WEBVTT 00:00.210 --> 00:06.810 Let's now face the problem that we had with the false information when we get the data from the ultrasonic 00:06.810 --> 00:12.960 sensor, because this function will take more or less time depending on the distance measured by the 00:12.960 --> 00:13.480 sensor. 00:14.040 --> 00:21.030 But if the distance is quite big, then this will really take a huge amount of time and that is not 00:21.030 --> 00:22.920 acceptable for the program. 00:23.190 --> 00:24.870 So here we are going to use interrupts. 00:25.080 --> 00:29.430 I'm going to explain to you first the principle and then we are going to write the code. 00:29.790 --> 00:32.000 Not that this is a little bit more advanced. 00:32.250 --> 00:37.180 We arrived at some point where it's really not but beginning to live it anymore. 00:37.500 --> 00:43.200 This isn't this specifically is a little bit more of an intermediate or advanced level. 00:43.560 --> 00:48.540 But I guess you should be fine because you have already seen and practiced with everything you need 00:48.540 --> 00:50.250 to know to understand this. 00:50.610 --> 00:52.630 So first, let's see how to solve the problem. 00:53.930 --> 01:01.900 So here is the classic place in that we have seen so far, so you goldbugs in that is the first thing, 01:01.910 --> 01:08.570 then we wait, OK, as long as the signal is low and then the signal goes to high. 01:08.600 --> 01:14.540 So this is the pulsing with the high mode both in we start measuring and then when the signal goes to 01:14.540 --> 01:18.620 localising, we stop measuring and return the pulse duration. 01:19.130 --> 01:24.320 So between them, the number one and number four, everything here will block your program. 01:24.890 --> 01:31.760 So if, for example, the wait here is the signal stays low for a long time, well, that's more time 01:31.760 --> 01:32.750 to plug the program. 01:32.960 --> 01:35.600 And then the longer the pulse, the longer the pulse. 01:35.600 --> 01:37.600 It will take time to measure the pulse. 01:37.610 --> 01:39.160 And also we block your program. 01:39.410 --> 01:46.060 So our sensor, if you have a greater distance, this will be bigger and then you will wait more. 01:46.310 --> 01:50.040 So you have two times here where you are just going to wait. 01:50.060 --> 01:52.610 And the thing is that you actually just need two things. 01:52.610 --> 01:58.850 You need to start measuring this point here and measure this point here and make the difference so the 01:58.850 --> 02:02.300 person does the job OK, does the job already correctly. 02:02.300 --> 02:09.200 We have the correct value every time, but the time between the point one, point four is really too 02:09.200 --> 02:10.880 much can really be too much. 02:11.240 --> 02:18.110 So what we're going to do, we are going to do the same thing, which is basically to measure this duration, 02:18.530 --> 02:21.530 but using interrupts and how are we going to do this? 02:21.750 --> 02:23.420 So here is the person. 02:24.260 --> 02:27.200 We are going to do this in three steps. 02:27.740 --> 02:29.620 The first step we're going to set. 02:29.640 --> 02:37.580 So an interrupt when the signal changes and then when the signal goes from low to high, we are going 02:37.580 --> 02:39.170 simply to get the time. 02:39.350 --> 02:41.840 We are going to store the time in global view. 02:42.110 --> 02:48.560 So, for example, time begins and then when our program continues to execute and we have another interruptive 02:49.100 --> 02:52.000 OK, using still the change mode. 02:52.010 --> 02:55.460 So the change is the rising mode and the following mode. 02:55.760 --> 03:00.140 So when the signal is falling, we are simply going to also get the time. 03:00.860 --> 03:04.270 So we get the time at the beginning, we get the time at the end. 03:04.490 --> 03:07.970 And then here we set a flyer, we set the global flag. 03:08.300 --> 03:11.140 And the third step is, look what we do. 03:11.150 --> 03:12.920 We simply check for that flag. 03:13.370 --> 03:17.000 And then once we have this flag, we compute the distance. 