WEBVTT 00:00.080 --> 00:04.710 Now that everything is correctly configured, let's start the communication. 00:04.730 --> 00:11.090 In this lesson, we will just initiate the communication and in the following lessons we will exchange 00:11.090 --> 00:13.460 some data between the two boards. 00:13.460 --> 00:19.010 So we are going to open the Arduino IDE. 00:21.370 --> 00:24.430 So we can upload some code to the Arduino board. 00:26.170 --> 00:35.680 And we are also going to open the thorny python so we can write some Python code on the Raspberry Pi. 00:35.920 --> 00:39.610 So I'm going to organize like this. 00:41.860 --> 00:46.750 Okay, so I can have the Arduino code on one side and the python code on the other side. 00:46.780 --> 00:47.170 Okay. 00:47.170 --> 00:49.060 So this is going to run on the Arduino. 00:49.090 --> 00:51.420 This is going to run on the Raspberry Pi. 00:51.430 --> 00:56.680 And as you can see, that's very practical that we have the Arduino IDE on the Raspberry Pi so we can 00:56.680 --> 00:59.530 directly write the two programs on the same place. 00:59.530 --> 01:03.370 And we are going to start with the Arduino side. 01:03.400 --> 01:03.700 Okay. 01:03.700 --> 01:05.440 Usually that's what we're going to do. 01:05.470 --> 01:09.220 We're going to start from Arduino because that's going to be easier to debug. 01:09.220 --> 01:18.130 So to start serial communication, well, you just do serial dot begin with a baud rate. 01:18.130 --> 01:22.750 So that is quite classic baud rate 9600. 01:23.170 --> 01:23.500 Okay. 01:23.500 --> 01:27.910 And you put this line inside the void setup of your Arduino, Okay. 01:27.910 --> 01:33.280 You have void setup which is going to be executed once and void loop, which is going to be executed 01:33.280 --> 01:35.340 an infinite number of times. 01:35.350 --> 01:38.890 So with this, we have initialized Serial on the Arduino. 01:38.890 --> 01:40.180 So that's very simple. 01:40.180 --> 01:48.080 What we can do also, and this is going to depend on the Arduino board that you have is do while and 01:48.080 --> 01:57.470 then exclamation mark for not serial and then just open close curly brackets. 01:57.470 --> 02:03.890 So this basically on the Arduino Uno, for example, or Nano or mega, you don't need this line. 02:03.890 --> 02:11.390 But if you are using an Arduino with a native USB, for example, Arduino, Leonardo or Arduino zero, 02:11.420 --> 02:13.250 then you may need to use this line. 02:13.250 --> 02:15.890 Otherwise the style is not going to work correctly. 02:15.890 --> 02:21.200 So basically this is going to wait until the serial is ready. 02:21.200 --> 02:27.800 So I'm just going to include it here and in every program I do so that this code is going to work on 02:27.800 --> 02:29.510 pretty much any Arduino board. 02:29.510 --> 02:33.590 But if you are using Arduino Uno like me, you don't need this. 02:33.980 --> 02:34.370 All right. 02:34.370 --> 02:36.260 So that's the code for the Arduino part. 02:36.290 --> 02:41.870 Now I'm going to go on the Raspberry Pi part and write some Python program. 02:41.990 --> 02:49.220 So let's first start with this user bin env with Python three. 02:49.250 --> 02:49.490 Okay. 02:49.490 --> 02:55.640 So if we ever execute this from the terminal directly, we give the information that the interpreter 02:55.640 --> 02:56.990 is Python three. 02:57.020 --> 03:02.570 Now what we're going to do is we're going to first import serial. 03:02.600 --> 03:08.330 Okay, so the name of the library is Pi serial, but you're going to import Serial. 03:08.360 --> 03:08.930 Okay. 03:09.050 --> 03:11.310 On the Arduino, you have nothing to import. 03:11.330 --> 03:11.570 Okay. 03:11.570 --> 03:16.460 Soil is already there, but on the Raspberry Pi, you have to import that module. 03:16.460 --> 03:16.940 And then. 03:16.940 --> 03:21.380 Well, the first thing we're going to do is to open the serial communication. 03:21.380 --> 03:27.320 And the serial communication is going to give us something that I'm going to save as sell for sale. 03:27.350 --> 03:27.620 Okay. 03:27.620 --> 03:29.390 I do this because that's quite common. 