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    17. 

  17. 		P { margin-bottom: 0.08in; direction: ltr; color: #000000; widows: 0; orphans: 0 }
    18. 

  18. 		P.western { font-family: "Liberation Serif", "Times New Roman", serif; font-size: 12pt; so-language: en-US }
    19. 

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    23. 

  23. </HEAD>
    24. 

  24. <BODY LANG="en-US" TEXT="#000000" DIR="LTR">
    25. 

  25. <P CLASS="western" STYLE="margin-bottom: 0in"><B>Task Scheduler –
    26. 

  26. cooperative multitasking for Arduino microcontrollers</B></P>
    27. 

  27. <P CLASS="western" STYLE="margin-bottom: 0in"><B>Version 1.6:
    28. 

  28. 2015-09-22</B></P>
    29. 

  29. <P CLASS="western" STYLE="margin-bottom: 0in"><BR>
    30. 

  30. </P>
    31. 

  31. <P CLASS="western" STYLE="margin-bottom: 0in"><B>REQUIREMENT</B>:</P>
    32. 

  32. <P CLASS="western" STYLE="margin-bottom: 0in">A lightweight
    33. 

  33. implementation of the task scheduling supporting:</P>
    34. 

  34. <OL>
    35. 

  35. 	<LI><P CLASS="western" STYLE="margin-bottom: 0in">execution period
    36. 

  36. 	(n times per second)</P>
    37. 

  37. 	<LI><P CLASS="western" STYLE="margin-bottom: 0in">number of
    38. 

  38. 	iterations (n times)</P>
    39. 

  39. 	<LI><P CLASS="western" STYLE="margin-bottom: 0in">execution of tasks
    40. 

  40. 	in predefined sequence</P>
    41. 

  41. 	<LI><P CLASS="western" STYLE="margin-bottom: 0in">dynamic change of
    42. 

  42. 	the execution parameters for both tasks and execution schedule</P>
    43. 

  43. 	<LI><P CLASS="western" STYLE="margin-bottom: 0in">power saving via
    44. 

  44. 	entering IDLE sleep mode if no tasks are scheduled to run</P>
    45. 

  45. </OL>
    46. 

  46. <P CLASS="western" STYLE="margin-bottom: 0in"><BR>
    47. 

  47. </P>
    48. 

  48. <P CLASS="western" STYLE="margin-bottom: 0in"><B>IDEA</B>:</P>
    49. 

  49. <P CLASS="western" STYLE="margin-bottom: 0in">“Task” is a
    50. 

  50. container concept that links together:</P>
    51. 

  51. <OL>
    52. 

  52. 	<LI><P CLASS="western" STYLE="margin-bottom: 0in">Execution interval</P>
    53. 

  53. 	<LI><P CLASS="western" STYLE="margin-bottom: 0in">Number of
    54. 

  54. 	execution iterations</P>
    55. 

  55. 	<LI><P CLASS="western" STYLE="margin-bottom: 0in">A piece of code
    56. 

  56. 	performing the task activities (callback function)</P>
    57. 

  57. </OL>
    58. 

  58. <P CLASS="western" STYLE="margin-bottom: 0in"><BR>
    59. 

  59. </P>
    60. 

  60. <P CLASS="western" STYLE="margin-bottom: 0in">Tasks are linked into
    61. 

  61. execution chains, which are processed by the “Scheduler” in the
    62. 

  62. order they are linked.</P>
    63. 

  63. <P CLASS="western" STYLE="margin-bottom: 0in"><BR>
    64. 

  64. </P>
    65. 

  65. <P CLASS="western" STYLE="margin-bottom: 0in">Tasks are responsible
    66. 

  66. for supporting cooperative multitasking by being “good neighbors”,
    67. 

  67. i.e., running their callback functions in a non-blocking way and
    68. 

  68. releasing control as soon as possible. 
    69. 

  69. </P>
    70. 

  70. <P CLASS="western" STYLE="margin-bottom: 0in"><BR>
    71. 

  71. </P>
    72. 

  72. <P CLASS="western" STYLE="margin-bottom: 0in">“Scheduler” is
    73. 

  73. executing Tasks' callback functions in the order the tasks were added
    74. 

  74. to the chain, from first to last. Scheduler stops and exists after
    75. 

  75. processing the chain once in order to allow other statements in the
    76. 

  76. main code of <B>loop()</B> function to run.  This a “scheduling
    77. 

  77. pass”.</P>
    78. 

  78. <P CLASS="western" STYLE="margin-bottom: 0in"><BR>
    79. 

  79. </P>
    80. 

  80. <P CLASS="western" STYLE="margin-bottom: 0in">If compiled with
    81. 

  81. <FONT FACE="Courier New, monospace">_TASK_SLEEP_ON_IDLE_RUN</FONT>
    82. 

  82. enabled, the scheduler will place processor into IDLE sleep mode (for
    83. 

  83. approximately 1 ms, as the timer interrupt will wake it up), after
    84. 

  84. what is determined to be an “idle” pass. An Idle Pass is a pass
    85. 

  85. through the chain when no Tasks were scheduled to run their callback
    86. 

  86. functions. This is done to avoid repetitive empty passes through the
    87. 

  87. chain when no tasks need to be executed. If any of the tasks in the
    88. 

  88. chain always requires immediate execution (aInterval = 0), then there
    89. 

  89. will be no end-of-pass delay.</P>
    90. 

  90. <P CLASS="western" STYLE="margin-bottom: 0in"><BR>
    91. 

  91. </P>
    92. 

  92. <P CLASS="western" STYLE="margin-bottom: 0in"><B>Note: </B>Task
    93. 

  93. Scheduler uses <B>millis()</B> to determine if tasks are ready to be
    94. 

  94. invoked. Therefore, if you put your device to any “deep” sleep
    95. 

  95. mode disabling timer interrupts, the <B>millis()</B> count will be
    96. 

  96. suspended, leading to effective suspension of scheduling. Upon wake
    97. 

  97. up, active tasks need to be re-enabled, which will effectively reset
    98. 

  98. their internal time scheduling variables to the new value of
    99. 

  99. <B>millis(). </B>Time spent in deep sleep mode should be considered
    100. 

  100. “frozen”, i.e., if a task was scheduled to run in 1 second from
    101. 

  101. now, and device was put to sleep for 5 minutes, upon wake up, the
    102. 

  102. task will still be scheduled 1 second from the time of wake up.
    103. 

  103. Executing <B>enable() </B>function on this tasks will make it run as
    104. 

  104. soon as possible. This is a concern only for tasks which are required
    105. 

  105. to run in a truly periodical manner (in absolute time terms). 
    106. 

  106. </P>
    107. 

  107. <P CLASS="western" STYLE="margin-bottom: 0in"><BR>
    108. 

  108. </P>
    109. 

  109. <P CLASS="western" STYLE="margin-bottom: 0in"><B>COMPILE PARAMETERS:</B></P>
    110. 

  110. <P CLASS="western" STYLE="margin-bottom: 0in">This library could be
    111. 

  111. compiled with several options. 
    112. 

  112. </P>
    113. 

  113. <P CLASS="western" STYLE="margin-bottom: 0in">These parameters must
    114. 

  114. be defined before inclusion of the library header file into the
    115. 

  115. sketch.</P>
    116. 

  116. <P CLASS="western" STYLE="margin-bottom: 0in"><BR>
    117. 

  117. </P>
    118. 

  118. <P CLASS="western" STYLE="margin-bottom: 0in">#define
    119. 

  119. <B>_TASK_TIMECRITICAL</B></P>
    120. 

  120. <P CLASS="western" STYLE="margin-bottom: 0in">...will compile the
    121. 

  121. library with time critical tracking option enabled.</P>
    122. 

  122. <P CLASS="western" STYLE="margin-bottom: 0in">Time critical option
    123. 

  123. keeps track where next execution time of the task falls, and makes it
    124. 

  124. available via API through Task::<B> getOverrun() </B>function. If
    125. 

  125. <B>getOverrun </B>returns a negative value, this Task’s next
    126. 

  126. execution time is in the past, and task is behind schedule. This most
    127. 

  127. probably means that either task’s callback function runtime is too
    128. 

  128. long, or the execution interval is too short (then schedule is too
    129. 

  129. aggressive).</P>
    130. 

  130. <P CLASS="western" STYLE="margin-bottom: 0in">A positive value
    131. 

  131. indicates that task is on schedule, and callback functions have
    132. 

  132. enough time to finish before the next scheduled pass. 
    133. 

  133. </P>
    134. 

  134. <P CLASS="western" STYLE="margin-bottom: 0in"><BR>
    135. 

  135. </P>
    136. 

  136. <P CLASS="western" STYLE="margin-bottom: 0in">#define
    137. 