03:17.150 --> 03:18.590 How do we conclude the distance? 03:18.780 --> 03:21.580 Well, we have the time and we have the time begin. 03:21.860 --> 03:24.010 We do timing minus time being. 03:24.440 --> 03:31.760 This gives us the duration of the inputs and from the duration we have the formula to convert this into 03:31.910 --> 03:32.630 a distance. 03:33.530 --> 03:36.140 So that's actually pretty simple. 03:36.650 --> 03:41.300 And the program is not blocked anymore because here you still continue the execution. 03:41.540 --> 03:43.220 You just have to interrupt. 03:43.940 --> 03:47.060 That is fired twice where you simply get the time. 03:47.070 --> 03:51.020 So this is very quick and then you simply take a flag inside the envelope. 03:51.020 --> 03:53.380 So this will take almost no time. 03:54.630 --> 04:00.270 And back to the code, let's just use the Internet, just like I have explained with the diagram. 04:00.630 --> 04:06.330 So I'm going to start by setting up the interrupt on the equal number three. 04:06.510 --> 04:07.750 And again, this is important. 04:07.800 --> 04:12.300 Make sure that the equipment is connected on an interactive podiatric. 04:13.080 --> 04:20.510 So I'm going to create a function here that's that's void because this is an indirect we don't have 04:20.510 --> 04:21.030 the choice. 04:21.540 --> 04:24.810 Let's call it equal to interrupt. 04:27.220 --> 04:33.660 And no parameter because we don't have the choice either voit no idea what I'm going to do. 04:33.670 --> 04:41.140 I'm going to do a Dutch interrupt with digital bean to. 04:42.390 --> 04:46.240 Internet and digital ping is the echo here. 04:47.370 --> 04:55.640 OK, I appreciate Cooma, I press enter, just make it nicer to read, so the function here, AECO been 04:55.650 --> 04:56.170 interrupted. 04:57.220 --> 05:04.240 And then the mode, so the mode we need, the mode is change, OK, because we need to know when the 05:04.240 --> 05:10.390 signal is arising, which is going from low to high and when the signal is falling, which is going 05:10.390 --> 05:14.620 from high to low and change will give us both. 05:14.920 --> 05:22.510 So now that we have done that, this will be triggered every time we have a change in the ECOFIN signal. 05:22.960 --> 05:28.990 And now when we are in this interrupt, when actually because this is a change mode, we don't necessarily 05:28.990 --> 05:33.870 know if the signal is rising or if the snow is falling. 05:34.150 --> 05:39.620 So because of this, when you use change, you need to check again the signal. 05:39.640 --> 05:44.770 So if digital read Iku in. 05:45.830 --> 05:58.460 Is I OK and then to do something else, so if the signal is low, but if you use the following mode, 05:58.460 --> 06:01.370 you know the signal is low because it's going to low. 06:01.580 --> 06:04.340 If you use the rising mode, you know, the signal is high. 06:04.760 --> 06:09.620 But if you use change, you just know that the signal went from low to high or high to low, but you 06:09.620 --> 06:10.620 don't know which one. 06:10.940 --> 06:12.870 So you need to check with digital radio. 06:13.310 --> 06:18.380 OK, so usually when I've told you is to discourage you to use digital right. 06:18.380 --> 06:23.330 Or other functions in the interactivity, you don't have the choice you need to use digital, which 06:23.330 --> 06:25.010 will be quite fast. 06:25.640 --> 06:29.730 So here we know the signal has changed and we've high. 06:29.760 --> 06:31.610 We know the signal is rising. 06:33.240 --> 06:42.160 And as the signal is falling, the when the signal is rising, what do we do when we start measuring 06:42.160 --> 06:47.250 it and when the signal is fully, we would stop measuring. 06:47.940 --> 06:49.530 So how do we start measuring? 06:49.590 --> 06:53.610 Well, we are going to create two new variables here. 06:57.350 --> 06:59.030 Unsigned, long. 07:00.130 --> 07:01.030 Both in. 07:02.610 --> 07:03.840 Time Biggart. 