WEBVTT 00:00.080 --> 00:05.870 This is the solution of the first activity of this course where you have to power on or power off an 00:06.140 --> 00:10.400 on the Arduino from a user input you get from the Raspberry Pi. 00:10.400 --> 00:11.600 And let's get started. 00:11.600 --> 00:20.360 So I have created a new project file in Python here on Thonny Python and also a new project on Arduino. 00:20.390 --> 00:23.300 Okay, so start from a blank page. 00:23.300 --> 00:29.270 Now, the first thing before we even start to write some code is to define the protocol. 00:29.270 --> 00:34.520 So I've already done that actually for you in the first activity, but I'm going to talk about that 00:34.520 --> 00:36.260 just a few more seconds. 00:36.290 --> 00:36.830 Okay. 00:37.250 --> 00:43.610 So as you can see, it's super important to know in advance what data you are going to send and receive 00:43.610 --> 00:44.870 from both sides. 00:44.900 --> 00:45.500 Okay. 00:45.740 --> 00:54.410 As you can see here, with on and off, we send that and we receive that if we don't agree on both sides, 00:54.410 --> 00:58.370 okay, to send the same data, then we are going to have some problems. 00:58.400 --> 00:58.670 Okay. 00:58.670 --> 01:04.240 Think about what data you need to send and receive and then write this in advance in, for example, 01:04.240 --> 01:06.320 a text document or in a comment. 01:06.330 --> 01:11.940 This is the protocol you're going to use, and for each application you are going to do well. 01:11.940 --> 01:15.930 You are going to define a custom protocol before you write any code. 01:16.080 --> 01:16.260 Okay. 01:16.260 --> 01:21.000 Let's say, for example, here, I wanted to send an Led on an Led off. 01:21.000 --> 01:28.470 Well, if I send this and if I try to read on, well, you can see that if I send led on, I'm not going 01:28.470 --> 01:32.850 to be able to detect on because this is not the same string. 01:32.880 --> 01:33.060 Okay. 01:33.060 --> 01:38.610 So I need to make sure that I send something that is the same on both sides. 01:38.970 --> 01:39.420 All right. 01:39.420 --> 01:42.630 So now let's start with the Arduino code. 01:42.750 --> 01:42.960 Okay. 01:42.960 --> 01:47.640 So once again, we start from Arduino because that's simply easier to debug. 01:47.640 --> 01:47.820 Okay. 01:47.820 --> 01:53.430 We can start with this code, debug it with the monitor, make sure that the communication is correctly 01:53.430 --> 01:58.680 working on that side and then we can create the other side. 01:58.830 --> 02:01.980 So here we have two things to do. 02:02.010 --> 02:06.060 We have to set up the Led and we have to set up the communication. 02:06.060 --> 02:08.040 I'm going to start with the Led. 02:08.070 --> 02:08.280 Okay. 02:08.280 --> 02:13.140 So we first start with the Led and then we use the serial and from the side we can directly make the 02:13.170 --> 02:17.070 Led blink so that we can check that the serial is correctly working. 02:17.070 --> 02:23.700 So let's create a define Led PIN 13 for the Led. 02:23.700 --> 02:31.590 And then in the setup I am going to do pin mode led pin output. 02:32.550 --> 02:35.160 All right, So we have a define. 02:35.160 --> 02:37.590 We have set output mode for the Led. 02:37.590 --> 02:41.970 So now we can do digitalwrite on the Led with high or low. 02:41.970 --> 02:46.170 And so well, when are we going to do digitalwrite with high and low? 02:46.200 --> 02:49.860 We are going to do that when we receive some data from the cell. 02:49.860 --> 02:55.920 So in the while loop, what I'm going to do is I'm going to read from Serial, but before I'm going 02:55.920 --> 03:02.790 to of course, initialize Serial with Begin, let's use this baud rate, okay? 03:02.790 --> 03:09.690 And let's do while on serial like this with exclamation mark. 03:11.580 --> 03:13.740 So not needed on Arduino Uno. 03:13.740 --> 03:18.540 But for example, if you have a Leonardo or a zero board, well, you're going to need that. 03:18.540 --> 03:20.100 So I'm going to put that anyway. 