately, but allowing other tasks in the chain +to run. Notice that task is scheduled to run immediately, and 1 +second period is achieved by delaying the task for 1000 millis at the +last step. </P> <P CLASS="western" STYLE="margin-left: 0.49in; margin-bottom: 0in"><BR> </P> @@ -1034,12 +1189,12 @@ getIterations() </B> </P> <P CLASS="western" STYLE="margin-left: 0.49in; margin-bottom: 0in"><BR> </P> -<P CLASS="western" STYLE="margin-bottom: 0in"><B>long getOverrun()</B></P> -<P CLASS="western" STYLE="margin-left: 0.49in; margin-bottom: 0in; font-weight: normal"> -If library is compiled with <FONT FACE="Courier New, monospace">_TASK_TIMECRITICAL</FONT> +<P CLASS="western" STYLE="margin-bottom: 0in"><B>long getStartDelay()</B></P> +<P CLASS="western" STYLE="margin-left: 0.49in; margin-bottom: 0in">If +library is compiled with <FONT FACE="Courier New, monospace">_TASK_TIMECRITICAL</FONT> enabled, you can assess how much later the callback method was invoked against when it was scheduled to be invoked. The return value -of <B>getOverrun() </B>method provides this information in +of <B>getStartDelay () </B>method provides this information in milliseconds. </P> <P CLASS="western" STYLE="margin-bottom: 0in"><BR> @@ -1391,6 +1546,8 @@ a StatusReqeust object this Task was waiting on. </P> <P CLASS="western" STYLE="margin-left: 0.49in; margin-bottom: 0in"><BR> </P> +<P CLASS="western" STYLE="margin-left: 0.49in; margin-bottom: 0in"><BR> +</P> <P CLASS="western" STYLE="margin-bottom: 0in; page-break-after: avoid"> <B>TASK ID, CONTROL POINTS METHODS:</B></P> <P CLASS="western" STYLE="margin-bottom: 0in; page-break-after: avoid"> @@ -1477,6 +1634,95 @@ implementation options. </P> <P CLASS="western" STYLE="margin-left: 0.49in; margin-bottom: 0in"><BR> </P> +<P CLASS="western" STYLE="margin-left: 0.49in; margin-bottom: 0in"><BR> +</P> +<P CLASS="western" STYLE="margin-left: 0.49in; margin-bottom: 0in"><BR> +</P> +<P CLASS="western" STYLE="margin-bottom: 0in; page-break-after: avoid"> +<B>STATUS REQUEST:</B></P> +<P CLASS="western" STYLE="margin-bottom: 0in; page-break-after: avoid"> +<BR> +</P> +<P CLASS="western" STYLE="margin-bottom: 0in; page-break-after: avoid"> +<B>CREATION:</B></P> +<P CLASS="western" STYLE="margin-bottom: 0in; page-break-after: avoid"> +<BR> +</P> +<P CLASS="western" STYLE="margin-bottom: 0in"><B>StatusRequest()</B><BR><BR> +</P> +<P CLASS="western" STYLE="margin-left: 0.49in; margin-bottom: 0in">Default +constructor. +</P> +<P CLASS="western" STYLE="margin-left: 0.49in; margin-bottom: 0in">Takes +no parameters. Creates Status Request object, which is assigned a +status of “completed” on creation. +</P> +<P CLASS="western" STYLE="margin-left: 0.49in; margin-bottom: 0in"><BR> +</P> +<P CLASS="western" STYLE="margin-bottom: 0in"><B>void +setWaiting(unsigned int aCount = 1)</B></P> +<P CLASS="western" STYLE="margin-left: 0.49in; margin-bottom: 0in">Activates +Status Request object. By default each object is set to wait on one +event only, however, if <B>aCount</B> is supplied, Status Request can +wait on multiple events. For instance, <B>setWaiting(3)</B> will wait +on three signals. An example could be waiting for completion of +measurements from 3 sensors. +</P> +<P CLASS="western" STYLE="margin-left: 0.49in; margin-bottom: 0in"><BR> +</P> +<P CLASS="western" STYLE="margin-bottom: 0in"><B>bool signal(int +aStatus)</B></P> +<P CLASS="western" STYLE="margin-left: 0.49in; margin-bottom: 0in">Signals +completion of the event to the Status Request object, and passes a +completion code, which could be interrogated later. +</P> +<P CLASS="western" STYLE="margin-left: 0.49in; margin-bottom: 0in"><B>Note: +</B> passing a <B>negative</B> status code to the status request +object is considered reporting an error condition, and will complete +the status request regardless of how many outstanding signals it is +still waiting for. +</P> +<P CLASS="western" STYLE="margin-left: 0.49in; margin-bottom: 0in"><B>Note</B>: +only the latest status code is kept.</P> +<P CLASS="western" STYLE="margin-left: 0.49in; margin-bottom: 0in"><BR> +</P> +<P CLASS="western" STYLE="margin-bottom: 0in"><B>bool signalComplete +(int aStatus)</B></P> +<P CLASS="western" STYLE="margin-left: 0.49in; margin-bottom: 0in">Signals +completion of <B>ALL</B> events to the Status Request object, and +passes a completion code, which could be interrogated later. The +status request completes regardless of how many events it is still +waiting on. +</P> +<P CLASS="western" STYLE="margin-left: 0.49in; margin-bottom: 0in"><BR> +</P> +<P CLASS="western" STYLE="margin-bottom: 0in"><B>bool pending() </B> +</P> +<P CLASS="western" STYLE="margin-left: 0.49in; margin-bottom: 0in">Returns +<B>true</B> if status request is still waiting for event or events to +happen.</P> +<P CLASS="western" STYLE="margin-left: 0.49in; margin-bottom: 0in"><BR> +</P> +<P CLASS="western" STYLE="margin-bottom: 0in"><B>bool completed () </B> +</P> +<P CLASS="western" STYLE="margin-left: 0.49in; margin-bottom: 0in">Returns +<B>true</B> if status has completed.</P> +<P CLASS="western" STYLE="margin-left: 0.49in; margin-bottom: 0in"><BR> +</P> +<P CLASS="western" STYLE="margin-bottom: 0in"><B>int getStatus()</B></P> +<P CLASS="western" STYLE="margin-left: 0.49in; margin-bottom: 0in">Returns +the status code passed to the status request object by the <B>signal() +</B>and <B>signalComplete() </B>methods. +</P> +<P CLASS="western" STYLE="margin-left: 0.49in; margin-bottom: 0in">Any +<B>positive</B> number is considered a successful completion status.</P> +<P CLASS="western" STYLE="margin-left: 0.49in; margin-bottom: 0in">A +0 (zero) is considered a default successful completion status.</P> +<P CLASS="western" STYLE="margin-left: 0.49in; margin-bottom: 0in">Any +<B>negative</B> number is considered an error code and unsuccessful +completion of a request.</P> +<P CLASS="western" STYLE="margin-bottom: 0in"><BR> +</P> <P CLASS="western" STYLE="margin-bottom: 0in"><BR> </P> <P CLASS="western" STYLE="margin-bottom: 0in; page-break-after: avoid"> @@ -1571,8 +1817,10 @@ in case not tasks are scheduled to run.</P> <B>default</B> behavior of scheduler upon creation is to allow sleep mode. </P> -<P CLASS="western" STYLE="margin-bottom: 0in"><BR><B>void enableAll()</B></P> -<P CLASS="western" STYLE="margin-bottom: 0in"><B>void disableAll()</B></P> +<P CLASS="western" STYLE="margin-bottom: 0in"><BR><B>void +enableAll(bool aRecursive= true)</B></P> +<P CLASS="western" STYLE="margin-bottom: 0in"><B>void disableAll(bool +aRecursive= true)</B></P> <P CLASS="western" STYLE="margin-bottom: 0in"><BR> </P> <P CLASS="western" STYLE="margin-left: 0.49in; margin-bottom: 0in">enables @@ -1580,6 +1828,11 @@ and disables (respectively) all