07:06.140 --> 07:10.960 Can not going to put any value in this because we are going to initialize them or just said the value 07:10.970 --> 07:18.680 directly in the Internet and then unsigned long just in time. 07:18.960 --> 07:25.910 And so I just named it both in time being OK, because this is the time when the police in Beijing, 07:25.910 --> 07:32.660 basically when the signal goes to I in here, when the signal goes to low end because we are going to 07:32.660 --> 07:38.830 modify them inside the interrupts, I'm going to put volatile it and also keep. 07:41.540 --> 07:44.900 So not what we do is quite simple, we do. 07:46.220 --> 07:50.150 I'm going to take place in time. 07:51.220 --> 07:53.200 Begin is equal to. 07:54.810 --> 07:55.400 Microbes. 07:55.590 --> 08:01.880 OK, I use microbes because we have the pulse in function, we were getting a duration in microseconds, 08:02.070 --> 08:03.300 so I'm going to keep that. 08:03.300 --> 08:06.210 I'm going to also consider duration in microseconds. 08:06.570 --> 08:15.860 And then when the signal is falling, we do those in time and which is equal to microbes. 08:16.530 --> 08:22.570 So we have stored the two times that are important, which is when the signal went high. 08:23.040 --> 08:27.120 So when the pulse begins and when the signal went low. 08:27.150 --> 08:30.750 So when the pulse ends, I know how to conclude this. 08:30.960 --> 08:38.790 Well, I'm going to add in a new thing, which is I'm going to create so volatile. 08:41.420 --> 08:43.220 Bu new. 08:44.590 --> 08:45.250 Dist.. 08:47.100 --> 08:47.740 Available. 08:48.880 --> 08:54.630 And let's initialize this to faults, so I'm going to create a boolean, which I can also call flag, 08:54.670 --> 08:57.530 can be volatile, new distance available. 08:58.240 --> 08:59.700 So this is false. 08:59.890 --> 09:04.230 And here when we stop, the measurement are when we just get the time. 09:04.540 --> 09:07.120 In the end, I'm going to do so. 09:07.150 --> 09:08.290 The name is new. 09:10.310 --> 09:14.030 Distance available is true. 09:14.780 --> 09:19.970 OK, so just with the interrupt running, so we have to interrupt, just with the interrupt running, 09:19.970 --> 09:27.320 we will automatically get the three variables updated with the time, but the beginning of the birth, 09:27.330 --> 09:32.780 the time for the end of the post and when also we update this, we update this boolean to true. 09:33.350 --> 09:37.460 So now what we need to do is to check in the loop for this billion. 09:38.270 --> 09:39.870 So I'm going to run that line here. 09:40.970 --> 09:43.760 We're not going to get the distance in this. 09:44.180 --> 09:52.220 We are going simply to keep this structure here to simply trigger the ultrasonic sensor every 100 million 09:52.970 --> 09:53.690 signal here. 09:55.740 --> 09:59.280 But we are simply going to tringale and then I'm going to do if. 10:00.450 --> 10:00.840 New. 10:02.230 --> 10:04.320 Distance available. 10:05.650 --> 10:09.560 So is the flag that we have set in the interrupt is true. 10:10.120 --> 10:12.760 So what I'm going to do is first say to false. 10:16.730 --> 10:23.570 So we do not enter this another time, we enter this only another time, if we have also put the flag 10:23.570 --> 10:28.350 to true again in the interim, and then I do the action and the action is. 10:28.370 --> 10:35.600 So let's say double distance is equal to get ultrasonics. 10:37.310 --> 10:44.960 Distance and I'm going also to modify the jet ultrasonic distance, so to get the duration of the pulse 10:44.960 --> 10:46.050 in microseconds. 10:46.400 --> 10:49.930 Now I'm going to remove the person we are not going to use in. 10:50.150 --> 10:55.320 I'm simply going to compute the duration with the time that we already got in the program. 10:55.640 --> 11:04.910 So both in time and minus, but in time begin and. 11:04.910 --> 11:05.980 Well, that's it. 11:06.800 --> 11:12.440 Will this we get the duration of the birds and then when the competition is exactly the same. 11:12.950 --> 11:14.900 OK, so we get the distance. 11:14.900 --> 11:21.080 So I could just print these, but I'm going to do to get violent and do sale of prints. 