  137. <B>_TASK_SLEEP_ON_IDLE_RUN</B></P>
    138. 

  138. <P CLASS="western" STYLE="margin-bottom: 0in">...will compile the
    139. 

  139. library with the <B>sleep</B> option enabled (AVR boards only).</P>
    140. 

  140. <P CLASS="western" STYLE="margin-bottom: 0in">When enabled, scheduler
    141. 

  141. will put the microcontroller into <B>SLEEP_MODE_IDLE</B> state if
    142. 

  142. none of the tasks’ callback functions were activated during pass.
    143. 

  143. <B>IDLE</B> state is interrupted by timers once every 1 ms. Helps
    144. 

  144. conserve power.  Device in SLEEP_MODE_IDLE wakes up to all hardware
    145. 

  145. and timer interrupts, so scheduling is kept current.</P>
    146. 

  146. <P CLASS="western" STYLE="margin-bottom: 0in"><BR>
    147. 

  147. </P>
    148. 

  148. <P CLASS="western" STYLE="margin-bottom: 0in"><B>NOTE: above
    149. 

  149. parameters are DISABLED by default, and need to be explicitly
    150. 

  150. enabled.</B></P>
    151. 

  151. <P CLASS="western" STYLE="margin-bottom: 0in"><BR>
    152. 

  152. </P>
    153. 

  153. <P CLASS="western" STYLE="margin-bottom: 0in"><BR>
    154. 

  154. </P>
    155. 

  155. <P CLASS="western" STYLE="margin-bottom: 0in"><BR>
    156. 

  156. </P>
    157. 

  157. <P CLASS="western" STYLE="margin-bottom: 0in"><B>API DOCUMENTATION:</B></P>
    158. 

  158. <P CLASS="western" STYLE="margin-bottom: 0in"><BR>
    159. 

  159. </P>
    160. 

  160. <P CLASS="western" STYLE="margin-bottom: 0in"><B>TASKS:</B></P>
    161. 

  161. <P CLASS="western" STYLE="margin-bottom: 0in"><BR>
    162. 

  162. </P>
    163. 

  163. <P CLASS="western" STYLE="margin-bottom: 0in">CREATION:</P>
    164. 

  164. <P CLASS="western" STYLE="margin-bottom: 0in"><B>Task();</B></P>
    165. 

  165. <P CLASS="western" STYLE="margin-bottom: 0in"><BR>
    166. 

  166. </P>
    167. 

  167. <P CLASS="western" STYLE="margin-left: 0.49in; margin-bottom: 0in">Default
    168. 

  168. constructor. 
    169. 

  169. </P>
    170. 

  170. <P CLASS="western" STYLE="margin-left: 0.49in; margin-bottom: 0in">Takes
    171. 

  171. no parameters and creates a task that could be scheduled to run at
    172. 

  172. every scheduling pass indefinitely, but does not have a callback
    173. 

  173. function defined, so no execution will actually take place. 
    174. 

  174. </P>
    175. 

  175. <P CLASS="western" STYLE="margin-left: 0.49in; margin-bottom: 0in">All
    176. 

  176. tasks are created <B>disabled</B> by default.</P>
    177. 

  177. <P CLASS="western" STYLE="margin-bottom: 0in"><BR>
    178. 

  178. </P>
    179. 

  179. <P CLASS="western" STYLE="margin-bottom: 0in; page-break-after: avoid">
    180. 

  180. <B>Task(unsigned long aInterval, long aIterations, void
    181. 

  181. (*aCallback)(), Scheduler* aScheduler, bool aEnable);</B></P>
    182. 

  182. <P CLASS="western" STYLE="margin-left: 0.49in; margin-bottom: 0in"><BR>
    183. 

  183. </P>
    184. 

  184. <P CLASS="western" STYLE="margin-left: 0.49in; margin-bottom: 0in">Constructor
    185. 

  185. with parameters. 
    186. 

  186. </P>
    187. 

  187. <P CLASS="western" STYLE="margin-left: 0.49in; margin-bottom: 0in">Creates
    188. 

  188. a task that is scheduled to run every &lt;aInterval&gt; milliseconds,
    189. 

  189. &lt;aIterations&gt; times, executing &lt;aCallback&gt; function on
    190. 

  190. every pass. 
    191. 

  191. </P>
    192. 

  192. <OL>
    193. 

  193. 	<LI><P CLASS="western" STYLE="margin-bottom: 0in">aInterval is in
    194. 

  194. 	milliseconds</P>
    195. 

  195. 	<LI><P CLASS="western" STYLE="margin-bottom: 0in">aIteration in
    196. 

  196. 	number of times, -1 for indefinite execution<BR><B>Note: </B>Tasks
    197. 

  197. 	do not remember the number of iteration set initially. After the
    198. 

  198. 	iterations are done, internal iteration counter is 0. If you need to
    199. 

  199. 	perform another set of iterations, you need to set the number of
    200. 

  200. 	iterations again. <BR><B>Note: </B>Tasks which performed all their
    201. 

  201. 	iterations remain active. 
    202. 

  202. 	</P>
    203. 

  203. 	<LI><P CLASS="western" STYLE="margin-bottom: 0in">aCallback is a
    204. 

  204. 	pointer to a void function without parameters</P>
    205. 

  205. 	<LI><P CLASS="western" STYLE="margin-bottom: 0in">aScheduler –
    206. 

  206. 	<B>optional</B> reference to existing scheduler. If supplied (not
    207. 

  207. 	NULL) this task will be appended to the task chain of the current
    208. 

  208. 	scheduler). <B>Default=NULL</B></P>
    209. 

  209. 	<LI><P CLASS="western" STYLE="margin-bottom: 0in">aEnable –
    210. 

  210. 	<B>optional</B>. Value of <B>true </B>will create task enabled.
    211. 

  211. 	<B>Default = false</B></P>
    212. 

  212. </OL>
    213. 

  213. <P CLASS="western" STYLE="margin-left: 0.49in; margin-bottom: 0in"><BR>
    214. 

  214. </P>
    215. 

  215. <P CLASS="western" STYLE="margin-left: 0.49in; margin-bottom: 0in">All
    216. 

  216. tasks are created <B>disabled</B> by default (unless aEnable = true).
    217. 

  217. You have to explicitly enable the task for execution.</P>
    218. 

  218. <P CLASS="western" STYLE="margin-left: 0.49in; margin-bottom: 0in">Enabled
    219. 

  219. task is scheduled for execution immediately. Enable tasks with delay
    220. 

  220. (standard execution interval or specific execution interval) in order
    221. 

  221. to defer first run of the task.</P>
    222. 

  222. <P CLASS="western" STYLE="margin-left: 0.49in; margin-bottom: 0in"><BR>
    223. 

  223. </P>
    224. 

  224. <P CLASS="western" STYLE="margin-bottom: 0in"><B>INFORMATION</B></P>
    225. 

  225. <P CLASS="western" STYLE="margin-left: 0.49in; margin-bottom: 0in">The
    226. 

  226. following 3 “getter” functions return task status
    227. 

  227. (enabled/disabled), execution interval in milliseconds, number of
    228. 

  228. <I><B>remaining</B></I> iterations. 
    229. 

  229. </P>
    230. 

  230. <P CLASS="western" STYLE="margin-left: 0.49in; margin-bottom: 0in"><BR>
    231. 

  231. </P>
    232. 

  232. <P CLASS="western" STYLE="margin-left: 0.49in; margin-bottom: 0in"><B>bool
    233. 

  233. isEnabled() </B>
    234. 

  234. </P>
    235. 

  235. <P CLASS="western" STYLE="margin-left: 0.49in; margin-bottom: 0in"><B>unsigned
    236. 

  236. long getInterval()</B></P>
    237. 

  237. <P CLASS="western" STYLE="margin-left: 0.49in; margin-bottom: 0in"><B>long
    238. 

  238. getIterations() </B>
    239. 

  239. </P>
    240. 

  240. <P CLASS="western" STYLE="margin-left: 0.49in; margin-bottom: 0in"><BR>
    241. 

  241. </P>
    242. 

  242. <P CLASS="western" STYLE="margin-bottom: 0in"><B>long getOverrun()</B></P>
    243. 

  243. <P CLASS="western" STYLE="margin-left: 0.49in; margin-bottom: 0in">If
    244. 

  244. library is compiled with <FONT FACE="Courier New, monospace">_TASK_TIMECRITICAL</FONT>
    245. 

  245. enabled, tasks are monitored for “long running” scenario. A “long
    246. 

  246. running” task is a task that does not finish processing its
    247. 

  247. callback functions quickly, and thus creates a situation for itself
    248. 

  248. and other tasks where they don't run on a scheduled interval, but
    249. 

  249. rather “catch up” and are behind.  When task scheduler sets the
    250. 