03:29.390 --> 03:34.550 And if you find any help on the Internet, any tutorial, any documentation, that's what you're going 03:34.550 --> 03:34.820 to see. 03:34.820 --> 03:39.140 So I'm going to keep the convention that is on the Internet. 03:39.160 --> 03:39.620 Right? 03:39.620 --> 03:42.920 And so sale is equal to serial dot. 03:43.650 --> 03:49.280 Serial uppercase with the uppercase U open close parentheses. 03:49.290 --> 03:52.650 And first we are going to give the port. 03:53.100 --> 04:00.900 Okay, So if you remember the port was slash dev slash tty ACM zero. 04:00.900 --> 04:04.800 So that is the port I have found actually in the previous lesson. 04:04.890 --> 04:04.970 Okay. 04:05.010 --> 04:10.560 So if you are not sure what port is yours because that may be something different here, please go back 04:10.560 --> 04:17.250 to the previous lesson on how to set up serial communication and then come back here with the port that 04:17.250 --> 04:18.720 corresponds to your Arduino. 04:18.750 --> 04:21.360 The next parameter is the baud rate. 04:21.360 --> 04:24.660 So the baud rate is actually what you can see here. 04:24.660 --> 04:27.270 That's the speed of communication basically. 04:27.270 --> 04:30.090 And this is super, super important. 04:30.090 --> 04:34.800 You have to have the same baud rate on both sides of the communication. 04:34.800 --> 04:34.950 Okay. 04:34.950 --> 04:40.230 If you have a different baud rate, then the two programs can't understand each other. 04:40.230 --> 04:46.120 And actually speaking of baud rate, this is the pretty common classic baud rate you're going to have 04:46.120 --> 04:49.900 in every tutorial, but it's also a pretty slow one. 04:49.930 --> 04:55.030 You can go up to 115,002 hundred baud. 04:55.150 --> 04:55.540 Okay. 04:55.540 --> 04:57.430 And that's the baud rate I'm going to use. 04:57.430 --> 05:01.810 So if I use this here, I use this here also. 05:02.050 --> 05:02.440 Okay. 05:02.440 --> 05:04.390 So you can have different values, okay? 05:04.390 --> 05:06.550 You have different common values. 05:06.550 --> 05:11.620 And this is one of the most common one and also a quite fast one. 05:11.620 --> 05:14.800 And it's better than the classic 9600. 05:14.890 --> 05:21.070 And I'm going to add a third parameter, which is timeout, let's say 1.0. 05:21.070 --> 05:24.370 So timeout here is read timeout. 05:24.370 --> 05:26.980 I'm going to come back to that a bit later in the course. 05:26.980 --> 05:28.840 Okay, So don't worry about that for now. 05:28.900 --> 05:29.410 All right. 05:29.410 --> 05:36.970 So with this line, we open the serial communication and if it works, okay, we're going to get the 05:36.970 --> 05:38.950 serial inside this cell. 05:39.130 --> 05:43.600 If it doesn't work, we're going to get an error and the program is going to exit. 05:43.630 --> 05:50.140 Then what I recommend you to do is to wait a few seconds here after opening the communication. 05:50.140 --> 05:57.400 So I'm going to do import time and do time dot sleep for three seconds. 05:57.400 --> 06:00.130 So I recommend at least two seconds. 06:00.130 --> 06:06.550 Three is even better because, well, when you open the serial communication on that side, the thing 06:06.550 --> 06:12.970 is that on the Arduino side, the Arduino for Arduino Uno, for example, is going to restart. 06:12.970 --> 06:15.040 So the program is going to be restarted. 06:15.040 --> 06:21.460 So what you want to do on the Raspberry Pi side is to give enough time for the Arduino to have the serial 06:21.460 --> 06:23.800 completely ready to communicate. 06:23.800 --> 06:29.080 And so we give three seconds here, and I recommend you do that because if you don't do that and you 06:29.080 --> 06:35.740 try to read some data or just send some data just after that, you're going to experience some weird 06:35.770 --> 06:37.030 bugs in your program. 06:37.030 --> 06:39.160 And that's going to be hard actually to debug. 06:39.160 --> 06:43.300 So better have a time.sleep with 2 or 3. 