tasks in the chain. Convenient if your need to enable/disable majority of the tasks (i.e. disable all and then enable one). </P> +<P CLASS="western" STYLE="margin-left: 0.49in; margin-bottom: 0in">If +support for layered task priority is enabled, supplying <B>aRecursive</B> +parameter will enable/disable higher priority tasks as well (<B>true</B>, +default), or tasks only on this priority layer (<B>false</B>). +</P> <P CLASS="western" STYLE="margin-bottom: 0in; page-break-after: avoid"> <BR><B>Task& currentTask()<BR></B><BR> </P> @@ -1606,21 +1859,34 @@ pointer to Local Task Storage of the task, currently executing via <B>execute()</B> loop <B>OR </B>for OnEnable and OnDisable methods, task being enabled or disabled. </P> -<P CLASS="western" STYLE="margin-bottom: 0in"><BR><B>void execute()</B></P> +<P CLASS="western" STYLE="margin-bottom: 0in"><BR><B>bool execute()</B></P> <P CLASS="western" STYLE="margin-bottom: 0in"><BR> </P> <P CLASS="western" STYLE="margin-left: 0.49in; margin-bottom: 0in">Executes -one scheduling pass, including end-of-pass sleep. This method is -typically placed inside the <B>loop()</B> method of the sketch. Since -<B>execute</B> exits after every pass, you can put additional -statements after <B>execute</B> inside the <B>loop().</B></P> +one scheduling pass, including (in case of the base priority +scheduler) end-of-pass sleep. This method is typically placed inside +the <B>loop()</B> method of the sketch. Since <B>execute</B> exits +after every pass, you can put additional statements after <B>execute</B> +inside the <B>loop().</B></P> +<P CLASS="western" STYLE="margin-left: 0.49in; margin-bottom: 0in"><BR> +</P> +<P CLASS="western" STYLE="margin-left: 0.49in; margin-bottom: 0in"><B>If +layered task prioritization is enabled, all higher priority tasks +will be evaluated and invoked by the base <FONT FACE="Courier New, monospace">execute()</FONT> +method. There is no need to call <FONT FACE="Courier New, monospace">execute()</FONT> +of the higher priority schedulers explicitly. </B> +</P> +<P CLASS="western" STYLE="margin-left: 0.49in; margin-bottom: 0in"><BR> +</P> <P CLASS="western" STYLE="margin-left: 0.49in; margin-bottom: 0in">Generally, -execute will perform the following steps:</P> +base priority execute will perform the following steps:</P> <OL> + <LI><P CLASS="western" STYLE="margin-bottom: 0in">Call higher + priority scheduler’s execute method, if provided.</P> <LI><P CLASS="western" STYLE="margin-bottom: 0in">Ignore task completely if it is disabled.</P> <LI><P CLASS="western" STYLE="margin-bottom: 0in">Disable task if it - ran out of iterations (calling OnDesable, if necessary).</P> + ran out of iterations (calling OnDisable, if necessary).</P> <LI><P CLASS="western" STYLE="margin-bottom: 0in">Check if task is waiting on a StatusRequest object, and make appropriate scheduling arrangements</P> @@ -1650,100 +1916,54 @@ has overrun its scheduled start time when it was invoked. Returns <B>false</B> if task has been invoked according to schedule.