1 00:00:00,610 --> 00:00:01,760 Hello, welcome back. 2 00:00:01,780 --> 00:00:09,670 In this lesson, we're going to see how to synchronize multiple tasks using event groups have gone ahead 3 00:00:09,670 --> 00:00:15,080 to create a new project or make a copy of a previous project and then clean it up. 4 00:00:15,640 --> 00:00:20,700 I gave this the name Sinkin Tasks, which events groups number 30 over here. 5 00:00:21,220 --> 00:00:25,840 OK, so we can just start we start off by defining the bits for our tasks. 6 00:00:26,110 --> 00:00:32,320 We're going to have three of them like we did earlier, task one, task two and task three. 7 00:00:32,470 --> 00:00:34,570 Each of them have bits, OK? 8 00:00:35,050 --> 00:00:37,690 And what we're going to do is we go into. 9 00:00:39,680 --> 00:00:42,440 We're going to declare the 104 event group. 10 00:00:46,430 --> 00:00:54,530 OK, and then once that is done, we are going to declare the event bids for all the tasks combined. 11 00:00:55,100 --> 00:01:02,450 OK, if we combine all the tasks, all the task bit, if we combine task one, which task to bit, task 12 00:01:02,450 --> 00:01:05,420 three bit, we storage in a variable called all sink bits. 13 00:01:05,730 --> 00:01:06,830 These are all the bits. 14 00:01:07,370 --> 00:01:14,810 OK, once that is done, we come to our main function and we create a what event group. 15 00:01:16,160 --> 00:01:22,100 So come over here and our great defense group, once I've done that, I'm going to create the tasks 16 00:01:22,310 --> 00:01:25,120 I've created three of them, task one, two and three. 17 00:01:26,210 --> 00:01:28,790 They all have the same priority and. 18 00:01:29,720 --> 00:01:38,730 The same stuck sighs Once this is done, I'm going to start the shetler by calling the X starts chuch 19 00:01:38,750 --> 00:01:41,660 the next task, search that function. 20 00:01:42,380 --> 00:01:46,490 OK, so once this is done, we go ahead and. 21 00:01:48,010 --> 00:01:55,360 We create the task functions, so I'm going to start off with task one, that's a standard task function 22 00:01:55,360 --> 00:01:57,310 over here and over here. 23 00:01:57,310 --> 00:02:05,110 We're going to have a local variable here to store the the return because we're going to read the events 24 00:02:05,410 --> 00:02:08,680 that will be returned and then in our infinite loop. 25 00:02:10,070 --> 00:02:13,880 We going to see one over here. 26 00:02:17,580 --> 00:02:20,700 And then we use the function events group Sync. 27 00:02:22,110 --> 00:02:22,560 Right. 28 00:02:22,590 --> 00:02:24,510 So if any group sanchia. 29 00:02:28,640 --> 00:02:34,790 So this function, as we can see, takes four arguments, the first argument is the handle of the event 30 00:02:34,790 --> 00:02:35,220 group. 31 00:02:35,720 --> 00:02:38,190 The second argument is the bits to set. 32 00:02:38,720 --> 00:02:44,390 So the idea is that each task would set its bit and then wait for the rest of the bit. 33 00:02:44,780 --> 00:02:47,350 So task one would set the task one bit. 34 00:02:47,690 --> 00:02:51,920 And then the third argument is the bits to wait for. 35 00:02:51,920 --> 00:02:57,530 So task one will wait for all the bits, in our view, X or sing bits to be set. 36 00:02:58,010 --> 00:02:59,510 This one that has all of our bits. 37 00:02:59,870 --> 00:03:03,350 So task one will set it to bits and wait for all the bits. 38 00:03:03,530 --> 00:03:05,470 And over here we are giving Portsmouth's delay. 39 00:03:05,660 --> 00:03:06,170 OK. 40 00:03:07,120 --> 00:03:14,110 Right, so once that is done, we would proceed, we wait for all the bids and we'll be stuck here and 41 00:03:14,110 --> 00:03:17,590 then until all the bids are set, then we'll proceed. 42 00:03:18,710 --> 00:03:25,150 So then we can use on if condition to check whether all the bits are set. 43 00:03:25,180 --> 00:03:31,900 So we come over here and we see if what is returned, which is our you x return and all bids Singh bids 44 00:03:31,900 --> 00:03:39,430 equals all being bids, meaning all of them said, then we can do something here. 45 00:03:41,420 --> 00:03:45,840 So basically, all of the tasks are synched, right? 