  250. next execution target time, it adds Task's execution interval to the
    251. 

  251. previously scheduled execution time:</P>
    252. 

  252. <P CLASS="western" STYLE="margin-left: 0.49in; margin-bottom: 0in">	<B>next
    253. 

  253. execution time = previous execution time + task execution interval</B></P>
    254. 

  254. <P CLASS="western" STYLE="margin-left: 0.49in; margin-bottom: 0in"><BR>
    255. 

  255. </P>
    256. 

  256. <P CLASS="western" STYLE="margin-left: 0.49in; margin-bottom: 0in">If
    257. 

  257. <B>next execution time</B> happens to be already in the past (<B>next
    258. 

  258. execution time</B> &lt; <B>millis()</B>), then task is considered
    259. 

  259. <I><B>overrun</B></I>. <B>GetOverrun</B> function returns number of
    260. 

  260. milliseconds between next execution time and current time. If the
    261. 

  261. <B>value is negative</B>, the task is overrun by that many
    262. 

  262. milliseconds. 
    263. 

  263. </P>
    264. 

  264. <P CLASS="western" STYLE="margin-left: 0.49in; margin-bottom: 0in">Positive
    265. 

  265. value indicate number of milliseconds of slack this task has for
    266. 

  266. execution purposes. 
    267. 

  267. </P>
    268. 

  268. <P CLASS="western" STYLE="margin-left: 0.49in; margin-bottom: 0in"><BR>
    269. 

  269. </P>
    270. 

  270. <P CLASS="western" STYLE="margin-bottom: 0in"><B>bool
    271. 

  271. isFirstIteration()</B></P>
    272. 

  272. <P CLASS="western" STYLE="margin-bottom: 0in"><B>bool
    273. 

  273. isLastIteration()</B></P>
    274. 

  274. <P CLASS="western" STYLE="margin-left: 0.49in; margin-bottom: 0in">For
    275. 

  275. tasks with a defined number of iterations, indicates whether current
    276. 

  276. pass is a first or a last iteration of the task (respectively). 
    277. 

  277. </P>
    278. 

  278. <P CLASS="western" STYLE="margin-bottom: 0in"><BR>
    279. 

  279. </P>
    280. 

  280. <P CLASS="western" STYLE="margin-bottom: 0in; page-break-after: avoid">
    281. 

  281. <B>CONTROL:</B></P>
    282. 

  282. <P CLASS="western" STYLE="margin-bottom: 0in"><BR>
    283. 

  283. </P>
    284. 

  284. <P CLASS="western" STYLE="margin-bottom: 0in"><B>void enable();</B></P>
    285. 

  285. <P CLASS="western" STYLE="margin-bottom: 0in"><BR>
    286. 

  286. </P>
    287. 

  287. <P CLASS="western" STYLE="margin-left: 0.49in; margin-bottom: 0in">Enables
    288. 

  288. the task, and schedules it for immediate execution (without delay) at
    289. 

  289. this or next scheduling pass depending on when the task was enabled.
    290. 

  290. Scheduler will execute the next pass without any delay because there
    291. 

  291. is a task which was enabled and requires execution. 
    292. 

  292. </P>
    293. 

  293. <P CLASS="western" STYLE="margin-left: 0.49in; margin-bottom: 0in"><BR>
    294. 

  294. </P>
    295. 

  295. <P CLASS="western" STYLE="margin-bottom: 0in"><B>void delay();</B></P>
    296. 

  296. <P CLASS="western" STYLE="margin-bottom: 0in"><BR>
    297. 

  297. </P>
    298. 

  298. <P CLASS="western" STYLE="margin-left: 0.49in; margin-bottom: 0in">Schedules
    299. 

  299. the task for execution after a delay (aInterval), but does not change
    300. 

  300. the enabled/disabled status of the task. 
    301. 

  301. </P>
    302. 

  302. <P CLASS="western" STYLE="margin-left: 0.49in; margin-bottom: 0in"><BR>
    303. 

  303. </P>
    304. 

  304. <P CLASS="western" STYLE="margin-bottom: 0in"><B>void
    305. 

  305. enableDelayed();</B></P>
    306. 

  306. <P CLASS="western" STYLE="margin-bottom: 0in"><BR>
    307. 

  307. </P>
    308. 

  308. <P CLASS="western" STYLE="margin-left: 0.49in; margin-bottom: 0in">Enables
    309. 

  309. the task, and schedules it for execution after a delay (aInterval). 
    310. 

  310. </P>
    311. 

  311. <P CLASS="western" STYLE="margin-left: 0.49in; margin-bottom: 0in"><BR>
    312. 

  312. </P>
    313. 

  313. <P CLASS="western" STYLE="margin-bottom: 0in"><B>void enableDelayed
    314. 

  314. (unsigned long aDelay);</B></P>
    315. 

  315. <P CLASS="western" STYLE="margin-bottom: 0in"><BR>
    316. 

  316. </P>
    317. 

  317. <P CLASS="western" STYLE="margin-left: 0.49in; margin-bottom: 0in">Enables
    318. 

  318. the task, and schedules it for execution after a specific delay
    319. 

  319. (aDelay, which maybe different from aInterval). 
    320. 

  320. </P>
    321. 

  321. <P CLASS="western" STYLE="margin-left: 0.49in; margin-bottom: 0in"><BR>
    322. 

  322. </P>
    323. 

  323. <P CLASS="western" STYLE="margin-bottom: 0in"><B>void restart();</B></P>
    324. 

  324. <P CLASS="western" STYLE="margin-bottom: 0in"><BR>
    325. 

  325. </P>
    326. 

  326. <P CLASS="western" STYLE="margin-left: 0.49in; margin-bottom: 0in">For
    327. 

  327. tasks with limited number of iterations only, <B>restart</B> function
    328. 

  328. will re-enable the task, set the number of iterations back to when
    329. 

  329. the task was created and and schedule the task for execution as soon
    330. 

  330. as possible.</P>
    331. 

  331. <P CLASS="western" STYLE="margin-left: 0.49in; margin-bottom: 0in"><BR>
    332. 

  332. </P>
    333. 

  333. <P CLASS="western" STYLE="margin-bottom: 0in"><B>void restartDelayed
    334. 

  334. (unsigned long aDelay);</B></P>
    335. 

  335. <P CLASS="western" STYLE="margin-bottom: 0in"><BR>
    336. 

  336. </P>
    337. 

  337. <P CLASS="western" STYLE="margin-left: 0.49in; margin-bottom: 0in">Same
    338. 

  338. as <B>restart() </B>function, with the only difference being that
    339. 

  339. Task is scheduled to run first iteration after a delay = <B>aDelay</B>
    340. 

  340. milliseconds.</P>
    341. 

  341. <P CLASS="western" STYLE="margin-bottom: 0in"><BR>
    342. 

  342. </P>
    343. 

  343. <P CLASS="western" STYLE="margin-bottom: 0in"><B>void disable();</B></P>
    344. 

  344. <P CLASS="western" STYLE="margin-bottom: 0in"><BR>
    345. 

  345. </P>
    346. 

  346. <P CLASS="western" STYLE="margin-left: 0.49in; margin-bottom: 0in">Disables
    347. 

  347. the task. Scheduler will not execute this task any longer, even if it
    348. 

  348. remains in the chain.  Task can be later re-enabled for execution. 
    349. 

  349. </P>
    350. 

  350. <P CLASS="western" STYLE="margin-left: 0.49in; margin-bottom: 0in"><BR>
    351. 

  351. </P>
    352. 

  352. <P CLASS="western" STYLE="margin-bottom: 0in"><B>void set(unsigned
    353. 

  353. long aInterval, long aIterations, void (*aCallback)());</B></P>
    354. 

  354. <P CLASS="western" STYLE="margin-bottom: 0in"><BR>
    355. 

  355. </P>
    356. 

  356. <P CLASS="western" STYLE="margin-left: 0.49in; margin-bottom: 0in">Allows
    357. 

  357. dynamic control of all task execution parameters in one function
    358. 

  358. call. 
    359. 

  359. </P>
    360. 

  360. <P CLASS="western" STYLE="margin-left: 0.49in; margin-bottom: 0in"><BR>
    361. 

  361. </P>
    362. 

  362. <P CLASS="western" STYLE="margin-bottom: 0in">Next three “setter”
    363. 

  363. functions allow changes of individual task execution control
    364. 

  364. parameters. 
    365. 

  365. </P>
    366. 

  366. <P CLASS="western" STYLE="margin-left: 0.49in; margin-bottom: 0in"><B>void
    367. 

  367. setInterval (unsigned long aInterval) </B>
    368. 

  368. </P>
    369. 

  369. <P CLASS="western" STYLE="margin-left: 0.49in; margin-bottom: 0in"><B>void
    370. 

