WEBVTT 00:00.560 --> 00:07.070 In this laboratory lesson, we're going to develop a code for the Arduino that constantly reads the 00:07.070 --> 00:11.150 serial port, listening for new messages coming from Ros2. 00:11.810 --> 00:18.650 Additionally, upon receiving a new message, it will turn on or off the Led that is integrated on the 00:18.650 --> 00:19.280 board. 00:19.860 --> 00:26.460 To complete this lesson, you will need the Arduino board and a USB cable to connect it to your PC. 00:27.690 --> 00:30.480 All the code we are going to write during this lesson. 00:30.480 --> 00:36.900 Use a programming language that is a variant of the Cplusplus specifically designed for the Arduino. 00:37.320 --> 00:42.690 If you are familiar with Cplusplus, then you will have no difficulties into following along with the 00:42.690 --> 00:46.140 development, even if you never used the Arduino before. 00:46.620 --> 00:52.020 However, if you are not familiar with Cplusplus, it might be a bit more challenging to understand 00:52.020 --> 00:52.800 the code. 00:52.830 --> 00:58.290 Nevertheless, as I always say, this is not a programming course but a robotics course. 00:58.290 --> 01:05.520 So try to grasp the key concepts and the logic rather than the syntax of the language that we are using. 01:05.820 --> 01:13.320 In the following lessons, we are going to develop both Python and Cplusplus node for Ros2 to send messages 01:13.320 --> 01:15.000 to the Arduino serial port. 01:15.000 --> 01:20.520 And with this we are going to enable the communication between the Ros two and the Arduino. 01:20.800 --> 01:26.040 Then also in the following lessons, we are also going to enable the reverse communication. 01:26.040 --> 01:31.210 So the one from Arduino to Ros two enabling Arduino to send messages to Ros two. 01:31.930 --> 01:38.110 Let's start by creating a new rescue package that will contain all the code developed in this section. 01:38.350 --> 01:42.700 So let's go to our workspace and to the source folder. 01:42.700 --> 01:45.270 And here let's create a new package. 01:45.280 --> 01:50.230 So you are already familiar with the rescue package, create command. 01:50.230 --> 01:55.880 And in this case, let's use as build type and. 01:57.570 --> 02:03.630 See make as we are going to insert both Python and C plus plus scripts in this package. 02:03.720 --> 02:10.380 And then let's name this package, Arduino Bot firmware. 02:10.530 --> 02:12.210 So let's press enter. 02:12.210 --> 02:16.500 And this has created our new Arduino Bot firmware package. 02:16.500 --> 02:23.820 Then let's go back to the workspace and let's build it so that the new package is recognized and is 02:23.820 --> 02:25.080 available in Ros two. 02:25.110 --> 02:31.050 So this one since in this lesson we want to develop the code for the Arduino board, which receives 02:31.080 --> 02:35.310 a command from the serial port and turns on or off a Led. 02:35.340 --> 02:42.000 Accordingly, we are going to use the Arduino IDE, which had you download in one of the early setup 02:42.000 --> 02:42.630 lessons. 02:42.630 --> 02:43.950 So this one. 02:44.560 --> 02:47.410 In this ID, so let's make it bigger. 02:47.500 --> 02:53.770 Besides writing and compiling the code for the board, we can also directly upload the code to the board 02:53.770 --> 02:56.500 once we are going to connect it through the USB cable. 02:56.500 --> 03:01.390 So here we can compile it and here we can also upload the code to the board. 03:02.060 --> 03:08.810 By default, when we create a new project within the Arduino IDE, it comes initialized with a script 03:08.810 --> 03:14.180 that contains two functions the setup function and the loop function. 03:14.420 --> 03:15.500 The first one. 03:15.500 --> 03:21.890 So this one, the setup function will contain all the instructions that the Arduino needs to execute 03:21.890 --> 03:25.490 only once, so only at the startup of the board. 03:25.750 --> 03:28.070 Instead, the loop function. 03:28.070 --> 03:34.820 This one will contain all the instructions that the Arduino needs to execute repeatedly so at regular 03:34.820 --> 03:38.300 time intervals defined by the controller's frequency. 03:38.630 --> 03:41.410 So let's start by defining a new global variable. 03:41.420 --> 03:46.010 So let's go here and let's define a new global variable. 03:47.120 --> 03:53.540 And let's call this one let pin and let's set it to 13. 03:53.720 --> 04:00.020 This indicates the number of the pin that is on the Arduino board to which the Led is connected. 04:00.020 --> 04:04.890 And this is the onboard Led that is already integrated with the board itself. 04:05.190 --> 04:11.610 And we want to turn this led on or off based on the message that was received on the serial port. 04:12.000 --> 04:18.300 So now in the setup function, so the one that is executed only once when the controller starts up, 04:18.390 --> 04:20.790 we need to initialize this specific pin. 04:20.790 --> 04:24.570 So the PIN 13 where the Led is connected. 04:24.660 --> 04:37.080 And so let's use the function pin mode to set the Led pin variable and to set this one of type output. 04:37.170 --> 04:44.190 So basically with this instruction we are setting that we want to send an output command to this pin 04:44.190 --> 04:47.550 here in order to turn on or off the Led. 04:48.700 --> 04:49.540 By default. 04:49.540 --> 04:55.360 So at the controller start up, still in the setup function, we want the Led to be off. 04:55.570 --> 05:08.320 So let's use the digital write function to write on the Led pin and let's write a low tension. 