46 00:03:45,980 --> 00:03:52,700 So this is going to be the same code for all of the other task, just that they will set their own bit 47 00:03:52,820 --> 00:03:53,510 and check. 48 00:03:54,410 --> 00:03:54,980 OK. 49 00:03:57,100 --> 00:03:59,950 So what I'm going to do is I'm going to make a copy of this. 50 00:04:01,200 --> 00:04:02,590 Going to make a copy of this. 51 00:04:06,100 --> 00:04:14,110 And call this task to an over here task to here will set its bit task, too, and wait for the rest. 52 00:04:15,970 --> 00:04:22,100 The same for TASC three, TASC three was set, it's a bit ago, this task three. 53 00:04:22,120 --> 00:04:28,210 First, it would set its bit and wait for the rest, but over here we can take the opportunity to print 54 00:04:28,210 --> 00:04:28,660 something. 55 00:04:29,020 --> 00:04:34,470 And the reason I don't want all of them to print something is because our UAT is a single resource. 56 00:04:34,480 --> 00:04:36,400 It requires exclusive access. 57 00:04:36,730 --> 00:04:44,590 If all the three task, they are synchronized, meaning they all execute what is in the if block at 58 00:04:44,590 --> 00:04:45,700 almost the same time. 59 00:04:45,850 --> 00:04:51,270 So if all of them are trying to print that, you are at almost the same time we know what would happen. 60 00:04:51,280 --> 00:04:53,470 We saw that in our semaphores experiment. 61 00:04:54,100 --> 00:04:55,060 So over here. 62 00:04:55,980 --> 00:04:57,720 I can print all task. 63 00:04:59,940 --> 00:05:00,450 Set. 64 00:05:03,810 --> 00:05:07,800 OK, and we'll find a controlled experiment to show what happens if this is not the case. 65 00:05:08,280 --> 00:05:08,730 OK. 66 00:05:11,980 --> 00:05:18,340 And what we have to do now is take the function prototypes to the top of the file, a copy task, one 67 00:05:18,340 --> 00:05:24,790 over here, and I'll drop this over here and then task to over here. 68 00:05:27,770 --> 00:05:30,940 And we have task number three as well. 69 00:05:33,440 --> 00:05:34,060 OK. 70 00:05:35,710 --> 00:05:36,780 And, um. 71 00:05:40,300 --> 00:05:40,810 Right. 72 00:05:40,840 --> 00:05:44,260 So let's see what we have we can click to build. 73 00:05:45,930 --> 00:05:47,340 I'll click over here to build. 74 00:05:51,700 --> 00:05:53,170 It's built successfully. 75 00:05:55,030 --> 00:05:57,190 And I'm going to right click over here. 76 00:05:58,110 --> 00:06:01,050 And go to the blog, US, ASTM 30 to. 77 00:06:02,170 --> 00:06:03,790 A select number 30. 78 00:06:05,640 --> 00:06:07,500 And then they'll say, OK, over here. 79 00:06:14,450 --> 00:06:15,680 And then I'll click to switch. 80 00:06:19,550 --> 00:06:22,970 This old project, I'm going to clean what we have over here. 81 00:06:23,000 --> 00:06:23,510 Claire. 82 00:06:29,050 --> 00:06:32,910 And then I'm going to open up several ports of barge trigger. 83 00:06:35,590 --> 00:06:37,630 This and I'll click to. 84 00:06:43,500 --> 00:06:44,790 All task set. 85 00:06:46,030 --> 00:06:46,480 Right. 86 00:06:47,090 --> 00:06:47,520 OK. 87 00:06:48,630 --> 00:06:51,330 So we were able to get all tasks set. 88 00:06:55,270 --> 00:06:55,840 Switch. 89 00:06:56,720 --> 00:07:00,380 I press this instead terminates and relaunch. 90 00:07:00,410 --> 00:07:04,010 That is why we've seen this works, but I want us to. 91 00:07:04,920 --> 00:07:08,070 Run this again, Cledus, and then Pressplay. 92 00:07:15,030 --> 00:07:16,100 It's rather strange. 93 00:07:16,380 --> 00:07:17,310 Let's stop and see. 94 00:07:21,150 --> 00:07:23,400 Events, bits, so let's stop this. 95 00:07:25,550 --> 00:07:26,600 And then, um. 96 00:07:28,830 --> 00:07:31,080 My computer is Lodin. 97 00:07:32,190 --> 00:07:33,270 Why do we have this? 98 00:07:35,310 --> 00:07:36,930 OK, real time is frozen. 99 00:07:39,000 --> 00:07:45,550 I'm going to add a bit of delay when we print to slow down and stabilize the print in a bit. 100 00:07:45,990 --> 00:07:47,010 So over here. 101 00:07:48,380 --> 00:07:54,370 I'm going to say delay for this amount and I'm going to add new line carriage return as well. 102 00:07:56,960 --> 00:07:59,420 OK, I'm going to click here to build. 