  370. setIterations (long aIterations) </B>
    371. 

  371. </P>
    372. 

  372. <P CLASS="western" STYLE="margin-left: 0.49in; margin-bottom: 0in"><B>void
    373. 

  373. setCallback (void (*aCallback)()) </B>
    374. 

  374. </P>
    375. 

  375. <P CLASS="western" STYLE="margin-bottom: 0in"><BR>
    376. 

  376. </P>
    377. 

  377. <P CLASS="western" STYLE="margin-bottom: 0in"><B>Note: </B>Next
    378. 

  378. execution time calculation takes place <B>after</B> the callback
    379. 

  379. function is called, so new interval will be used immediately by the
    380. 

  380. scheduler. For the situations when one task is changing the interval
    381. 

  381. parameter for the other, <B>setInterval</B> function calls <B>delay
    382. 

  382. </B>explicitly to guarantee schedule change, however it <B>does not
    383. 

  383. </B>enable the task if task is disabled.</P>
    384. 

  384. <P CLASS="western" STYLE="margin-bottom: 0in"><B>Note: </B><SPAN STYLE="font-weight: normal">Tasks
    385. 

  385. that ran through all their allocated iterations are disabled.
    386. 

  386. </SPAN><B>SetIterations()</B><SPAN STYLE="font-weight: normal">
    387. 

  387. method </SPAN><B>DOES NOT</B><SPAN STYLE="font-weight: normal">
    388. 

  388. enable the task. Either enable explicitly, or use restart methods. </SPAN>
    389. 

  389. </P>
    390. 

  390. <P CLASS="western" STYLE="margin-bottom: 0in"><BR>
    391. 

  391. </P>
    392. 

  392. <P CLASS="western" STYLE="margin-bottom: 0in"><BR>
    393. 

  393. </P>
    394. 

  394. <P CLASS="western" STYLE="margin-bottom: 0in"><B>TASK SCHEDULER:</B></P>
    395. 

  395. <P CLASS="western" STYLE="margin-bottom: 0in"><BR>
    396. 

  396. </P>
    397. 

  397. <P CLASS="western" STYLE="margin-bottom: 0in"><B>CREATION:</B></P>
    398. 

  398. <P CLASS="western" STYLE="margin-bottom: 0in"><BR>
    399. 

  399. </P>
    400. 

  400. <P CLASS="western" STYLE="margin-bottom: 0in"><B>Scheduler()</B><BR><BR>
    401. 

  401. </P>
    402. 

  402. <P CLASS="western" STYLE="margin-left: 0.49in; margin-bottom: 0in">Default
    403. 

  403. constructor. 
    404. 

  404. </P>
    405. 

  405. <P CLASS="western" STYLE="margin-left: 0.49in; margin-bottom: 0in">Takes
    406. 

  406. no parameters. Creates task scheduler with default parameters and an
    407. 

  407. empty task queue. 
    408. 

  408. </P>
    409. 

  409. <P CLASS="western" STYLE="margin-left: 0.49in; margin-bottom: 0in"><BR>
    410. 

  410. </P>
    411. 

  411. <P CLASS="western" STYLE="margin-bottom: 0in"><B>void init()</B></P>
    412. 

  412. <P CLASS="western" STYLE="margin-left: 0.49in; margin-bottom: 0in"><BR>
    413. 

  413. </P>
    414. 

  414. <P CLASS="western" STYLE="margin-left: 0.49in; margin-bottom: 0in">Initializes
    415. 

  415. the task queue and scheduler parameters, Executed as part of
    416. 

  416. constructor, so don't need to be explicitly called after creation.</P>
    417. 

  417. <P CLASS="western" STYLE="margin-left: 0.49in; margin-bottom: 0in"><B>Note:
    418. 

  418. </B>be default (if compiled with <FONT FACE="Courier New, monospace">_TASK_TIMECRITICAL</FONT>
    419. 

  419. enabled) scheduler is allowed to put processor to IDLE sleep mode. If
    420. 

  420. this behavior was changed via <B>allowSleep() </B>function, <B>inti()
    421. 

  421. </B>will <B>NOT</B> reset allow sleep particular parameter. 
    422. 

  422. </P>
    423. 

  423. <P CLASS="western" STYLE="margin-bottom: 0in"><BR><B>void
    424. 

  424. addTask(Task&amp; aTask)</B></P>
    425. 

  425. <P CLASS="western" STYLE="margin-left: 0.49in; margin-bottom: 0in"><BR>
    426. 

  426. </P>
    427. 

  427. <P CLASS="western" STYLE="margin-left: 0.49in; margin-bottom: 0in">Adds
    428. 

  428. task aTask to the execution queue (or chain) of tasks by appending it
    429. 

  429. to the end of the chain. If two tasks are scheduled for execution,
    430. 

  430. the sequence will match the order tasks are appended to the chain.
    431. 

  431. However, in reality, due to different timing of task execution, the
    432. 

  432. actual order will be different. 
    433. 

  433. </P>
    434. 

  434. <P CLASS="western" STYLE="margin-left: 0.49in; margin-bottom: 0in"><B>Note:
    435. 

  435. </B>Currently, changing the execution dynamically is not supported. 
    436. 

  436. </P>
    437. 

  437. <P CLASS="western" STYLE="margin-left: 0.49in; margin-bottom: 0in">If
    438. 

  438. you need to reorder the queue – initialize the scheduler and re-add
    439. 

  439. the tasks in a different order. 
    440. 

  440. </P>
    441. 

  441. <P CLASS="western" STYLE="margin-bottom: 0in"><BR><B>void
    442. 

  442. deleteTask(Task&amp; aTask)</B></P>
    443. 

  443. <P CLASS="western" STYLE="margin-left: 0.49in; margin-bottom: 0in"><BR>
    444. 

  444. </P>
    445. 

  445. <P CLASS="western" STYLE="margin-left: 0.49in; margin-bottom: 0in">Deletes
    446. 

  446. task aTask from the execution chain. The chain of remaining tasks is
    447. 

  447. linked together (i.e</P>
    448. 

  448. <P CLASS="western" STYLE="margin-left: 0.49in; margin-bottom: 0in">if
    449. 

  449. original task chain is 1 → 2 → 3 → 4, deleting 3 will result in
    450. 

  450. 1 → 2 → 4).</P>
    451. 

  451. <P CLASS="western" STYLE="margin-left: 0.49in; margin-bottom: 0in"><B>Note:
    452. 

  452. </B>it is not required to delete a task from the chain. A disabled
    453. 

  453. task will not be executed anyway, but you save a few microseconds per
    454. 

  454. scheduling pass by deleting it, since it is not even considered for
    455. 

  455. execution. 
    456. 

  456. </P>
    457. 

  457. <P CLASS="western" STYLE="margin-left: 0.49in; margin-bottom: 0in">An
    458. 

  458. example of proper use of this function would be running some sort of
    459. 

  459. <B>initialize</B> task in the chain, and then deleting it from the
    460. 

  460. chain since it only needs to run once. 
    461. 

  461. </P>
    462. 

  462. <P CLASS="western" STYLE="margin-left: 0.49in; margin-bottom: 0in"><BR>
    463. 

  463. </P>
    464. 

  464. <P CLASS="western" STYLE="margin-bottom: 0in"><B>void allowSleep(bool
    465. 

  465. aState) </B>
    466. 

  466. </P>
    467. 

  467. <P CLASS="western" STYLE="margin-left: 0.49in; margin-bottom: 0in"><BR>
    468. 

  468. </P>
    469. 

  469. <P CLASS="western" STYLE="margin-left: 0.49in; margin-bottom: 0in">Available
    470. 

  470. in API only  if compiled with <FONT FACE="Courier New, monospace">_TASK_TIMECRITICAL</FONT>
    471. 

  471. enabled. Controls whether scheduler is allowed (<B>aState =true</B>),
    472. 

  472. or not (<B>aState =false</B>) to put processor into IDLE sleep mode
    473. 

  473. in case not tasks are scheduled to run.</P>
    474. 

  474. <P CLASS="western" STYLE="margin-left: 0.49in; margin-bottom: 0in">The
    475. 

  475. <B>default</B> behavior of scheduler upon creation is to allow sleep
    476. 

  476. mode. 
    477. 

  477. </P>
    478. 

  478. <P CLASS="western" STYLE="margin-bottom: 0in"><BR><B>void enableAll()</B></P>
    479. 

  479. <P CLASS="western" STYLE="margin-bottom: 0in"><B>void disableAll()</B></P>
    480. 

  480. <P CLASS="western" STYLE="margin-bottom: 0in"><BR>
    481. 

  481. </P>
    482. 

  482. <P CLASS="western" STYLE="margin-left: 0.49in; margin-bottom: 0in">enables
    483. 