</P> <P CLASS="western" STYLE="margin-left: 0.49in; margin-bottom: 0in"><BR> </P> -<P CLASS="western" STYLE="margin-left: 0.49in; margin-bottom: 0in"><BR> -</P> -<P CLASS="western" STYLE="margin-bottom: 0in; page-break-after: avoid"> -<B>STATUS REQUEST:</B></P> <P CLASS="western" STYLE="margin-bottom: 0in; page-break-after: avoid"> <BR> </P> <P CLASS="western" STYLE="margin-bottom: 0in; page-break-after: avoid"> -<B>CREATION:</B></P> +<B>TASK PRIORITY:</B></P> <P CLASS="western" STYLE="margin-bottom: 0in; page-break-after: avoid"> <BR> </P> -<P CLASS="western" STYLE="margin-bottom: 0in"><B>StatusRequest()</B><BR><BR> -</P> -<P CLASS="western" STYLE="margin-left: 0.49in; margin-bottom: 0in">Default -constructor. -</P> -<P CLASS="western" STYLE="margin-left: 0.49in; margin-bottom: 0in">Takes -no parameters. Creates Status Request object, which is assigned a -status of “completed” on creation. -</P> -<P CLASS="western" STYLE="margin-left: 0.49in; margin-bottom: 0in"><BR> -</P> <P CLASS="western" STYLE="margin-bottom: 0in"><B>void -setWaiting(unsigned int aCount = 1)</B></P> -<P CLASS="western" STYLE="margin-left: 0.49in; margin-bottom: 0in">Activates -Status Request object. By default each object is set to wait on one -event only, however, if <B>aCount</B> is supplied, Status Request can -wait on multiple events. For instance, <B>setWaiting(3)</B> will wait -on three signals. An example could be waiting for completion of -measurements from 3 sensors. -</P> -<P CLASS="western" STYLE="margin-left: 0.49in; margin-bottom: 0in"><BR> -</P> -<P CLASS="western" STYLE="margin-bottom: 0in"><B>bool signal(int -aStatus)</B></P> -<P CLASS="western" STYLE="margin-left: 0.49in; margin-bottom: 0in">Signals -completion of the event to the Status Request object, and passes a -completion code, which could be interrogated later. -</P> -<P CLASS="western" STYLE="margin-left: 0.49in; margin-bottom: 0in"><B>Note: -</B> passing a <B>negative</B> status code to the status request -object is considered reporting an error condition, and will complete -the status request regardless of how many outstanding signals it is -still waiting for. -</P> -<P CLASS="western" STYLE="margin-left: 0.49in; margin-bottom: 0in"><B>Note</B>: -only the latest status code is kept.</P> -<P CLASS="western" STYLE="margin-left: 0.49in; margin-bottom: 0in"><BR> -</P> -<P CLASS="western" STYLE="margin-bottom: 0in"><B>bool signalComplete -(int aStatus)</B></P> -<P CLASS="western" STYLE="margin-left: 0.49in; margin-bottom: 0in">Signals -completion of <B>ALL</B> events to the Status Request object, and -passes a completion code, which could be interrogated later. The -status request completes regardless of how many events it is still -waiting on. +setHighPriorityScheduler(Scheduler* aScheduler);</B><BR><BR> </P> -<P CLASS="western" STYLE="margin-left: 0.49in; margin-bottom: 0in"><BR> -</P> -<P CLASS="western" STYLE="margin-bottom: 0in"><B>bool pending() </B> +<P CLASS="western" STYLE="margin-left: 0.49in; margin-bottom: 0in">If +library is compiled with <FONT FACE="Courier New, monospace">_TASK_PRIORITY +</FONT>enabled, this method associates current scheduler with a +higher priority scheduler. </P> -<P CLASS="western" STYLE="margin-left: 0.49in; margin-bottom: 0in">Returns -<B>true</B> if status request is still waiting for event or events to -happen.</P> +<P CLASS="western" STYLE="margin-left: 0.49in; margin-bottom: 0in"><B>NOTE: +</B>Only one <B>execute() </B>method needs to be explicitly called in +the main <B>loop(). </B>That is the execute method of <B>base</B> +priority scheduler. All higher priority schedulers are called by the +base priority scheduler.