03:20.370 --> 03:20.790 All right. 03:20.820 --> 03:22.380 Cell is initialized. 03:22.800 --> 03:24.600 We have everything in the void setup. 03:24.600 --> 03:29.880 Now in the void loop I'm going to do if cell dot. 03:30.990 --> 03:35.130 With a label like this with parentheses is greater. 03:35.130 --> 03:40.540 Strictly greater than zero means that we have received some data over Serial. 03:40.560 --> 03:43.650 Then we can read this and we are going to do string. 03:44.100 --> 03:48.510 Let's create a cmd variable which means command. 03:48.510 --> 03:52.620 So usually I prefer to write the full name for the variables. 03:52.620 --> 03:58.320 But when you have something like command where CMD is pretty clear and because we are going to use the 03:58.320 --> 04:03.030 CMD variable a lot in the following, so I'm just going to go with string cmd. 04:03.240 --> 04:03.780 Okay. 04:04.110 --> 04:05.670 Serial dot. 04:07.140 --> 04:11.530 Read string until end. 04:11.550 --> 04:15.690 Backslash n with important single quotes here. 04:16.500 --> 04:16.920 All right. 04:16.920 --> 04:17.850 And semicolon. 04:18.570 --> 04:24.440 So basically we use the same function as before, and now we have the comment. 04:24.450 --> 04:26.580 So we receive a comment from here. 04:26.730 --> 04:29.550 What we are going to do is we are going to check that comment. 04:29.550 --> 04:38.910 So if the comment is equal to UN, okay, So if you want to do a comparison with String with the Arduino 04:38.910 --> 04:41.850 string, you can simply use the two equal sign. 04:42.270 --> 04:47.340 So if the comment is on what do we do? 04:47.520 --> 04:51.690 Well, we do digital, right? 04:54.190 --> 05:01.150 With the pin and height and if the command is off. 05:01.150 --> 05:03.490 So let's do an else if actually. 05:04.060 --> 05:07.840 Command is off. 05:09.010 --> 05:14.950 We are going to do digital right led pin with low. 05:15.130 --> 05:16.390 So if we receive. 05:16.430 --> 05:17.950 On we power on the Led. 05:18.160 --> 05:26.890 If we receive off we power off the Led and then I'm going to add an else because well you could receive 05:26.890 --> 05:32.140 any string here you could receive on, you could receive off but you could receive anything. 05:32.140 --> 05:32.650 Okay. 05:32.650 --> 05:34.720 You don't know what's going to happen. 05:34.720 --> 05:37.540 You don't know what the other side is going to send. 05:37.570 --> 05:38.080 Okay. 05:38.080 --> 05:44.230 And as a basic principle, when you write some code like this, you don't trust the other side. 05:44.260 --> 05:44.650 Okay? 05:44.650 --> 05:47.110 Here you are writing the other side, so that's good. 05:47.110 --> 05:50.860 But usually don't trust what the other side sends you. 05:50.860 --> 05:51.370 Okay? 05:51.640 --> 05:57.680 So make sure to always check your receive on your receive off or you receive something else that can 05:57.680 --> 05:58.100 happen. 05:58.100 --> 05:58.580 Okay. 05:58.580 --> 06:05.360 So if you receive something else, well, what we're going to do in that case is just, well, nothing. 06:05.510 --> 06:07.160 So I'm going to keep it like that for now. 06:07.160 --> 06:12.890 But for example, you could print an error so you can send back an error, for example, or you can 06:12.890 --> 06:15.800 print an error on an LCD screen. 