  483. and disables (respectively) all tasks in the chain. Convenient if
    484. 

  484. your need to enable/disable majority of the tasks (i.e. disable all
    485. 

  485. and then enable one). 
    486. 

  486. </P>
    487. 

  487. <P CLASS="western" STYLE="margin-bottom: 0in"><BR><B>Task&amp;
    488. 

  488. currentTask()<BR></B><BR>
    489. 

  489. </P>
    490. 

  490. <P CLASS="western" STYLE="margin-left: 0.49in; margin-bottom: 0in">Returns
    491. 

  491. reference to the task, currently executing via <B>execute()</B> loop.
    492. 

  492. Could be used by callback functions to identify which of the 
    493. 

  493. </P>
    494. 

  494. <P CLASS="western" STYLE="margin-bottom: 0in"><BR><B>void execute()</B></P>
    495. 

  495. <P CLASS="western" STYLE="margin-bottom: 0in"><BR>
    496. 

  496. </P>
    497. 

  497. <P CLASS="western" STYLE="margin-left: 0.49in; margin-bottom: 0in">Executes
    498. 

  498. one scheduling pass, including end-of-pass sleep. This function
    499. 

  499. typically placed inside the <B>loop()</B> function of the sketch.
    500. 

  500. Since <B>execute</B> exits after every pass, you can put additional
    501. 

  501. statements after <B>execute</B> inside the <B>loop()</B> 
    502. 

  502. </P>
    503. 

  503. <P CLASS="western" STYLE="margin-left: 0.49in; margin-bottom: 0in"><BR>
    504. 

  504. </P>
    505. 

  505. <P CLASS="western" STYLE="margin-left: 0.49in; margin-bottom: 0in"><BR>
    506. 

  506. </P>
    507. 

  507. <P CLASS="western" STYLE="margin-bottom: 0in; page-break-after: avoid">
    508. 

  508. <B>IMPLEMENTATION SCENARIOS AND IDEAS:</B></P>
    509. 

  509. <P CLASS="western" STYLE="margin-bottom: 0in"><BR>
    510. 

  510. </P>
    511. 

  511. <OL>
    512. 

  512. 	<LI><P CLASS="western" STYLE="margin-bottom: 0in"><B>EVENT DRIVEN
    513. 

  513. 	PROGRAMMING</B></P>
    514. 

  514. </OL>
    515. 

  515. <P CLASS="western" STYLE="margin-bottom: 0in"><BR>
    516. 

  516. </P>
    517. 

  517. <P CLASS="western" STYLE="margin-bottom: 0in">Each of the processes
    518. 

  518. of your application becomes a separate and distinct programming area,
    519. 

  519. which may or may not interact and control each other. 
    520. 

  520. </P>
    521. 

  521. <P CLASS="western" STYLE="margin-bottom: 0in"><BR>
    522. 

  522. </P>
    523. 

  523. <P CLASS="western" STYLE="margin-bottom: 0in">Example: 
    524. 

  524. </P>
    525. 

  525. <P CLASS="western" STYLE="margin-bottom: 0in">In a plant watering
    526. 

  526. system you need to measure soil humidity, control pump and display
    527. 

  527. the results</P>
    528. 

  528. <P CLASS="western" STYLE="margin-bottom: 0in">Each of the areas
    529. 

  529. becomes a task:</P>
    530. 

  530. <P CLASS="western" STYLE="margin-bottom: 0in"><BR>
    531. 

  531. </P>
    532. 

  532. <P CLASS="western" STYLE="margin-left: 0.49in; margin-bottom: 0in"><FONT FACE="Courier New, monospace"><FONT SIZE=2>Task
    533. 

  533. <B>tMeasure</B> (TMEASURE_INTERVAL*SECOND, -1,
    534. 

  534. &amp;measureCallback);<BR>Task <B>tWater</B>  
    535. 

  535. (TWATER_INTERVAL*SECOND, RETRIES, &amp;waterCallback);<BR>Task
    536. 

  536. <B>tDisplay</B> (TDISPLAY_INTERVAL*SECOND, -1, &amp;displayCallback);
    537. 

  537. <BR></FONT></FONT><BR>
    538. 

  538. </P>
    539. 

  539. <P CLASS="western" STYLE="margin-left: 0.49in; margin-bottom: 0in"><FONT FACE="Courier New, monospace"><FONT SIZE=2>Scheduler
    540. 

  540. </FONT></FONT><FONT FACE="Courier New, monospace"><FONT SIZE=2><B>taskManager</B></FONT></FONT><FONT FACE="Courier New, monospace"><FONT SIZE=2>;</FONT></FONT><BR><BR>
    541. 

  541. </P>
    542. 

  542. <P CLASS="western" STYLE="margin-bottom: 0in">Further, once you turn
    543. 

  543. on the pump, you keep it running for TWATER_INTERVAL interval and
    544. 

  544. then turn it off. Turning off a pump is also a task which only needs
    545. 

  545. to run once for every time the pump is turned on:</P>
    546. 

  546. <P CLASS="western" STYLE="margin-bottom: 0in"><BR>
    547. 

  547. </P>
    548. 

  548. <P CLASS="western" STYLE="margin-left: 0.49in; margin-bottom: 0in"><FONT FACE="Courier New, monospace"><FONT SIZE=2>Task
    549. 

  549. </FONT></FONT><FONT FACE="Courier New, monospace"><FONT SIZE=2><B>tWaterOff</B></FONT></FONT><FONT FACE="Courier New, monospace"><FONT SIZE=2>
    550. 

  550. (WATERTIME*SECOND, 1,</FONT></FONT><FONT FACE="Courier New, monospace">
    551. 

  551. &amp;waterOffCallback);</FONT><BR><BR>
    552. 

  552. </P>
    553. 

  553. <P CLASS="western" STYLE="margin-bottom: 0in">Example of the callback
    554. 

  554. function:</P>
    555. 

  555. <P CLASS="western" STYLE="margin-bottom: 0in"><BR>
    556. 

  556. </P>
    557. 

  557. <P CLASS="western" STYLE="margin-left: 0.49in; margin-bottom: 0in"><FONT FACE="Courier New, monospace"><FONT SIZE=2>void
    558. 

  558. waterOffCallback() {<BR>    motorOff();<BR>   
    559. 

  559. tWater.enableDelayed();<BR>}</FONT></FONT></P>
    560. 

  560. <P CLASS="western" STYLE="margin-left: 0.49in; margin-bottom: 0in"><BR>
    561. 

  561. </P>
    562. 

  562. <P CLASS="western" STYLE="margin-left: 0.49in; margin-bottom: 0in"><FONT FACE="Courier New, monospace"><FONT SIZE=2>or</FONT></FONT></P>
    563. 

  563. <P CLASS="western" STYLE="margin-left: 0.49in; margin-bottom: 0in"><BR>
    564. 

  564. </P>
    565. 

  565. <P CLASS="western" STYLE="margin-left: 0.49in; margin-bottom: 0in"><FONT FACE="Courier New, monospace"><FONT SIZE=2>void
    566. 

  566. waterCallback() {<BR>    if (tWater.getIterations()) {</FONT></FONT></P>
    567. 

  567. <P CLASS="western" STYLE="margin-left: 0.49in; margin-bottom: 0in"><FONT FACE="Courier New, monospace"><FONT SIZE=2>//
    568. 

  568. If this is not the last iteration = turn the pump on<BR>     
    569. 

  569. motorOn();<BR>      tWaterOff.set(parameters.watertime * SECOND, 1,
    570. 

  570. &amp;waterOffCallback);<BR>      tWaterOff.enableDelayed();<BR>     
    571. 

  571. return;<BR>    }</FONT></FONT></P>
    572. 

  572. <P CLASS="western" STYLE="margin-left: 0.49in; margin-bottom: 0in"><FONT FACE="Courier New, monospace"><FONT SIZE=2>//
    573. 

  573. We could not reach target humidity – something is wrong<BR>   
    574. 

  574. motorOff;<BR>    taskManager.disableAll();<BR>    tError.enable();<BR>}</FONT></FONT></P>
    575. 

  575. <P CLASS="western" STYLE="margin-bottom: 0in"><BR>
    576. 

  576. </P>
    577. 

  577. <P CLASS="western" STYLE="margin-bottom: 0in"><FONT FACE="Times New Roman, serif">Your
    578. 

  578. sample <B>setup</B>() and <B>loop</B>() (partially) are as follows. </FONT>
    579. 

  579. </P>
    580. 

  580. <P CLASS="western" STYLE="margin-bottom: 0in"><FONT FACE="Times New Roman, serif"><B>Note:
    581. 

  581. </B>please note that tWater is <B>not</B> activated during setup().
    582. 

  582. It is activated by tMeasure callback once the watering conditions are
    583. 

  583. met. </FONT>
    584. 