06:43.300 --> 06:51.040 And then I'm going to do set dot reset input buffer. 06:51.850 --> 06:53.230 So what is this? 06:53.230 --> 06:57.760 So basically with serial, both sides can communicate with the other. 06:57.790 --> 06:58.000 Okay. 06:58.000 --> 07:04.090 So I can send data from the Raspberry Pi to the Arduino and I can send data from the Arduino to the 07:04.090 --> 07:06.940 Raspberry Pi when the data arrives. 07:06.940 --> 07:08.530 It's not directly in the code. 07:08.530 --> 07:11.590 When the data arrives, it's in a buffer. 07:11.620 --> 07:11.860 Okay? 07:11.860 --> 07:16.150 And when you're going to read, that's what we're going to see in the next lesson. 07:16.150 --> 07:20.110 So when you're going to read, you're going to read actually from the buffer. 07:20.110 --> 07:27.790 So here we reset the input buffer, which means that if the Arduino sends us some data before this, 07:27.970 --> 07:32.410 so when the program is actually paused, we're going to erase everything. 07:32.410 --> 07:37.630 So we start after this line with a fresh buffer that has nothing in it. 07:37.630 --> 07:38.050 Okay. 07:38.050 --> 07:42.130 And I'm going to come back also later in the course to explain more about it. 07:42.130 --> 07:42.490 All right. 07:42.490 --> 07:42.940 So that's it. 07:42.970 --> 07:45.130 Now let's maybe put print. 07:46.420 --> 07:47.110 Sale. 07:47.320 --> 07:47.950 Okay. 07:49.290 --> 07:51.240 To have a nice confirmation and then. 07:51.240 --> 07:53.130 Well, the problem is going to exit. 07:53.520 --> 07:54.870 Okay, Now what to do? 07:54.870 --> 07:59.280 Because we have the Arduino program here, the Raspberry Pi program here. 07:59.280 --> 08:04.730 But what you need to do first is to upload the Arduino code on the Arduino IDE. 08:04.890 --> 08:05.340 Okay. 08:05.370 --> 08:06.840 That's the first thing to do. 08:06.840 --> 08:09.390 Always is to have the Arduino ready. 08:09.390 --> 08:11.280 So I'm going to go on tools. 08:12.220 --> 08:18.670 Check that I have the correct board, the correct spot and let's do upload. 08:19.660 --> 08:19.930 Okay. 08:19.930 --> 08:25.030 Let's save it as first communication. 08:27.110 --> 08:27.350 Okay. 08:27.350 --> 08:28.190 You can see. 08:28.280 --> 08:31.610 Compiling and uploading and down uploading. 08:31.610 --> 08:34.460 So the code is now in the Arduino. 08:34.490 --> 08:39.980 Now that the code is in the Arduino, we go back here and I'm going to save the file. 08:39.980 --> 08:41.960 So save as. 08:43.100 --> 08:44.720 So let's create a new folder. 08:44.720 --> 08:46.210 Actually, let's go here. 08:46.220 --> 08:48.650 So I'm going to do directly from the file manager. 08:48.890 --> 08:49.430 Okay. 08:49.730 --> 08:56.360 Right click new folder, Let's call it Python programs. 08:56.690 --> 08:57.830 Okay? 08:58.010 --> 09:00.080 And let's go back here. 09:00.080 --> 09:02.930 Let's do save as. 09:03.950 --> 09:05.390 In Python program. 09:06.640 --> 09:11.230 First communication and dot pi. 09:11.260 --> 09:13.240 So that's the python file. 09:13.630 --> 09:14.110 Click on. 09:14.110 --> 09:14.840 Okay. 09:14.860 --> 09:17.950 So the program is saved and now I can run it. 09:17.980 --> 09:23.290 So to run it, I can just click on the play button here or run from the terminal. 09:23.290 --> 09:25.390 So I'm just going to click here. 09:27.080 --> 09:33.540 And you can see we have so we run the script and after three seconds we have cereal. 09:33.590 --> 09:34.330 Okay? 09:34.340 --> 09:39.350 Which means that the Raspberry Pi could correctly connect to that port. 09:39.380 --> 09:39.810 Okay. 09:39.830 --> 09:42.830 So it could correctly connect to the Arduino. 09:42.860 --> 09:51.470 Now, one important thing you have to do also on the Python side is that so here we directly exit after 09:51.470 --> 09:51.800 this. 09:51.800 --> 09:54.590 So we open communication and then we exit. 09:54.620 --> 10:01.790 What you have to do and what is better is to close the communication so you can do self dot close. 10:02.540 --> 10:02.830 Okay. 10:02.840 --> 10:07.490 Before you exit the program or whenever you want to close the communication. 