06:15.800 --> 06:18.230 Or you could do another behavior. 06:18.230 --> 06:21.050 For example, you could flush the input buffer. 06:21.050 --> 06:22.970 We are going to do that a bit later. 06:23.000 --> 06:23.510 Okay. 06:23.510 --> 06:26.780 But for now, you can see we check if we have some data. 06:26.780 --> 06:31.010 If yes, we read the data, that's going to be our command string. 06:31.040 --> 06:34.790 We check if it's equal to on, then we do an action. 06:34.790 --> 06:41.180 We check if it's equal to off, we do an action and then else everything else we can do something else 06:41.180 --> 06:43.310 that we want, but for now we do nothing. 06:43.310 --> 06:45.740 All right, let's now try this code. 06:45.770 --> 06:47.540 But we don't need to write the python code. 06:47.540 --> 06:49.640 We can just start this. 06:50.180 --> 06:53.780 Let's make sure that we have the Arduino plugged. 06:55.080 --> 06:55.890 Okay, let's. 06:55.890 --> 06:58.650 Oops, I have selected the wrong board. 06:58.650 --> 07:03.390 So tool Arduino Uno and the port is correct. 07:04.020 --> 07:11.610 Now I'm going to upload this, so let's save it as activity one. 07:12.270 --> 07:12.570 Okay. 07:12.570 --> 07:18.780 Enter compiling, uploading. 07:19.710 --> 07:25.740 And now that the code on the Arduino is running, what we can do is we can already try this behavior 07:25.740 --> 07:27.000 with the serial monitor. 07:27.000 --> 07:28.470 So we're going to open. 07:28.890 --> 07:34.380 So instead of having a python program running on the Raspberry Pi, we just have the serial monitor 07:34.380 --> 07:37.110 running on the Raspberry Pi and we can send command from there. 07:37.140 --> 07:37.620 All right. 07:37.620 --> 07:40.590 So make sure that you have the same baud rate here, okay? 07:41.640 --> 07:41.970 Check. 07:41.970 --> 07:42.780 This is correct. 07:42.780 --> 07:43.470 All right. 07:43.470 --> 07:48.510 And then new line, because we are going to send a new line character at the end. 07:48.540 --> 07:48.700 Okay. 07:48.720 --> 07:50.520 So we don't need to write it manually. 07:50.520 --> 07:52.320 And then I'm going to send some comments. 07:52.320 --> 08:03.090 So let's say I send on you can see the Led here is powered on now I send off the Led is powered off, 08:03.090 --> 08:06.450 I send on again and I can power on the Led. 08:06.480 --> 08:12.540 Now if I send let's say led on which is not correct nothing is going to happen led off. 08:12.750 --> 08:14.190 Nothing is going to happen. 08:14.190 --> 08:16.620 Any other string, nothing is going to happen. 08:16.620 --> 08:23.490 You can see we still have the X which is blinking because we are receiving some data, but then the 08:23.490 --> 08:30.360 data is processed in the code and it goes directly to the else which does nothing. 08:30.360 --> 08:30.740 Okay. 08:30.750 --> 08:34.530 So you have to send exactly the on and off command to do something. 08:34.530 --> 08:40.410 And you can see that with our experimentation, the behavior is correct here. 08:40.410 --> 08:44.560 So we can know that the Arduino code is correct. 08:44.560 --> 08:47.380 And now we can write the code on the Raspberry Pi. 08:47.920 --> 08:51.520 So let's start by initializing the communication. 08:51.520 --> 08:53.050 So I'm going to go with. 08:53.080 --> 08:59.500 So this is a bit of Python three for the interpreter. 08:59.500 --> 09:02.020 And then let's import Serial. 09:02.020 --> 09:05.170 Let's also import time because we're going to need that library. 