  584. </P>
    585. 

  585. <P CLASS="western" STYLE="margin-bottom: 0in"><BR>
    586. 

  586. </P>
    587. 

  587. <P CLASS="western" STYLE="margin-bottom: 0in"><FONT FACE="Times New Roman, serif">	</FONT><FONT FACE="Courier New, monospace">setup()</FONT></P>
    588. 

  588. <P CLASS="western" STYLE="margin-bottom: 0in"><FONT FACE="Courier New, monospace">	
    589. 

  589.  ...</FONT></P>
    590. 

  590. <P CLASS="western" STYLE="margin-left: 0.49in; margin-bottom: 0in"> 
    591. 

  591. <FONT FACE="Courier New, monospace">tWater.setIterations(parameters.retries);<BR>
    592. 

  592.  tWaterOff.setInterval(parameters.watertime * SECOND);<BR><BR><BR> 
    593. 

  593. taskManager.init();<BR>  taskManager.addTask(tMeasure);<BR> 
    594. 

  594. taskManager.addTask(tDisplay);<BR>  taskManager.addTask(tWater);<BR> 
    595. 

  595. taskManager.addTask(tWaterOff);<BR>  <BR>  tMeasure.enable();<BR> 
    596. 

  596. tDisplay.enable();<BR><BR>  currentHumidity =
    597. 

  597. measureHumidity();<BR>}<BR><BR><BR>void loop ()<BR>{<BR> 
    598. 

  598. taskManager.execute();<BR>}</FONT><FONT FACE="Times New Roman, serif"><BR></FONT><BR>
    599. 

  599. </P>
    600. 

  600. <OL START=2>
    601. 

  601. 	<LI><P CLASS="western" STYLE="margin-bottom: 0in">“<FONT FACE="Times New Roman, serif"><B>NATIVE”
    602. 

  602. 	SUPPORT FOR FINITE STATE MACHINE</B></FONT></P>
    603. 

  603. </OL>
    604. 

  604. <P CLASS="western" STYLE="margin-bottom: 0in"><BR>
    605. 

  605. </P>
    606. 

  606. <P CLASS="western" STYLE="margin-bottom: 0in"><FONT FACE="Times New Roman, serif">Define
    607. 

  607. “states” as callback function or functions. Each callback
    608. 

  608. function executes activities specific to a “state” and then
    609. 

  609. “transitions” to the next state by assigning next callback
    610. 

  610. function to the task. </FONT>
    611. 

  611. </P>
    612. 

  612. <P CLASS="western" STYLE="margin-bottom: 0in"><FONT FACE="Times New Roman, serif">Transition
    613. 

  613. from one state to the next is achieved by setting next callback
    614. 

  614. function at the end of preceding one. </FONT>
    615. 

  615. </P>
    616. 

  616. <P CLASS="western" STYLE="margin-bottom: 0in"><FONT FACE="Times New Roman, serif"><B>Note:
    617. 

  617. </B>do not call the next callback function. Let the schedule take
    618. 

  618. care of that during the next pass. (Thus letting other tasks run). </FONT>
    619. 

  619. </P>
    620. 

  620. <P CLASS="western" STYLE="margin-bottom: 0in"><BR>
    621. 

  621. </P>
    622. 

  622. <P CLASS="western" STYLE="margin-bottom: 0in"><FONT FACE="Times New Roman, serif">Example:
    623. 

  623. Blinking LED 2 times a second could be achieved this way</FONT></P>
    624. 

  624. <P CLASS="western" STYLE="margin-left: 0.49in; margin-bottom: 0in"><BR>
    625. 

  625. </P>
    626. 

  626. <P CLASS="western" STYLE="margin-left: 0.49in; margin-bottom: 0in"><FONT FACE="Courier New, monospace">Task
    627. 

  627. tLedBlinker (500, -1, &amp;ledOnCallback);</FONT></P>
    628. 

  628. <P CLASS="western" STYLE="margin-left: 0.49in; margin-bottom: 0in"><FONT FACE="Courier New, monospace">Scheduler
    629. 

  629. taskManager;</FONT></P>
    630. 

  630. <P CLASS="western" STYLE="margin-left: 0.49in; margin-bottom: 0in"><BR>
    631. 

  631. </P>
    632. 

  632. <P CLASS="western" STYLE="margin-left: 0.49in; margin-bottom: 0in"><FONT FACE="Courier New, monospace">void
    633. 

  633.  ledOnCallback() {</FONT></P>
    634. 

  634. <P CLASS="western" STYLE="margin-left: 0.49in; margin-bottom: 0in"><FONT FACE="Courier New, monospace">	turnLedOn();</FONT></P>
    635. 

  635. <P CLASS="western" STYLE="margin-left: 0.49in; margin-bottom: 0in"><FONT FACE="Courier New, monospace">	tLedBlinker.setCallback(&amp;ledOffCallback);</FONT></P>
    636. 

  636. <P CLASS="western" STYLE="margin-left: 0.49in; margin-bottom: 0in"><FONT FACE="Courier New, monospace">}</FONT></P>
    637. 

  637. <P CLASS="western" STYLE="margin-left: 0.49in; margin-bottom: 0in"><BR>
    638. 

  638. </P>
    639. 

  639. <P CLASS="western" STYLE="margin-left: 0.49in; margin-bottom: 0in"><FONT FACE="Courier New, monospace">void
    640. 

  640.  ledOffCallback() {</FONT></P>
    641. 

  641. <P CLASS="western" STYLE="margin-left: 0.49in; margin-bottom: 0in"><FONT FACE="Courier New, monospace">	turnLedOff();</FONT></P>
    642. 

  642. <P CLASS="western" STYLE="margin-left: 0.49in; margin-bottom: 0in"><FONT FACE="Courier New, monospace">	tLedBlinker.setCallback(&amp;ledOnCallback);</FONT></P>
    643. 

  643. <P CLASS="western" STYLE="margin-left: 0.49in; margin-bottom: 0in"><FONT FACE="Courier New, monospace">}</FONT></P>
    644. 

  644. <P CLASS="western" STYLE="margin-left: 0.49in; margin-bottom: 0in"><BR>
    645. 

  645. </P>
    646. 

  646. <P CLASS="western" STYLE="margin-left: 0.49in; margin-bottom: 0in"><FONT FACE="Courier New, monospace">setup()
    647. 

  647. {</FONT></P>
    648. 

  648. <P CLASS="western" STYLE="margin-left: 0.49in; margin-bottom: 0in"><FONT FACE="Courier New, monospace">	taskManager.init();<BR>
    649. 

  649.  	taskManager.addTask(tLedBlinker);</FONT></P>
    650. 

  650. <P CLASS="western" STYLE="margin-left: 0.49in; margin-bottom: 0in"><FONT FACE="Courier New, monospace">	</FONT></P>
    651. 

  651. <P CLASS="western" STYLE="margin-left: 0.49in; margin-bottom: 0in"><FONT FACE="Courier New, monospace">	tLedBlinker.enable();</FONT></P>
    652. 

  652. <P CLASS="western" STYLE="margin-left: 0.49in; margin-bottom: 0in"><FONT FACE="Courier New, monospace">}</FONT></P>
    653. 

  653. <P CLASS="western" STYLE="margin-left: 0.49in; margin-bottom: 0in"><BR>
    654. 

  654. </P>
    655. 

  655. <P CLASS="western" STYLE="margin-left: 0.49in; margin-bottom: 0in"><FONT FACE="Courier New, monospace">loop
    656. 

  656. () {</FONT></P>
    657. 

  657. <P CLASS="western" STYLE="margin-left: 0.49in; margin-bottom: 0in"><FONT FACE="Courier New, monospace">	taskManager.execute();</FONT></P>
    658. 

  658. <P CLASS="western" STYLE="margin-left: 0.49in; margin-bottom: 0in"><FONT FACE="Courier New, monospace">}</FONT><FONT FACE="Times New Roman, serif"><BR></FONT><BR>
    659. 

  659. </P>
    660. 

  660. <P CLASS="western" STYLE="margin-bottom: 0in"><FONT FACE="Times New Roman, serif">Obviously
    661. 

  661. the example is simple, but gives the idea of how the tasks could be
    662. 

  662. used to go through states.</FONT></P>
    663. 

  663. <P CLASS="western" STYLE="margin-bottom: 0in"><BR>
    664. 

  664. </P>
    665. 

  665. <P CLASS="western" STYLE="margin-bottom: 0in"><BR>
    666. 

  666. </P>
    667. 

  667. <P CLASS="western" STYLE="margin-bottom: 0in"><BR>
    668. 

  668. </P>
    669. 

  669. <OL START=3>
    670. 

