WEBVTT 00:00.050 --> 00:05.570 Now that you have created your first circuit with an LED, let's control it with Python. 00:05.570 --> 00:11.270 If it's not done yet, you can power on your Raspberry Pi and just connect to it like you did before. 00:11.300 --> 00:13.340 For example, here I'm using VNC. 00:13.490 --> 00:17.930 Then you can open Thonny and we will write some Python code right here. 00:17.930 --> 00:24.530 And first of all we are going to include a Python module named Gpio zero. 00:24.530 --> 00:26.510 So Gpio zero. 00:26.540 --> 00:26.840 Okay. 00:26.870 --> 00:29.900 That's going to be the Python module that we want to import. 00:29.900 --> 00:34.940 So we can control the Gpio for the LED and how to import this module. 00:34.940 --> 00:40.160 Well previously you saw that we did that import time for example okay. 00:40.190 --> 00:43.640 Because time is a library that we wanted to use. 00:43.640 --> 00:44.900 We are also going to use it here. 00:44.900 --> 00:46.010 So I'm going to keep it here. 00:46.010 --> 00:48.860 You just write import and then the name of the library. 00:48.860 --> 00:52.430 Then we can add another import after that or even before that okay. 00:52.460 --> 00:54.320 The order doesn't really matter. 00:54.320 --> 00:58.700 And for example we could do import Gpio zero. 00:58.730 --> 01:06.000 Now the thing is when you do import library that's going to import the whole library with all the functionalities 01:06.000 --> 01:07.410 in this library. 01:07.410 --> 01:14.010 And as we will see with Python, sometimes it's better and we just want to import one specific functionality 01:14.040 --> 01:15.090 from the library. 01:15.090 --> 01:21.450 Because Gpio zero contains a lot of things for LEDs, push button and while many different devices. 01:21.450 --> 01:28.440 So if we want to just import for example the LED from Gpio zero, then we can just write. 01:28.440 --> 01:32.790 And notice here I used the word from we can just do from okay. 01:32.790 --> 01:36.630 This is a keyword from Gpio zero import. 01:36.630 --> 01:39.390 And then there's going to be led. 01:39.750 --> 01:44.640 So here we just import the LED because that's the only thing we need from that library okay. 01:44.640 --> 01:46.260 So that's kind of a good practice. 01:46.290 --> 01:52.050 And if you want to import several things from that library you can just add a comma and then put other 01:52.050 --> 01:53.040 functionalities. 01:53.160 --> 01:56.730 And let's just test that it works here I'm just going to run that. 01:56.730 --> 01:58.680 And you see we don't have any error. 01:58.710 --> 02:01.320 This means that it was found okay. 02:01.350 --> 02:04.770 So the Gpio zero is already installed for you. 02:04.800 --> 02:07.710 With Raspberry Pi OS you don't need to do anything. 02:07.710 --> 02:09.350 It's already installed and configured. 02:09.350 --> 02:09.680 Great. 02:09.680 --> 02:12.830 So now we can initialize our LED and how to do that. 02:12.860 --> 02:14.090 Well it's very simple. 02:14.090 --> 02:16.070 We're going to create a variable here. 02:16.250 --> 02:17.450 Let's call it LED. 02:17.450 --> 02:19.940 Lowercase is equal to. 02:19.970 --> 02:21.740 And then we're going to use the LED here. 02:21.740 --> 02:26.720 So uppercase LED we're going to open and close parentheses. 02:26.750 --> 02:30.680 And inside that we're going to need to put the Gpio number. 02:30.680 --> 02:35.390 So on the image you can see we used the Gpio number 17. 02:35.390 --> 02:37.670 So you just put 17 right here. 02:37.670 --> 02:39.800 And that's how you initialize an LED. 02:39.800 --> 02:42.650 So under the hood what it will do. 02:42.650 --> 02:48.800 And as you've seen in the previous lesson it will set the Gpio 17 as output. 02:48.800 --> 02:51.890 So then we can control it then how to control it. 02:51.890 --> 02:55.730 So how to say that we want the state to be high or to be low. 02:55.760 --> 02:57.500 Then you can do LED. 02:57.500 --> 03:03.230 So you can use this variable which in fact more technically is going to be an object. 03:03.260 --> 03:03.440 Okay. 03:03.470 --> 03:05.180 But I'm going to keep the word variable here. 03:05.180 --> 03:07.880 So you're going to use LED dot. 03:07.940 --> 03:12.970 And then you have a function inside the LED Uh, functionality here. 03:13.000 --> 03:16.270 LED Dot on to turn on the LED. 03:16.510 --> 03:17.860 It's quite simple. 03:17.860 --> 03:21.370 And as you call a function, you need to put some parentheses. 03:21.610 --> 03:25.570 Every time you call a function directly, you need to put the parentheses here. 03:25.570 --> 03:29.410 We don't have any argument to pass to the function okay. 03:29.440 --> 03:32.020 But we still need to give the parentheses. 03:32.020 --> 03:35.770 So LED on is going to turn on the LED. 03:35.770 --> 03:37.930 So it's going to set the state for the LED. 03:37.960 --> 03:41.530 So for the pin to high or 3.3V. 03:41.530 --> 03:45.370 And then you also have led dot off okay. 03:45.400 --> 03:47.050 So it's quite simple to understand. 03:47.080 --> 03:49.180 And this one is going to turn off the LED. 03:49.180 --> 03:55.420 So it's going to set the Gpio to low or basically close to zero volts okay. 03:55.420 --> 03:58.510 So what's going to happen if we run this program. 03:58.510 --> 04:04.600 What we will not see anything because you ask to turn on the LED and to turn it off right after it. 04:04.600 --> 04:08.440 So you will not see anything, or maybe just a very brief flash. 