09:06.450 --> 09:13.850 And I am going to do, sir, is equal to cereal dot cereal with the port. 09:13.860 --> 09:15.870 So the port is still the same for me. 09:16.410 --> 09:21.330 Slash dev slash tty ACM zero. 09:21.600 --> 09:21.840 Okay. 09:21.840 --> 09:23.580 The baud rate very important. 09:23.730 --> 09:25.740 Exact same here. 09:26.370 --> 09:28.470 And then the read timeout. 09:28.950 --> 09:31.830 Let's put one second. 09:32.490 --> 09:36.660 Well for this case, we don't really need the timeout here. 09:36.660 --> 09:41.280 The read timeout because we're not going to read anything but I still put it anyway. 09:41.460 --> 09:47.700 So here we open the cell communication and we get the cell in the cell object here. 09:48.210 --> 09:51.240 I'm not going to do the retry code, okay? 09:51.240 --> 09:55.590 Just to keep it simple for this activity, but you can do it if you want to. 09:55.620 --> 10:01.890 So once we have this, I'm going to do a time dot sleep with three seconds. 10:01.920 --> 10:02.330 Okay. 10:02.340 --> 10:08.550 To wait because this is going to connect to the Arduino and here on the Arduino, no, it's going to 10:08.550 --> 10:09.780 restart the program. 10:09.780 --> 10:13.620 So we make sure that we have spent enough time so the Arduino is ready. 10:13.770 --> 10:26.130 And then we're going to do set dot reset input buffer, which is well, not needed as well here because 10:26.130 --> 10:30.270 we don't have anything in the input buffer because the Arduino doesn't send anything. 10:30.270 --> 10:36.210 But still, I'm going to keep it for best practice because we're going to initialize the cell the same 10:36.210 --> 10:37.140 way every time. 10:37.140 --> 10:37.740 All right. 10:37.740 --> 10:40.830 And let's say print cell. 10:40.830 --> 10:41.310 Okay. 10:42.570 --> 10:43.470 Like this. 10:43.500 --> 10:46.980 Now what we can do is we can do our while. 10:47.970 --> 10:48.810 True. 10:48.810 --> 10:49.350 Okay. 10:49.740 --> 10:53.340 So this is kind of the void setup of the Raspberry Pi. 10:53.340 --> 10:54.860 And this is the void loop. 10:54.870 --> 10:59.190 All right, void setup, void loop, void setup and void loop. 10:59.190 --> 11:05.340 So while true, so what I'm going to do is, of course, I'm going to do a try and accept. 11:05.340 --> 11:18.190 So let's just put pass here, try accept keyboard interrupt and when we press Ctrl C, I'm going to 11:18.190 --> 11:18.730 do so. 11:18.730 --> 11:29.770 I'm going to say print close serial communication and set dot close before we exit the program. 11:29.770 --> 11:30.340 Okay. 11:30.880 --> 11:36.070 So again, this is going to be the same every time and in the while true. 11:36.100 --> 11:36.610 What do we do? 11:36.610 --> 11:38.890 So this is the behavior of our void loop. 11:38.890 --> 11:44.230 Well, basically, we want the user input and from that user input we send data to the Arduino. 11:44.320 --> 11:50.650 So I'm going to do, let's say user input is equal to input. 11:50.920 --> 11:51.460 Okay. 11:51.550 --> 11:55.390 I can put some text here to send some instruction. 11:55.390 --> 12:03.640 So for example, select on or off, All right. 12:03.670 --> 12:06.610 With a colon and a space. 12:06.610 --> 12:08.980 So we have this instruction. 12:09.010 --> 12:15.310 The input is going to block the program until we give something when we press enter and we're going 12:15.310 --> 12:17.860 to get that inside the user input variable. 12:17.890 --> 12:24.160 Once we have this, we could directly send the string to the Arduino because we validate the data here 12:24.160 --> 12:24.700 also. 12:24.700 --> 12:34.030 But we can also say, for example, if user input and how to validate this, well we want it to be on 12:34.030 --> 12:34.810 or off. 12:34.810 --> 12:37.150 So what we can do is in. 12:38.700 --> 12:41.350 On off. 12:41.970 --> 12:51.750 So basically, if the user input is in that list, which contains two values, then we're gonna do something. 