WEBVTT 00:00.290 --> 00:07.940 In this laboratory lesson, we will use some tools from the TF2 Library of Ros two to create a C plus 00:07.940 --> 00:14.570 plus service server for the conversion of the orientation of an object from its representation in quaternion 00:14.570 --> 00:17.210 to Euler angles and vice versa. 00:17.810 --> 00:23.180 The service will be useful during the course whenever you want to know the corresponding Euler angles 00:23.180 --> 00:25.640 for a given quaternion or vice versa. 00:26.720 --> 00:33.050 If you haven't followed the previous Python laboratory lesson, then you need to create a new package 00:33.050 --> 00:34.790 in our workspace. 00:34.910 --> 00:42.200 So let's open a terminal and here let's go to the Arduino bot workspace and then to the source folder. 00:42.200 --> 00:47.780 And here where we have already created all the packages that implement the functionalities of the robot 00:47.780 --> 00:48.620 so far. 00:48.830 --> 00:50.920 We need to create a new package. 00:50.930 --> 00:57.590 So, so if you haven't already, we have to create the Arduino bot utils package and we can do so with 00:57.590 --> 01:01.520 the command ros2 package create. 01:01.520 --> 01:03.710 Then let's choose the build type. 01:04.910 --> 01:11.180 And in this case, as we are going to include both Python and C plus plus node in this package, let's 01:11.180 --> 01:21.050 use the Amend CMake as a build type and the package is called Arduino bot utils so you can press enter 01:21.050 --> 01:22.640 to create this package. 01:22.730 --> 01:26.820 I already have it so I will not create it. 01:26.820 --> 01:31.110 And then you need to go back to the workspace and run the command. 01:31.140 --> 01:34.170 Click on Build in order to rebuild the workspace. 01:34.170 --> 01:41.070 And so in order for the new package, so for the Arduino bot utils package to be recognized in Ros two 01:41.610 --> 01:44.430 now we can go back to Visual Studio code. 01:44.760 --> 01:50.850 So let's open Visual Studio code and let's open the Arduino bot utils package that we have just created. 01:51.210 --> 01:58.170 As usual, let's place all the C plus plus source code inside the SRC folder. 01:58.170 --> 02:06.630 So here let's create a new file called Angle Conversion dot CP. 02:07.470 --> 02:13.110 This file will contain the actual code for the conversion between the angular angles and quaternion 02:13.110 --> 02:14.310 and vice versa. 02:15.440 --> 02:21.590 In this script, we are going to create two service server inside our EC2 node, one for the conversion 02:21.590 --> 02:25.370 to Quaternion to Euler and the other one for the opposite conversion. 02:25.370 --> 02:27.410 So from Euler to quaternion. 02:27.770 --> 02:33.710 However, instead of rewriting the code that we already know, we can copy the content of the simple 02:33.710 --> 02:34.790 service server. 02:34.790 --> 02:40.430 So the one that we developed in the Arduino bot CP examples in the source folder. 02:40.430 --> 02:47.660 So let's open the simple service server and let's copy all the content and let's paste it here. 02:47.660 --> 02:50.960 So let's paste it in the angle conversion. 02:51.080 --> 02:54.650 And now let's start by changing the name of the class. 02:54.650 --> 02:59.960 So let's call this one angles converter. 02:59.960 --> 03:04.250 And still this one inherits from the CP node class. 03:04.340 --> 03:11.000 Let's change also the name of the constructor and also within the bind function, Let's change the name 03:11.000 --> 03:12.140 of the class. 03:12.500 --> 03:14.630 Now let's change the name of the node. 03:14.630 --> 03:20.670 So here, let's call the node angles Conversion. 03:22.530 --> 03:23.520 Service. 03:23.910 --> 03:27.710 And now let's start by creating two service servers. 03:27.720 --> 03:31.840 So here with this instruction, we create one service server. 03:31.860 --> 03:37.620 So let's copy this one and let's paste it below in order to create the second one. 03:38.290 --> 03:40.780 Let's call the first service server. 03:40.870 --> 03:43.090 User two Quaternion So. 03:47.520 --> 03:53.130 And so let's also change the name of this variable here among the private variables. 03:53.700 --> 03:56.130 So this is the Euler to quaternion. 03:56.490 --> 03:59.930 Let's also create a new private variable. 03:59.940 --> 04:06.150 So a new instance of the service class by a new shared pointer of the service class. 04:06.150 --> 04:14.690 And let's call this one, as you might have imagine, quaternion to user. 04:15.240 --> 04:23.420 And so let's store the content of the quaternion to user as the output of the create service function. 04:23.430 --> 04:25.890 So let's call the first service. 04:25.890 --> 04:31.920 So the one that we are storing in the user to quaternion variable, let's call it as well, user to 04:31.950 --> 04:32.760 quaternion. 04:33.000 --> 04:34.320 And the second one. 04:34.320 --> 04:40.320 So the second service, let's call it quaternion to Euler, and these are the two names. 04:40.320 --> 04:45.360 So Euler to quaternion and Quaternion to Euler are the two names of the service servers. 04:45.360 --> 04:52.030 So the one that in Ros2 will be available for the client to interact with these two services. 