</P> <P CLASS="western" STYLE="margin-left: 0.49in; margin-bottom: 0in"><BR> </P> -<P CLASS="western" STYLE="margin-bottom: 0in"><B>bool completed () </B> +<P CLASS="western" STYLE="margin-bottom: 0in"><B>static Scheduler& +currentScheduler()</B></P> +<P CLASS="western" STYLE="margin-left: 0.49in; margin-bottom: 0in">If +library is compiled with <FONT FACE="Courier New, monospace">_TASK_PRIORITY +</FONT>enabled, this method returns reference to a scheduler, which +invoked current task. </P> -<P CLASS="western" STYLE="margin-left: 0.49in; margin-bottom: 0in">Returns -<B>true</B> if status has completed.</P> <P CLASS="western" STYLE="margin-left: 0.49in; margin-bottom: 0in"><BR> </P> -<P CLASS="western" STYLE="margin-bottom: 0in"><B>int getStatus()</B></P> -<P CLASS="western" STYLE="margin-left: 0.49in; margin-bottom: 0in">Returns -the status code passed to the status request object by the <B>signal() -</B>and <B>signalComplete() </B>methods. -</P> -<P CLASS="western" STYLE="margin-left: 0.49in; margin-bottom: 0in">Any -<B>positive</B> number is considered a successful completion status.</P> -<P CLASS="western" STYLE="margin-left: 0.49in; margin-bottom: 0in">A -0 (zero) is considered a default successful completion status.</P> -<P CLASS="western" STYLE="margin-left: 0.49in; margin-bottom: 0in">Any -<B>negative</B> number is considered an error code and unsuccessful -completion of a request.</P> -<P CLASS="western" STYLE="margin-left: 0.49in; margin-bottom: 0in"><BR> +<P CLASS="western" STYLE="margin-left: 0.49in; margin-bottom: 0in"><B>NOTE: +Please refer to examples 11 and 12 for illustration of Task Priority +functionality</B></P> +<P CLASS="western" STYLE="margin-bottom: 0in; page-break-after: avoid"> +<BR> </P> -<P CLASS="western" STYLE="margin-left: 0.49in; margin-bottom: 0in"><BR> +<P CLASS="western" STYLE="margin-bottom: 0in; page-break-after: avoid"> +<BR> </P> -<P CLASS="western" STYLE="margin-left: 0.49in; margin-bottom: 0in"><BR> +<P CLASS="western" STYLE="margin-bottom: 0in; page-break-after: avoid"> +<BR> </P> <P CLASS="western" STYLE="margin-bottom: 0in; page-break-after: avoid"> <B>CONSTANTS:</B></P> -<P CLASS="western" STYLE="margin-bottom: 0in"><BR> +<P CLASS="western" STYLE="margin-bottom: 0in; page-break-after: avoid"> +<BR> </P> <P CLASS="western" STYLE="margin-left: 0.49in; margin-bottom: 0in; page-break-after: avoid"> <B>TASK_SECOND (1000)</B></P> @@ -1783,13 +2003,15 @@ interval for immediate execution</P> </P> <P CLASS="western" STYLE="margin-bottom: 0in; page-break-before: always; page-break-after: avoid"> <B>IMPLEMENTATION SCENARIOS AND IDEAS:</B></P> -<P CLASS="western" STYLE="margin-bottom: 0in"><BR> +<P CLASS="western" STYLE="margin-bottom: 0in; page-break-after: avoid"> +<BR> </P> <OL> - <LI><P CLASS="western" STYLE="margin-bottom: 0in"><B>EVENT DRIVEN - PROGRAMMING</B></P> + <LI><P CLASS="western" STYLE="margin-bottom: 0in; page-break-after: avoid"> + <B>EVENT DRIVEN PROGRAMMING</B></P> </OL> -<P CLASS="western" STYLE="margin-bottom: 0in"><BR> +<P CLASS="western" STYLE="margin-bottom: 0in; page-break-after: avoid"> +<BR> </P> <P CLASS="western" STYLE="margin-bottom: 0in">Each of the processes of your application becomes a separate and distinct programming area, @@ -1876,10 +2098,12 @@ measureHumidity();<BR>}<BR><BR><BR>void loop ()<BR>{<BR> taskManager.execute();<BR>}</FONT><FONT FACE="Times New Roman, serif"><BR></FONT></FONT><BR> </P> <OL START=2> - <LI><P