103 00:08:09,590 --> 00:08:12,350 I see it build successfully as go to debugger. 104 00:08:17,200 --> 00:08:18,250 A click to switch. 105 00:08:23,110 --> 00:08:29,760 OK, I'll come over here, new line mode selector about right over here. 106 00:08:31,480 --> 00:08:33,640 And then select our ports over here. 107 00:08:36,960 --> 00:08:37,500 And then. 108 00:08:38,310 --> 00:08:44,490 I'll click to Open and I'll click to run over here, is going to see all tasks set. 109 00:08:44,840 --> 00:08:48,780 OK, so we are receiving all this. 110 00:08:48,780 --> 00:08:49,320 Looks good. 111 00:08:51,090 --> 00:08:53,550 So we've essentially synchronized the tasks. 112 00:08:57,750 --> 00:09:04,920 One way you can check this also is to have if you could if you can enable three LEDs, if you have the 113 00:09:04,920 --> 00:09:09,530 discovery board, you can enable three LEDs and place each of them in the tasks. 114 00:09:09,960 --> 00:09:17,790 And you could see the LED lights on when the when we reach here, the do something could simply be turning 115 00:09:17,790 --> 00:09:18,090 on on. 116 00:09:18,780 --> 00:09:22,410 And you should see all LEDs come on at once at the same time. 117 00:09:23,010 --> 00:09:23,550 OK. 118 00:09:25,510 --> 00:09:32,430 OK, so what is the controlled experiment, how do we know it is really sinking here and not just printing? 119 00:09:32,830 --> 00:09:40,150 OK, remember we said each task here, this function inherently makes the second argument. 120 00:09:40,150 --> 00:09:48,400 GetSet What I mean by this is when we call X Events group sync and we pass Task one Bethia, this sets 121 00:09:48,610 --> 00:09:50,240 the bits for task one bit. 122 00:09:50,440 --> 00:09:51,450 This sets this bit. 123 00:09:52,450 --> 00:09:58,000 So how we come into one of them and see if indeed we still have our message print. 124 00:09:58,360 --> 00:10:03,230 Right, because the idea is when we comment one of them task, one bit won't be set. 125 00:10:03,250 --> 00:10:07,820 So when we get here where the message is printed, it's waiting for all the bits. 126 00:10:08,410 --> 00:10:10,260 So we expect that task. 127 00:10:10,300 --> 00:10:11,320 One bit is not set. 128 00:10:11,320 --> 00:10:14,050 So waiting for all the bits should wait forever. 129 00:10:14,590 --> 00:10:21,280 So what I'm going to do is I'm going to highlight this and control to comment this out and I'm going 130 00:10:21,280 --> 00:10:22,240 to click here to build. 131 00:10:26,920 --> 00:10:31,900 It's built successfully, the one in is because we're not using this variable, but this is a controlled 132 00:10:31,900 --> 00:10:34,930 experiment, so we know that we click here. 133 00:10:40,450 --> 00:10:42,460 To go to debugger, click to switch. 134 00:10:46,490 --> 00:10:47,120 OK. 135 00:10:50,020 --> 00:10:51,220 So let's run. 136 00:10:51,250 --> 00:10:56,480 I'm going to press play over here, and as you can see, we have this system initializing. 137 00:10:56,860 --> 00:10:58,060 We've printed just this. 138 00:10:58,690 --> 00:11:02,230 And what is happening is that over here, they are all waiting. 139 00:11:03,290 --> 00:11:10,220 Task to task three, they are waiting for all the bits of bits to be synchronized, remember, all bits 140 00:11:10,220 --> 00:11:15,620 sink, they are waiting for all bits to be set and we know one of them is commented out, so we would 141 00:11:15,620 --> 00:11:16,430 never guess it. 142 00:11:16,640 --> 00:11:18,140 So we'll never have this printed. 143 00:11:18,320 --> 00:11:22,320 So this is what proves that indeed synchronisation is what is going on. 144 00:11:23,140 --> 00:11:27,170 OK, so we can comment what we've commented out. 145 00:11:29,880 --> 00:11:30,540 Over here. 146 00:11:34,960 --> 00:11:35,410 Right. 147 00:11:35,620 --> 00:11:41,020 So this is it, this is it for synchronizing tasks, using event groups. 148 00:11:41,290 --> 00:11:42,500 I'll see you the next lesson. 149 00:11:42,520 --> 00:11:43,330 Have a nice day.