04:08.440 --> 04:15.140 So what we can do is we're going to use this time library here to do time dot sleep Clip. 04:15.590 --> 04:18.380 And then let's sleep for one second. 04:18.590 --> 04:18.800 Okay. 04:18.830 --> 04:20.390 So this we have used already. 04:20.420 --> 04:25.250 We're going to turn on the LED for one second and then turn off the LED. 04:25.250 --> 04:26.960 And that's the end of the program. 04:26.960 --> 04:30.980 So let's run this program and see what it's going to do. 04:30.980 --> 04:35.270 And you can see the LED is turned on for one second and then turn off. 04:35.270 --> 04:36.680 I can run the program again. 04:36.680 --> 04:40.220 So I click again and we have the same behavior. 04:40.250 --> 04:45.020 Now there is one thing I want to show you is, okay, let's say that we only have this line. 04:45.020 --> 04:46.340 So I'm going to comment. 04:46.460 --> 04:48.050 You see the comment is quite useful here. 04:48.050 --> 04:52.340 So I can comment it and then we can put the code back again later. 04:52.340 --> 04:56.180 So for now we just set the LED to on so to high. 04:56.180 --> 04:58.160 And let's see what's going to happen. 04:59.360 --> 05:06.650 And as you can see the LED is turned on and then it stays on okay the program has finished but the LED 05:06.650 --> 05:07.790 stays on. 05:07.790 --> 05:11.690 And you might think well it's quite obvious we didn't ask to turn it off. 05:11.690 --> 05:18.020 But actually in this Gpio zero there is a what is called a cleanup mechanism okay. 05:18.050 --> 05:24.480 Because when you finish your program, you want to basically reset all the pins to their default state 05:24.480 --> 05:25.650 and default mode. 05:25.650 --> 05:29.130 And basically the default mode for all the pins is input. 05:29.130 --> 05:35.490 And this is just a simple safety mechanism, because if you leave a pin as output and then let's say 05:35.490 --> 05:39.930 you plug a pushbutton in it, you might create a short circuit. 05:39.990 --> 05:41.700 So no need to worry about this for now. 05:41.700 --> 05:47.940 But you just need to know that if we run the code like this from thonny, the Gpio zero is not going 05:47.940 --> 05:49.230 to do the cleanup correctly. 05:49.230 --> 05:53.940 And I'm just talking about this now, because later on, we're going to actually use the terminal to 05:53.970 --> 05:55.110 run our programs. 05:55.110 --> 05:58.590 And when using the terminal we won't have this problem. 05:58.620 --> 05:58.860 Okay. 05:58.890 --> 06:01.260 So don't worry if you didn't really understand what I just said. 06:01.260 --> 06:07.200 Now it's going to make sense when we use the terminal and you're going to see the difference with what 06:07.200 --> 06:08.040 we did right now. 06:08.040 --> 06:09.600 So we have our LED on. 06:09.600 --> 06:11.940 I'm going to come back to this code LED on. 06:11.940 --> 06:14.700 We sleep for one second and then led off. 06:14.700 --> 06:22.080 Now what if you want to do this not just one time, but maybe two, three, five, ten times or even 06:22.110 --> 06:23.740 an infinite amount of time. 06:23.740 --> 06:27.580 Well, you're not going to repeat this code an infinite amount of time. 06:27.580 --> 06:29.320 You can use a loop. 06:29.320 --> 06:35.170 So for example, let's say that I want to simply do a infinite while loop. 06:35.170 --> 06:41.260 And I just want to say that when I start the program, the LED is going to blink until I stop the program, 06:41.260 --> 06:44.260 I can do while and then how to create an infinite loop. 06:44.260 --> 06:45.910 Well, I'm just going to put true. 06:45.940 --> 06:52.480 While true, so true is always going to be true, which means that we are always going to continue executing 06:52.480 --> 06:56.290 the loop until we here, until we press on the stop button. 06:56.290 --> 07:00.940 And so what I need to do here, you can see I have to put that with an extra indentation. 07:00.940 --> 07:06.250 So I select all the code and I press tab which means that this is going to be in the while loop. 07:06.250 --> 07:11.950 And it misses something because if you read the code what's going to happen with an on the LED? 07:11.980 --> 07:15.310 We wait for one second, then we turn off the LED. 07:15.550 --> 07:17.410 We go back and we turn on the LED. 07:17.710 --> 07:22.300 So we don't wait here before led off and led on. 07:22.300 --> 07:27.550 So if you run the code like this, you will see the LED D on all the time. 07:27.550 --> 07:33.190 Because there is there is no delay here between led off and LED on. 07:33.190 --> 07:38.950 So we need to add another time dot sleep with let's say one second as well. 07:39.190 --> 07:45.040 So it's going to turn on the LED, wait for one second and turn off the LED, wait for one second, 07:45.070 --> 07:50.980 etc. and let's run that program here okay. 07:50.980 --> 07:54.220 And you can see now the LED is blinking. 07:54.220 --> 08:00.100 And if I want to stop the program I can just click on stop here okay. 08:00.100 --> 08:03.730 So here I stopped and you can see it was off. 08:03.850 --> 08:06.880 But now let's run it again and let's stop it. 08:06.910 --> 08:13.480 Now you see I stop it when it's on and the LED stays on for the same reason as I told you before, because 08:13.480 --> 08:19.120 the Gpio zero is not cleaning up correctly here when we run the code from Thonny. 08:19.120 --> 08:23.770 But later on, as I told you before, everything is going to be fixed with the terminal. 08:23.770 --> 08:30.190 So you have learned how to control a LED with Python, and you can see with this Gpio library it's very 08:30.190 --> 08:30.910 easy to do.