CLASS="western" STYLE="margin-bottom: 0in">“<FONT FACE="Times New Roman, serif"><B>NATIVE” - SUPPORT FOR FINITE STATE MACHINE</B></FONT></P> + <LI><P CLASS="western" STYLE="margin-bottom: 0in; page-break-after: avoid"> + “<FONT FACE="Times New Roman, serif"><B>NATIVE” SUPPORT FOR + FINITE STATE MACHINE</B></FONT></P> </OL> -<P CLASS="western" STYLE="margin-bottom: 0in"><BR> +<P CLASS="western" STYLE="margin-bottom: 0in; page-break-after: avoid"> +<BR> </P> <P CLASS="western" STYLE="margin-bottom: 0in"><FONT FACE="Times New Roman, serif">Define “states” as callback method or methods. Each callback method @@ -1942,10 +2166,12 @@ used to go through states.</FONT></P> <P CLASS="western" STYLE="margin-bottom: 0in"><BR> </P> <OL START=3> - <LI><P CLASS="western" STYLE="margin-bottom: 0in"><FONT FACE="Times New Roman, serif"><B>MULTIPLE - POSSIBLE CALLBACKS FOR TASK</B></FONT></P> + <LI><P CLASS="western" STYLE="margin-bottom: 0in; page-break-after: avoid"> + <FONT FACE="Times New Roman, serif"><B>MULTIPLE POSSIBLE CALLBACKS + FOR TASK</B></FONT></P> </OL> -<P CLASS="western" STYLE="margin-bottom: 0in"><BR> +<P CLASS="western" STYLE="margin-bottom: 0in; page-break-after: avoid"> +<BR> </P> <P CLASS="western" STYLE="margin-bottom: 0in"><FONT FACE="Times New Roman, serif">There may be a need to select an option for callback method based on @@ -2024,11 +2250,13 @@ pass. </FONT> <P CLASS="western" STYLE="margin-bottom: 0in"><BR> </P> <OL START=3> - <LI><P CLASS="western" STYLE="margin-bottom: 0in"><FONT FACE="Times New Roman, serif"><B>INTERRUP-DRIVEN - EXECUTION SUPPORT </B></FONT> + <LI><P CLASS="western" STYLE="margin-bottom: 0in; page-break-after: avoid"> + <FONT FACE="Times New Roman, serif"><B>INTERRUP-DRIVEN EXECUTION + SUPPORT </B></FONT> </P> </OL> -<P CLASS="western" STYLE="margin-bottom: 0in"><BR> +<P CLASS="western" STYLE="margin-bottom: 0in; page-break-after: avoid"> +<BR> </P> <P CLASS="western" STYLE="margin-bottom: 0in"><FONT FACE="Times New Roman, serif">In case of interrupt-driven program flow, tasks could be scheduled to @@ -2112,11 +2340,13 @@ LOW;<BR> <BR>}<BR><BR>void loop() {<BR> // put your main code here, to run repeatedly:<BR> r.execute();<BR>}<BR></FONT></FONT><BR> </P> <OL START=3> - <LI><P CLASS="western" STYLE="margin-bottom: 0in"><FONT FACE="Times New Roman, serif"><B>USING - ONENABLE AND ONDISBALE METHODS </B></FONT> + <LI><P CLASS="western" STYLE="margin-bottom: 0in; page-break-after: avoid"> + <FONT FACE="Times New Roman, serif"><B>USING ONENABLE AND ONDISBALE + METHODS </B></FONT> </P> </OL> -<P CLASS="western" STYLE="margin-bottom: 0in"><BR> +<P CLASS="western" STYLE="margin-bottom: 0in; page-break-after: avoid"> +<BR> </P> <P CLASS="western" STYLE="margin-left: 0.49in; margin-bottom: 0in"><FONT FACE="Times New Roman, serif">Consider a task to flash onboard LED for 5 seconds with random frequency. Task @@ -2301,11 +2531,13 @@ code here, to run repeatedly:</FONT></FONT></P> <P CLASS="western" STYLE="margin-left: 0.49in; margin-bottom: 0in"><BR> </P> <OL START=3> - <LI><P CLASS="western" STYLE="margin-bottom: 0in"><FONT FACE="Times New Roman, serif"><B>USING - STATUS REQUEST OBJECTS </B></FONT> + <LI><P CLASS="western" STYLE="margin-bottom: 0in; page-break-after: avoid"> + <FONT FACE="Times New Roman, serif"><B>USING STATUS REQUEST OBJECTS + </B></FONT> </P> </OL> -<P CLASS="western" STYLE="margin-left: 