12:51.750 --> 12:53.910 If not, so else. 12:53.940 --> 12:55.500 Basically, we don't do anything. 12:55.500 --> 12:57.270 So here I'm not going to put an else. 12:57.660 --> 13:05.340 So if the user input is correct, then we do set dot right and well, actually, I'm not just going 13:05.340 --> 13:13.320 to send user input, I'm going to add a backslash N Okay, so let's do for example str to send. 13:13.320 --> 13:20.610 So basically the string to send is equal to user input plus backslash. 13:20.610 --> 13:21.840 N okay. 13:21.840 --> 13:23.880 And we send str. 13:25.380 --> 13:25.890 Who censor. 13:25.890 --> 13:32.970 We write as STR to send dot encode with UTF eight. 13:33.780 --> 13:34.030 Okay. 13:34.050 --> 13:38.970 Make sure to do the encode on the string and not on the write function. 13:38.970 --> 13:42.000 Very important, so you should have open parentheses here. 13:42.030 --> 13:48.600 Open parentheses here and close and close at the end and well, it seems that pretty much it. 13:48.630 --> 13:55.020 Maybe we could add a print here so we can see on the Raspberry Pi side what's happening. 13:55.020 --> 13:57.360 So let's see. 13:57.600 --> 13:58.800 Let's print here. 13:59.220 --> 14:10.950 Print, send comments to Arduino with so plus user input. 14:12.790 --> 14:19.550 So we know that we are sending a command to the Arduino and then we can check if that works on the Arduino. 14:19.570 --> 14:25.030 If we correctly blink the Led, but we already know it works, so let's run that. 14:25.720 --> 14:29.920 I'm going to click on Run here and let's save this as. 14:31.330 --> 14:36.320 Activity one dot python. 14:36.340 --> 14:38.050 Okay, so we have the activity. 14:38.050 --> 14:42.530 One sketch for Arduino and the activity one python file. 14:42.550 --> 14:47.980 Let's press enter and let's see what we got here. 14:48.370 --> 14:49.320 Okay, so. 14:49.540 --> 14:51.900 Okay, select on or off. 14:51.910 --> 14:53.080 You can see the problem is stuck. 14:53.080 --> 15:02.320 Now the Arduino has reboot and now I'm going to send on and you can see we have the Led here which is 15:02.320 --> 15:03.130 powered on. 15:03.160 --> 15:06.340 I send off the Led is powered off. 15:06.340 --> 15:10.920 Let's send anything else, let's say led on nothing happens. 15:10.930 --> 15:13.240 Let's send on again it works. 15:13.570 --> 15:18.760 And now if I press Ctrl C, you can see close serial communication. 15:19.120 --> 15:22.000 All right, so that's the end of the first activity of this course. 15:22.000 --> 15:28.120 Now, if you have a slightly different code than me on both sides and if it still works well, that's 15:28.120 --> 15:28.630 great too. 15:28.630 --> 15:33.170 Okay, this so my solution is just one possible solution. 15:33.170 --> 15:33.560 All right? 15:33.560 --> 15:35.840 It is not the solution. 15:35.990 --> 15:41.930 And if you couldn't find the solution by yourself, well, don't worry, because as I told you, the 15:41.930 --> 15:44.690 activities here in this course are quite challenging. 15:44.690 --> 15:51.590 And what I recommend you to do is to actually come back to this activity maybe in 1 or 2 days or one 15:51.590 --> 15:52.100 week. 15:52.100 --> 15:58.880 Just watch the introduction of the activity again and then do it by yourself and you will see that it's 15:58.880 --> 16:02.870 going to be much easier for you and you're going to get more understanding. 16:02.990 --> 16:03.380 All right. 16:03.380 --> 16:05.420 And now let's go to the next activity.