  670. 	<LI><P CLASS="western" STYLE="margin-bottom: 0in"><FONT FACE="Times New Roman, serif"><B>MULTIPLE
    671. 

  671. 	POSSIBLE CALLBACKS FOR TASK</B></FONT></P>
    672. 

  672. </OL>
    673. 

  673. <P CLASS="western" STYLE="margin-bottom: 0in"><BR>
    674. 

  674. </P>
    675. 

  675. <P CLASS="western" STYLE="margin-bottom: 0in"><FONT FACE="Times New Roman, serif">There
    676. 

  676. may be a need to select an option for callback function based on
    677. 

  677. certain criteria, or randomly. </FONT>
    678. 

  678. </P>
    679. 

  679. <P CLASS="western" STYLE="margin-bottom: 0in"><FONT FACE="Times New Roman, serif">You
    680. 

  680. can achieve that by defining an array of callback function pointers
    681. 

  681. and selecting one based on the criteria you need. </FONT>
    682. 

  682. </P>
    683. 

  683. <P CLASS="western" STYLE="margin-bottom: 0in"><FONT FACE="Times New Roman, serif">Example:
    684. 

  684. when a robot detects an obstacle, it may go left, right backwards,
    685. 

  685. etc. Each of the “directions” or “behaviors” are represented
    686. 

  686. by a different callback function. </FONT>
    687. 

  687. </P>
    688. 

  688. <P CLASS="western" STYLE="margin-bottom: 0in"><BR>
    689. 

  689. </P>
    690. 

  690. <P CLASS="western" STYLE="margin-bottom: 0in"><FONT FACE="Times New Roman, serif">Another
    691. 

  691. example of using multiple callbacks:</FONT></P>
    692. 

  692. <P CLASS="western" STYLE="margin-bottom: 0in"><FONT FACE="Times New Roman, serif">You
    693. 

  693. may need to “initialize” variables for a particular task.</FONT></P>
    694. 

  694. <P CLASS="western" STYLE="margin-bottom: 0in"><FONT FACE="Times New Roman, serif">In
    695. 

  695. this case, define a tasks with two callbacks:</FONT></P>
    696. 

  696. <P CLASS="western" STYLE="margin-bottom: 0in"><BR>
    697. 

  697. </P>
    698. 

  698. <P CLASS="western" STYLE="margin-left: 0.49in; margin-bottom: 0in"><FONT FACE="Courier New, monospace"><FONT SIZE=2>Task
    699. 

  699. <B>tWork</B> (T_INTERVAL, -1, &amp;workCallbackInit);</FONT></FONT></P>
    700. 

  700. <P CLASS="western" STYLE="margin-left: 0.49in; margin-bottom: 0in">…</P>
    701. 

  701. <P CLASS="western" STYLE="margin-left: 0.49in; margin-bottom: 0in"><BR>
    702. 

  702. </P>
    703. 

  703. <P CLASS="western" STYLE="margin-left: 0.49in; margin-bottom: 0in"><FONT FACE="Courier New, monospace"><FONT SIZE=2>void
    704. 

  704.  workCallbackInit() {</FONT></FONT></P>
    705. 

  705. <P CLASS="western" STYLE="margin-left: 0.49in; margin-bottom: 0in"><FONT FACE="Courier New, monospace"><FONT SIZE=2>	//
    706. 

  706. do your initializationstuff here</FONT></FONT></P>
    707. 

  707. <P CLASS="western" STYLE="margin-left: 0.49in; margin-bottom: 0in"><FONT FACE="Courier New, monospace"><FONT SIZE=2>	</FONT></FONT></P>
    708. 

  708. <P CLASS="western" STYLE="margin-left: 0.49in; margin-bottom: 0in"><FONT FACE="Courier New, monospace"><FONT SIZE=2>	//
    709. 

  709. finally assigne the main callback function </FONT></FONT>
    710. 

  710. </P>
    711. 

  711. <P CLASS="western" STYLE="margin-left: 0.49in; margin-bottom: 0in"><FONT FACE="Courier New, monospace"><FONT SIZE=2>	tWork.setCallback(&amp;workCallback);</FONT></FONT></P>
    712. 

  712. <P CLASS="western" STYLE="margin-left: 0.49in; margin-bottom: 0in"><FONT FACE="Courier New, monospace"><FONT SIZE=2>}</FONT></FONT></P>
    713. 

  713. <P CLASS="western" STYLE="margin-left: 0.49in; margin-bottom: 0in"><BR>
    714. 

  714. </P>
    715. 

  715. <P CLASS="western" STYLE="margin-left: 0.49in; margin-bottom: 0in"><FONT FACE="Courier New, monospace"><FONT SIZE=2>void
    716. 

  716. workCallback() {</FONT></FONT></P>
    717. 

  717. <P CLASS="western" STYLE="margin-left: 0.49in; margin-bottom: 0in"><FONT FACE="Courier New, monospace"><FONT SIZE=2>	//
    718. 

  718. main callback function</FONT></FONT></P>
    719. 

  719. <P CLASS="western" STYLE="margin-left: 0.49in; margin-bottom: 0in"><FONT FACE="Courier New, monospace"><FONT SIZE=2>	…</FONT></FONT></P>
    720. 

  720. <P CLASS="western" STYLE="margin-left: 0.49in; margin-bottom: 0in"><FONT FACE="Courier New, monospace"><FONT SIZE=2>}</FONT></FONT></P>
    721. 

  721. <P CLASS="western" STYLE="margin-bottom: 0in"><BR>
    722. 

  722. </P>
    723. 

  723. <P CLASS="western" STYLE="margin-bottom: 0in"><FONT FACE="Times New Roman, serif">The
    724. 

  724. task will initialize during first execution pass and switch to
    725. 

  725. “regular” callback execution starting with second pass. There is
    726. 

  726. a delay between first and second passes of the task (scheduling
    727. 

  727. period, if defined). In order to execute the second pass immediately
    728. 

  728. after initialization first pass, change the above code like this:</FONT></P>
    729. 

  729. <P CLASS="western" STYLE="margin-bottom: 0in"><BR>
    730. 

  730. </P>
    731. 

  731. <P CLASS="western" STYLE="margin-left: 0.49in; margin-bottom: 0in"><FONT FACE="Courier New, monospace"><FONT SIZE=2>void
    732. 

  732.  workCallbackInit() {</FONT></FONT></P>
    733. 

  733. <P CLASS="western" STYLE="margin-left: 0.49in; margin-bottom: 0in"><FONT FACE="Courier New, monospace"><FONT SIZE=2>	//
    734. 

  734. do your initializationstuff here</FONT></FONT></P>
    735. 

  735. <P CLASS="western" STYLE="margin-left: 0.49in; margin-bottom: 0in"><FONT FACE="Courier New, monospace"><FONT SIZE=2>	</FONT></FONT></P>
    736. 

  736. <P CLASS="western" STYLE="margin-left: 0.49in; margin-bottom: 0in"><FONT FACE="Courier New, monospace"><FONT SIZE=2>	//
    737. 

  737. finally assigne the main callback function </FONT></FONT>
    738. 

  738. </P>
    739. 

  739. <P CLASS="western" STYLE="margin-left: 0.49in; margin-bottom: 0in"><FONT FACE="Courier New, monospace"><FONT SIZE=2>	tWork.setCallback(&amp;workCallback);</FONT></FONT></P>
    740. 

  740. <P CLASS="western" STYLE="margin-left: 0.49in; margin-bottom: 0in"><FONT FACE="Courier New, monospace"><FONT SIZE=2>	tWork.enable();</FONT></FONT></P>
    741. 

  741. <P CLASS="western" STYLE="margin-left: 0.49in; margin-bottom: 0in"><FONT FACE="Courier New, monospace"><FONT SIZE=2>}</FONT></FONT></P>
    742. 

  742. <P CLASS="western" STYLE="margin-bottom: 0in"><BR>
    743. 

  743. </P>
    744. 

  744. <P CLASS="western" STYLE="margin-bottom: 0in"><FONT FACE="Times New Roman, serif">The
    745. 

  745. task will run initialization first, then immediately second pass, and
    746. 

  746. then switch to processing at regular intervals starting with a third
    747. 

  747. pass. </FONT>
    748. 

  748. </P>
    749. 

  749. <P CLASS="western" STYLE="margin-bottom: 0in"><BR>
    750. 

  750. </P>
    751. 

  751. <OL START=3>
    752. 

  752. 	<LI><P CLASS="western" STYLE="margin-bottom: 0in"><FONT FACE="Times New Roman, serif"><B>INTERRUP-DRIVEN
    753. 

  753. 	EXECUTION SUPPORT </B></FONT>
    754. 

  754. 	</P>
    755. 

  755. </OL>
    756. 

  756. <P CLASS="western" STYLE="margin-bottom: 0in"><BR>
    757. 