0.49in; margin-bottom: 0in"><BR> +<P CLASS="western" STYLE="margin-left: 0.49in; margin-bottom: 0in; page-break-after: avoid"> +<BR> </P> <P CLASS="western" STYLE="margin-left: 0.49in; margin-bottom: 0in"><FONT FACE="Times New Roman, serif"><FONT SIZE=2 STYLE="font-size: 11pt">This test emulates querying 3 sensors once every 10 seconds, each could @@ -2683,11 +2915,13 @@ loop() {</FONT></FONT></P> <P CLASS="western" STYLE="margin-left: 0.49in; margin-bottom: 0in"><BR> </P> <OL START=3> - <LI><P CLASS="western" STYLE="margin-bottom: 0in"><FONT FACE="Times New Roman, serif"><B>USING - LOCAL TASK STORAGE POINTER </B></FONT> + <LI><P CLASS="western" STYLE="margin-bottom: 0in; page-break-after: avoid"> + <FONT FACE="Times New Roman, serif"><B>USING LOCAL TASK STORAGE + POINTER </B></FONT> </P> </OL> -<P CLASS="western" STYLE="margin-left: 0.49in; margin-bottom: 0in"><BR> +<P CLASS="western" STYLE="margin-left: 0.49in; margin-bottom: 0in; page-break-after: avoid"> +<BR> </P> <P CLASS="western" STYLE="margin-left: 0.49in; margin-bottom: 0in"><FONT FACE="Times New Roman, serif"><FONT SIZE=2 STYLE="font-size: 11pt">Tasks can store a pointer to specific variable, structure or array, which @@ -2798,6 +3032,83 @@ V1 = *((sensor_data*) ts.currentLts());</FONT></FONT></P> <P CLASS="western" STYLE="margin-left: 0.49in; margin-bottom: 0in"><BR> </P> <OL START=3> + <LI><P CLASS="western" STYLE="margin-bottom: 0in; page-break-after: avoid"> + <FONT FACE="Times New Roman, serif"><B>ENABLING TASK PRIORITIZATION + </B></FONT> + </P> +</OL> +<P CLASS="western" STYLE="margin-left: 0.49in; margin-bottom: 0in; page-break-after: avoid"> +<BR> +</P> +<P CLASS="western" STYLE="margin-left: 0.49in; margin-bottom: 0in"><FONT FACE="Times New Roman, serif"><FONT SIZE=2 STYLE="font-size: 11pt">In +certain cases you want a task to be invoked before others in case of +scheduling collision (tasks ready to be invoked at the same time). In +a flat execution chain scenario tasks are evaluated for execution in +the order they were added to the chain. Therefore a single task has +to wait for the rest of the chain to be evaluated to get a chance +again. </FONT></FONT> +</P> +<P CLASS="western" STYLE="margin-left: 0.49in; margin-bottom: 0in"><FONT FACE="Times New Roman, serif"><FONT SIZE=2 STYLE="font-size: 11pt">Consider +a scenario where a task taking gyroscope measurements has to be +invoked as close to the actual scheduling time as possible. That is +when task prioritization comes to help. </FONT></FONT> +</P> +<P CLASS="western" STYLE="margin-left: 0.49in; margin-bottom: 0in"><FONT FACE="Times New Roman, serif"><FONT SIZE=2 STYLE="font-size: 11pt">Let’s +say tasks t4 and t5 are taking measurements from gyroscope and +accelerometer, and tasks t1, t2 and t3 are doing something less +important.</FONT></FONT></P> +<P CLASS="western" STYLE="margin-left: 0.49in; margin-bottom: 0in"><FONT FACE="Times New Roman, serif"><FONT SIZE=2 STYLE="font-size: 11pt">This +is how such setup is coded:</FONT></FONT></P> +<P CLASS="western" STYLE="margin-left: 0.49in; margin-bottom: 0in"><BR> +</P> +<P CLASS="western" STYLE="margin-left: 0.98in; margin-bottom: 0in"><FONT FACE="Courier New, monospace"><FONT SIZE=2>#define +_TASK_PRIORITY</FONT></FONT></P> +<P CLASS="western" STYLE="margin-left: 0.98in; margin-bottom: 0in"><FONT FACE="Courier New, monospace"><FONT SIZE=2>#include +<TaskScheduler.h></FONT></FONT></P> +<P CLASS="western" STYLE="margin-left: 0.98in; margin-bottom: 0in"><BR> +</P> +<P CLASS="western" STYLE="margin-left: 0.98in; margin-bottom: 0in"><FONT FACE="Courier New, monospace"><FONT SIZE=2>Scheduler +r, hpr;</FONT></FONT></P> +<P CLASS="western" STYLE="margin-left: 0.98in; margin-bottom: 0in"><BR> +</P> +<P CLASS="western" STYLE="margin-left: 0.98in; margin-bottom: 0in"><FONT FACE="Courier New, monospace"><FONT SIZE=2>// +Tasks</FONT></FONT></P> +<P CLASS="western" STYLE="margin-left: 0.98in; margin-bottom: 0in"><FONT FACE="Courier New, monospace"><FONT SIZE=2>Task +t1(1000, TASK_FOREVER, &tCallback, &r); //base priority</FONT></FONT></P> +<P CLASS="western" STYLE="margin-left: 0.98in; margin-bottom: 0in"><FONT FACE="Courier New, monospace"><FONT SIZE=2>Task +t2(2000, TASK_FOREVER, &tCallback, &r);</FONT></FONT></P> +<P CLASS="western" STYLE="margin-left: 0.98in; margin-bottom: 0in"><FONT FACE="Courier New, monospace"><FONT SIZE=2>Task +t3(3000, TASK_FOREVER, &tCallback, &r);</FONT></FONT></P> +<P CLASS="western" STYLE="margin-left: 0.98in; margin-bottom: 0in"><BR> +</P> +<P CLASS="western" STYLE="margin-left: 0.98in; margin-bottom: 0in"><FONT FACE="Courier New, monospace"><FONT SIZE=2>Task +t4(10, TASK_FOREVER, &tCallback, &hpr); // higher priority</FONT></FONT></P> +<P CLASS="western" STYLE="margin-left: 0.98in; margin-bottom: 0in"><FONT FACE="Courier New, monospace"><FONT SIZE=2>Task +t5(100, TASK_FOREVER, &tCallback, &hpr); //higher priority</FONT></FONT></P> +<P CLASS="western" STYLE="margin-left: 0.98in; margin-bottom: 0in"><BR> +</P> +<P CLASS="western" STYLE="margin-left: 0.98in; margin-bottom: 0in">…</P> +<P CLASS="western" STYLE="margin-left: 0.98in; margin-bottom: 0in"><BR> +</P> +<P CLASS="western" STYLE="margin-left: 0.98in; margin-bottom: 0in"><FONT FACE="Courier New, monospace"><FONT SIZE=2>void +setup () {</FONT></FONT></P> +<P CLASS="western" STYLE="margin-left: 0.98in; margin-bottom: 0in"> +</P> +<P CLASS="western" STYLE="margin-left: 0.98in; margin-bottom: 0in"> +…</P> +<P CLASS="western" STYLE="margin-left: 0.98in; margin-bottom: 0in"><BR> +</P> +<P CLASS="western" STYLE="margin-left: 0.98in; margin-bottom: 0in"> +<FONT FACE="Courier New, monospace"><FONT SIZE=2>r.setHighPriorityScheduler(&hpr); +</FONT></FONT> +</P> +<P CLASS="western" STYLE="margin-left: 0.98in; margin-bottom: 0in"> +<FONT FACE="Courier New, monospace"><FONT SIZE=2>r.enableAll(true); +// this will recursively enable the higher priority tasks as well</FONT></FONT></P> +<P CLASS="western" STYLE="margin-left: 0.98in; margin-bottom: 0in"><FONT FACE="Courier New, monospace"><FONT SIZE=2>}</FONT></FONT></P> +<P CLASS="western" STYLE="margin-left: 0.49in; margin-bottom: 0in"><BR> +</P> +<OL START=3> <LI><P CLASS="western" STYLE="margin-bottom: 0in"><FONT FACE="Times New Roman, serif"><B>FUTHER INFROMATION</B></FONT></P> </OL> @@ -2818,7 +3129,7 @@ time examples of TaskScheduler are available here:</FONT></FONT></P> <P CLASS="western" STYLE="margin-bottom: 0in"><BR> </P> <DIV TYPE=FOOTER> - <P STYLE="margin-top: 0.35in; margin-bottom: 0in"> <SDFIELD TYPE=PAGE SUBTYPE=RANDOM FORMAT=ARABIC>31</SDFIELD></P> + <P STYLE="margin-top: 0.35in; margin-bottom: 0in"> <SDFIELD TYPE=PAGE SUBTYPE=RANDOM FORMAT=ARABIC>33</SDFIELD></P> </DIV> </BODY> -</HTML>
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