10:07.490 --> 10:11.750 So with this, you're going to open the communication with this, you're going to close it. 10:11.750 --> 10:16.070 And on the Arduino side, you don't need to actually close the communication. 10:16.070 --> 10:16.250 Okay? 10:16.250 --> 10:20.870 The communication is going to be closed simply when you power off the Arduino. 10:20.870 --> 10:27.780 But here as a best practice, it's better to close it because then if it's not closed correctly and 10:27.780 --> 10:31.530 you try to run another program, you may have some troubles. 10:31.740 --> 10:33.480 Okay, So let's run that again. 10:33.990 --> 10:39.960 You can see we wait three seconds, say okay, and then we close the communication here. 10:39.990 --> 10:41.060 Everything is good. 10:41.070 --> 10:47.550 Now, let's say that, for example, I don't have my Arduino board connected to the Raspberry Pi, so 10:47.550 --> 10:53.880 I have physically removed the USB cable from the Arduino side or the Raspberry Pi side. 10:53.880 --> 10:54.990 It doesn't really matter. 10:54.990 --> 10:57.420 And I'm going to run the script again. 10:58.340 --> 11:00.170 And you can see we have an error. 11:00.470 --> 11:00.920 Okay. 11:00.920 --> 11:03.050 We have an error, which is quite big. 11:03.050 --> 11:06.680 But at the end you can see single exception. 11:07.700 --> 11:12.580 Could not open port slash dev slash zero. 11:12.830 --> 11:13.270 Okay. 11:13.280 --> 11:15.650 So basically the port is not found. 11:15.680 --> 11:16.100 Why? 11:16.130 --> 11:18.290 Because the Arduino is not connected. 11:18.320 --> 11:21.950 If I plug the Arduino to the Raspberry Pi again. 11:22.160 --> 11:23.450 Let's run the code. 11:23.450 --> 11:25.400 And now it's working. 11:27.090 --> 11:27.720 Great. 11:29.380 --> 11:32.800 So to recap on the steps here, that's very important. 11:32.830 --> 11:39.040 First, you will need to write some code for the Arduino where you initialize Serial, of course, and 11:39.040 --> 11:41.350 you need to upload that to the Arduino. 11:41.380 --> 11:47.320 When you upload to the Arduino, make sure that you are not currently talking to the Arduino from another 11:47.320 --> 11:48.640 program of your Raspberry Pi. 11:48.680 --> 11:49.080 Okay. 11:49.090 --> 11:54.290 Because when you upload and when you communicate, you use the same cellular communication. 11:54.310 --> 11:54.870 Okay. 11:54.880 --> 12:00.250 So if you are sending data from your Raspberry Pi to the Arduino with a Python program and you try to 12:00.250 --> 12:02.590 upload, you may have some problems. 12:02.890 --> 12:03.220 Okay. 12:03.220 --> 12:08.830 Now that the code is on the Arduino, the code is going to run as soon as the Arduino is powered on. 12:08.830 --> 12:13.930 And then you can run your Python script where you open the serial communication. 12:13.930 --> 12:16.840 So make sure you have the same baud rate. 12:16.960 --> 12:17.190 Okay? 12:17.200 --> 12:19.150 And make sure you have the correct port here. 12:19.150 --> 12:25.380 And basically on some boards like Arduino, Uno, Nano Mega, for example, when you open the serial 12:25.390 --> 12:30.800 communication from the outside of the Arduino, the Arduino program is going to be reset. 12:30.890 --> 12:32.350 It's going to be restarted. 12:32.360 --> 12:38.300 So at this point of the code, this is going to be restarted from scratch. 12:38.300 --> 12:41.060 So that's why you want to wait a few seconds. 12:41.060 --> 12:42.830 So here we wait three seconds. 12:42.830 --> 12:49.640 That's very safe so that the cell communication can correctly be initialized and everything can be initialized 12:49.640 --> 12:50.990 on the Arduino side. 12:51.020 --> 12:53.050 Then you reset the input buffer. 12:53.060 --> 12:56.960 You do whatever you want to do here, you can send and receive data. 12:56.960 --> 13:00.200 That's what we're going to see directly in the following lesson. 13:00.200 --> 13:07.550 And then you close the communication here on the Raspberry Pi side and you can exit the program.