05:08.320 --> 05:12.580 And so this basically will turn off the Led if it was on. 05:13.330 --> 05:15.910 Next, still in the setup function. 05:15.910 --> 05:18.790 Let's also initialize the serial communication. 05:18.790 --> 05:28.660 So the serial communication with the our PC and so with the Ros two world and let's use the serial begin. 05:28.900 --> 05:32.500 And within this function we have to specify the bound of the connection. 05:32.500 --> 05:41.440 So let's set it to 115 200 and additionally let's set the timeout for the serial communication. 05:41.440 --> 05:47.920 So serial set timeout and let's set a timeout of one. 05:48.710 --> 05:54.710 With this, the board initialization is completed, so the setup function is completed and now we can 05:54.710 --> 05:57.590 move on to define the behavior of the loop function. 05:57.590 --> 06:02.150 So the one that is executed repeatedly after the setup function. 06:02.420 --> 06:10.940 So here, let's check if we have any new messages on the serial port with the instruction serial available. 06:12.530 --> 06:17.120 So if there is any new message available on the serial port. 06:17.120 --> 06:20.960 So this means that our Ros two node sent a new message to the Arduino. 06:20.990 --> 06:24.350 Now we want to read this message within the Arduino. 06:24.530 --> 06:28.820 So to read this message, let's use the serial read. 06:32.030 --> 06:35.870 String function and let's convert this one to an integer. 06:36.110 --> 06:42.410 Since we know that all the messages that we are going to receive from our ros2 node are going to be 06:42.410 --> 06:43.190 integers. 06:43.400 --> 06:48.890 And let's store the output of this function into a new variable called X. 06:49.310 --> 06:52.850 And now let's check which is this message that we have just received. 06:52.880 --> 06:55.790 So basically, let's check which is the message. 06:55.790 --> 06:59.360 So the content of the message that we have just received. 06:59.570 --> 07:05.720 So if the value of X is equal to zero. 07:06.050 --> 07:09.170 Now, in this case, we want to turn off the Led. 07:09.290 --> 07:11.330 So let's use again the digital. 07:13.630 --> 07:18.910 Write function to write on the pin of delete. 07:18.910 --> 07:21.610 And we want to write again a low tension. 07:21.610 --> 07:30.640 So in order to turn off the light, otherwise so else if we receive any other number, so any other 07:30.640 --> 07:33.430 command we want to turn on delete. 07:33.430 --> 07:42.310 So again, let's use the digital write function to write on the Led pin. 07:42.310 --> 07:45.490 And in this case we want to write an high voltage. 07:45.490 --> 07:51.070 And so basically this will turn on the Led finally at the end of the if statement. 07:51.070 --> 07:59.770 So here in order to avoid this loop to be executed too rapidly, let's add a small delay of 0.1. 08:01.240 --> 08:07.330 With this, we have completed our very simple script for the Arduino that receives a message from the 08:07.330 --> 08:13.570 serial port and turns off or on the Led based on the message that we have received. 08:14.080 --> 08:16.450 Now let's save this file. 08:16.450 --> 08:25.210 So with Ctrl s and let's save it within our workspace and so within the new package that we have created. 08:25.210 --> 08:34.030 So the Arduino bot firmware and here let's create a new folder called firmware and this will contain 08:34.030 --> 08:38.370 all the code for the Arduino that we are going to develop in this section. 08:38.380 --> 08:39.910 And let's call this one. 08:39.910 --> 08:46.270 So let's call this script simple serial receiver. 08:46.480 --> 08:48.970 So let's save it under this name. 08:50.640 --> 08:57.510 Let's conclude this lesson by compiling and loading this code into the Arduino board so we can compile 08:57.510 --> 09:00.240 it to verify that there are no no errors. 09:00.240 --> 09:03.810 And actually we can see that there is an error indeed. 09:04.640 --> 09:06.380 Because here there is a typo. 09:06.500 --> 09:08.810 Time out. 09:09.290 --> 09:11.870 Let's save and let's compile again. 09:12.290 --> 09:16.940 And now we can see that it compiled properly so there are no more errors. 09:17.750 --> 09:19.910 And now let's save it one more time. 09:20.630 --> 09:26.660 And now we can connect our Arduino board to our PC using a USB cable. 09:34.920 --> 09:40.500 And before uploading the code to the board, we need to configure the Arduino ID to indicate the type 09:40.500 --> 09:44.970 of the Arduino board that we are using and also the port to which it is connected. 09:45.270 --> 09:51.440 So in the tools section, let's change the board to the board that you are using. 09:51.450 --> 09:56.610 In my case, I'm using an Arduino Uno and then still in the tools section. 09:56.640 --> 09:58.170 Let's set the port. 09:58.170 --> 10:04.350 And here, as you can see, the Arduino IDE was able to automatically detect that at the port. 10:04.380 --> 10:08.480 ACM zero in my case is connected an Arduino Uno. 10:08.550 --> 10:14.160 So let's click on this port and be aware that in your case it can be connected, for example, to a 10:14.160 --> 10:16.650 different port with a different name. 10:17.040 --> 10:22.170 So once you select the port correctly, now we can click on upload. 10:23.020 --> 10:28.810 And this command will first compile the code to check for any errors, and then we load it into the 10:28.810 --> 10:32.470 Arduino boards and also it will automatically start its execution.