  757. </P>
    758. 

  758. <P CLASS="western" STYLE="margin-bottom: 0in"><FONT FACE="Times New Roman, serif">In
    759. 

  759. case of interrupt-driven program flow, tasks could be scheduled to
    760. 

  760. run once to request asynchronous execution (request), and then
    761. 

  761. re-enabled (restarted) again with a different callback function to
    762. 

  762. process the results. </FONT>
    763. 

  763. </P>
    764. 

  764. <P CLASS="western" STYLE="margin-bottom: 0in"><BR>
    765. 

  765. </P>
    766. 

  766. <P CLASS="western" STYLE="margin-bottom: 0in"><FONT FACE="Times New Roman, serif"><B>Example</B>:
    767. 

  767. event driven distance calculation for ultrasonic pulses. EchoPin #6
    768. 

  768. triggers pin change interrupts on rising and falling edges to
    769. 

  769. determine the length of ultrasonic pulse.</FONT></P>
    770. 

  770. <P CLASS="western" STYLE="margin-bottom: 0in"><BR>
    771. 

  771. </P>
    772. 

  772. <P CLASS="western" STYLE="margin-left: 0.49in; margin-bottom: 0in"><FONT FACE="Courier New, monospace"><FONT SIZE=2>#include
    773. 

  773. &lt;DirectIO.h&gt;<BR>#include &lt;TaskScheduler.h&gt;<BR>#include
    774. 

  774. &lt;PinChangeInt.h&gt;<BR><BR><BR>#define  TRIGGERPIN 5<BR>#define 
    775. 

  775. ECHOPIN    6<BR><BR>Output&lt;TRIGGERPIN&gt; 
    776. 

  776. pTrigger;<BR>Input&lt;ECHOPIN&gt;      pEcho;<BR><BR>Scheduler
    777. 

  777. r;<BR><BR>Task  tMeasure(1000, -1, &amp;measureCallback);<BR>Task 
    778. 

  778. tDisplay(1000, -1, &amp;displayCallback);<BR>Task  tPing(0, 1,
    779. 

  779. &amp;pingCalcCallback);<BR><BR><BR>volatile bool pulseBusy =
    780. 

  780. false;<BR>volatile bool pulseTimeout = false;<BR>volatile unsigned
    781. 

  781. long pulseStart = 0;<BR>volatile unsigned long pulseStop =
    782. 

  782. 0;<BR>volatile unsigned long pingDistance = 0;<BR><BR><BR>void
    783. 

  783. pingTrigger(unsigned long aTimeout) {<BR>  if (pulseBusy) return;  //
    784. 

  784. do not trigger if in the middle of a pulse<BR>  if (pEcho == HIGH)
    785. 

  785. return; // do not trigger if ECHO pin is high<BR>  <BR>  pulseBusy =
    786. 

  786. true;<BR>  pulseTimeout = false;</FONT></FONT></P>
    787. 

  787. <P CLASS="western" STYLE="margin-left: 0.49in; margin-bottom: 0in"><FONT FACE="Courier New, monospace"><FONT SIZE=2><BR>
    788. 

  788.  pTrigger = LOW;<BR>  delayMicroseconds(4);<BR>  pTrigger = HIGH;<BR><BR>
    789. 

  789.  tPing.setInterval (aTimeout);<BR><BR>  delayMicroseconds(10);<BR> 
    790. 

  790. pTrigger = LOW; <BR></FONT></FONT><BR>
    791. 

  791. </P>
    792. 

  792. <P CLASS="western" STYLE="margin-left: 0.49in; margin-bottom: 0in"> 
    793. 

  793. <FONT FACE="Courier New, monospace"><FONT SIZE=2>tPing.restartDelayed();
    794. 

  794. // timeout countdown starts now<BR></FONT></FONT><BR>
    795. 

  795. </P>
    796. 

  796. <P CLASS="western" STYLE="margin-left: 0.49in; margin-bottom: 0in"><FONT FACE="Courier New, monospace"><FONT SIZE=2>//
    797. 

  797. will start the pulse clock on the rising edge of ECHO pin</FONT></FONT></P>
    798. 

  798. <P CLASS="western" STYLE="margin-left: 0.49in; margin-bottom: 0in"> 
    799. 

  799. <FONT FACE="Courier New, monospace"><FONT SIZE=2>PCintPort::attachInterrupt(ECHOPIN,
    800. 

  800. &amp;pingStartClock, RISING); <BR>}<BR><BR></FONT></FONT><BR>
    801. 

  801. </P>
    802. 

  802. <P CLASS="western" STYLE="margin-left: 0.49in; margin-bottom: 0in"><FONT FACE="Courier New, monospace"><FONT SIZE=2>//
    803. 

  803. Start clock on the <B>rising</B> edge of the ultrasonic pulse<BR>void
    804. 

  804. pingStartClock() {<BR>  pulseStart = micros();<BR> 
    805. 

  805. PCintPort::detachInterrupt(ECHOPIN); // not sure this is necessary<BR>
    806. 

  806.  PCintPort::attachInterrupt(ECHOPIN, &amp;pingStopClock, FALLING); <BR>
    807. 

  807.  tPing.restartDelayed();<BR>}<BR><BR>// Stop clock on the <B>falling</B>
    808. 

  808. edge of the ultrasonic pulse<BR>void pingStopClock() {<BR>  pulseStop
    809. 

  809. = micros();<BR>  PcintPort::detachInterrupt(ECHOPIN);</FONT></FONT></P>
    810. 

  810. <P CLASS="western" STYLE="margin-left: 0.49in; margin-bottom: 0in"> 
    811. 

  811. <FONT FACE="Courier New, monospace"><FONT SIZE=2>pingDistance =
    812. 

  812. pulseStop - pulseStart;<BR>  pulseBusy = false;<BR>  tPing.disable();
    813. 

  813. // disable timeout<BR>}<BR></FONT></FONT><BR>
    814. 

  814. </P>
    815. 

  815. <P CLASS="western" STYLE="margin-left: 0.49in; margin-bottom: 0in"><FONT FACE="Courier New, monospace"><FONT SIZE=2>//
    816. 

  816. Stop clock because of the timeout – the wave did not return<BR>void
    817. 

  817. pingCalcCallback() {<BR>  if (pulseBusy) {<BR>    pingStopClock();<BR>
    818. 

  818.  }<BR>  pulseTimeout = true;<BR>}<BR><BR><BR><BR>// Initial measure
    819. 

  819. callback sets the trigger<BR>void measureCallback() {<BR>  if
    820. 

  820. (pulseBusy) {  // already measuring, try again<BR>   
    821. 

  821. tMeasure.enable();<BR>    return;<BR>  }<BR>  pingTrigger(30); // 30
    822. 

  822. milliseconds or max range of ~5.1 meters<BR> 
    823. 

  823. tMeasure.setCallback(&amp;measureCallbackWait);<BR>}<BR></FONT></FONT><BR>
    824. 

  824. </P>
    825. 

  825. <P CLASS="western" STYLE="margin-left: 0.49in; margin-bottom: 0in"><FONT FACE="Courier New, monospace"><FONT SIZE=2>//
    826. 

  826. Wait for the measurement to <BR>void measureCallbackWait() {<BR>  if
    827. 

  827. (pulseBusy) return;<BR>  tMeasure.setCallback(&amp;measureCallback); 
    828. 

  828. <BR>}<BR><BR><BR>bool state = true;<BR><BR>void displayCallback() {<BR>
    829. 

  829.  char d[256];<BR>   <BR>  unsigned long cm = pingDistance * 17 / 100;
    830. 

  830. // cm<BR>  <BR>  snprintf(d, 256, &quot;pulseStart =
    831. 

  831. %8lu\tpulseStop=%8lu\tdistance, cm=%8lu&quot;, pulseStart, pulseStop,
    832. 

  832. cm);<BR>  Serial.println(d);<BR>  <BR>}<BR><BR>void setup() {<BR>  //
    833. 

  833. put your setup code here, to run once:<BR>  <BR> 
    834. 

  834. Serial.begin(115200);<BR>  <BR><BR>  pTrigger = LOW;<BR>  pEcho =
    835. 

  835. LOW;<BR>  <BR>  r.init();<BR>  r.addTask(tDisplay);<BR> 
    836. 

  836. r.addTask(tMeasure);<BR>  r.addTask(tPing);<BR>  <BR> 
    837. 

  837. r.enableAll();<BR>  tPing.disable();<BR>}<BR><BR>void loop() {<BR> 
    838. 

  838. // put your main code here, to run repeatedly:<BR>  r.execute();<BR>}<BR></FONT></FONT><BR>
    839. 

  839. </P>
    840. 

  840. </BODY>
    841. 

  841. </HTML>
    842.