11:21.110 --> 11:21.620 Ellen. 11:22.860 --> 11:32.340 With the distance, let's actually verify the code, so I have a trussoni project, not the activity, 11:32.730 --> 11:34.590 and let's upload the code. 11:35.010 --> 11:36.200 Let's see if it works. 11:37.960 --> 11:45.250 And let's open the science monitor and you can see here, well, we have the exact same values as we 11:45.250 --> 11:45.830 had before. 11:45.850 --> 11:49.020 So the functionality, I'm going to put my hand closer, OK? 11:49.060 --> 11:52.530 You can see the functionality is exactly the same as before. 11:52.930 --> 11:57.460 But no, we are not stuck with the bills in function. 11:57.850 --> 12:05.770 So to quickly recap, when I do the setup, I also attach and interrupt or coping with the change mode. 12:06.230 --> 12:13.320 OK, then in the loop, what I do is every one hundred milliseconds I trigger the ultrasonic sensor, 12:13.330 --> 12:21.010 so I send you a high signal for 10 microseconds and then they exit and then, well, the program can 12:21.010 --> 12:24.600 continue and then everything will happen in the background. 12:24.610 --> 12:30.390 So the ultrasonic sensor will send back some data on the equipping. 12:30.670 --> 12:32.730 And what we need to do is to measure the pulse. 12:33.040 --> 12:38.310 So we have the interrupt, which will be triggered when the signal is rising. 12:38.650 --> 12:41.470 This time we initialize the pulse in time. 12:41.470 --> 12:46.420 Begin with the time right now when the interrupt is fired and then interrupt exits. 12:46.750 --> 12:52.010 So the program continues to execute with all the other actions in the code. 12:52.030 --> 12:53.400 OK, no problem with that. 12:53.830 --> 13:00.520 And then when the signal on the equipment goes to low, well, we also have the trigger of this interrupt 13:00.520 --> 13:01.060 the same. 13:01.570 --> 13:07.050 And now we know that we need to update the time and OK and set the flag to true. 13:07.810 --> 13:10.900 So then what happens is in the loop function. 13:11.260 --> 13:12.640 We can check the fly. 13:12.700 --> 13:17.470 OK, so we take the flag and when this is true, well, so we set it to faults of course. 13:17.830 --> 13:25.750 And well we can do the functionality which is get the distance and we get the distance simply by subtracting 13:25.750 --> 13:33.070 the time and the time beginning that we have set in to interrupt and then when we complete the distance 13:33.070 --> 13:35.930 from the duration of this computation. 13:36.280 --> 13:42.130 So this call now is pretty good, pretty efficient, and we are not stuck any time in the program. 13:42.640 --> 13:48.910 Note again that here the delay microseconds are so small compared to what we had here. 13:49.390 --> 13:50.830 It's ten microseconds. 13:51.210 --> 13:55.460 It was more about twenty five thousand microseconds. 13:55.480 --> 14:01.330 OK, so depending on the number, if it's a very small number like this, you can use it in your code 14:01.330 --> 14:02.530 with the microseconds. 14:02.530 --> 14:04.610 If it's too big, then it's better to avoid it. 14:04.990 --> 14:09.360 And one thing to note here is that frequency here. 14:09.370 --> 14:12.130 So we have every one hundred milliseconds. 14:12.850 --> 14:16.360 It's best to keep a minimum of 60. 14:16.370 --> 14:19.540 OK, this is recommended for these components. 14:19.930 --> 14:25.900 Were having to put one hundred, but tried to use 60 and not below 60. 14:25.910 --> 14:29.320 OK, this is recommended by the supplier of the component. 14:29.590 --> 14:32.110 And also if you go to low with this value, let's say you. 14:32.120 --> 14:40.600 But then when the thing is that you are going to trigger the trigger being very, very fast and then 14:40.600 --> 14:45.820 the sensor will not be able to keep up with the data to send on the A.P. and the data you will receive 14:46.030 --> 14:48.640 interest might be not correct. 14:48.850 --> 14:51.510 OK, so 100 is good. 14:51.700 --> 14:57.510 Try to go at least 60 or 100 or more and everything will be fine with this program.