04:52.510 --> 04:56.260 Then let's also change the message that we are going to print in the terminal. 04:56.470 --> 05:05.410 And so let's says Angle conversion services are ready. 05:05.590 --> 05:12.130 So let's print this message here and now we need to change also the name of the callback function that 05:12.130 --> 05:14.560 each of these two service server calls. 05:14.770 --> 05:20.470 So for example, the first callback function, so the one executed by the user to quaternion service 05:20.500 --> 05:34.840 is also called Euler to Quaternion callback, and the second one is called Quaternion to Euler callback. 05:34.840 --> 05:41.320 So these are the two callback functions that are executed and still both of them receive two parameters 05:41.320 --> 05:44.770 as input that are the request and response message. 05:44.770 --> 05:49.120 So the interface message for the communication with the service server. 05:49.300 --> 05:52.240 So let's declare also these two functions. 05:52.240 --> 05:54.670 So the other two quaternion callback. 05:54.670 --> 06:03.850 So let's for example, rename the service callback into Euler to Quaternion, then let's leave its content 06:03.850 --> 06:04.570 empty. 06:04.990 --> 06:12.400 Let's copy this function and let's paste it below in order to declare the second callback function. 06:12.400 --> 06:20.010 So this one that is the quaternion to Euler callback before proceeding to define the logic of the two 06:20.020 --> 06:25.900 callback functions, we need to remember to define the communication interface with the two services. 06:25.900 --> 06:31.120 So as you can see now we are still using the old one that was the add to interface. 06:31.240 --> 06:37.030 This means that we need to define how the request and the response message of the new service server 06:37.030 --> 06:40.390 should look like for the interaction with the service. 06:40.780 --> 06:46.930 If you haven't followed me in the Python laboratory lessons, we need to define these interfaces inside 06:46.930 --> 06:49.210 the Arduino bot messages package. 06:49.210 --> 06:53.800 So inside this package here, inside the SRB folder. 06:53.800 --> 07:01.960 So we need to create two new more interfaces, two new more files, the Euler two quaternion XV and 07:01.960 --> 07:04.090 the Quaternion two Euler SRB. 07:04.540 --> 07:08.950 Let's start from the first one, the Euler two Quaternion interface. 07:09.220 --> 07:16.090 In this case, the request message contains three decimal number three floating points that are the 07:16.090 --> 07:18.790 three components, the three Euler angles. 07:18.790 --> 07:20.860 So roll pitch and yaw. 07:21.130 --> 07:27.640 And the response message instead contains four element, four decimal numbers that are the four components 07:27.640 --> 07:32.050 of the quaternion that here we called X, y, z, and W. 07:32.440 --> 07:37.720 The second interface that we need to declare is the quaternion to Euler interface. 07:37.720 --> 07:45.370 And within this file, the request message this time is composed of four variables of four decimal numbers 07:45.370 --> 07:49.420 that are X, Y, z and W, and the second one. 07:49.420 --> 07:56.320 So the response message is composed of three components that are the three rotation of the Euler angles. 07:56.320 --> 07:58.240 So the roll pitch and yaw. 08:00.130 --> 08:07.000 Then in order to ensure that both of these interfaces are recognized and compiled, let's also add these 08:07.000 --> 08:10.330 ones into the cmakelists.txt. 08:10.630 --> 08:18.250 And so here, where we have already defined the Add interface, we need to add two more lines that are 08:18.280 --> 08:25.060 the ones to declare the Euler to quaternion interface and the quaternion to user interface. 08:25.240 --> 08:27.490 And now we can save this file. 08:27.730 --> 08:31.540 And also before using these two interfaces within our script. 08:31.540 --> 08:37.480 So within our angle conversion file, let's open a new terminal and let's build the workspace. 08:37.900 --> 08:45.490 So let's go into the workspace and let's build it in order for the two new interfaces to be compiled 08:45.490 --> 08:48.100 and so that we can use them in our script. 08:48.670 --> 08:53.750 So once this is compiled, we can start importing the interface. 08:53.770 --> 09:01.560 So still here we can reuse this line and still from the Arduino bot messages libraries from the SRB 09:01.570 --> 09:12.370 folder, let's import the Ula to quaternion dot ZP and then let's also include still from the Arduino 09:12.370 --> 09:15.810 board messages from the services of this package. 09:15.820 --> 09:20.740 Let's include the quaternion to Euler dot ZP. 09:21.190 --> 09:23.020 Now let's use the first interface. 09:23.020 --> 09:31.840 So the interface for the communication with the Euler to quaternion is the Ula to quaternion and for 09:31.840 --> 09:32.950 the second interface. 09:32.950 --> 09:41.440 So for the communication with the service quaternion to Ula, let's use the quaternion to Ula interface. 09:41.440 --> 09:43.150 And also we need to change. 09:43.150 --> 09:50.510 So we need to set these ones here when we create the Ula to quaternion object, we need to use the Ula 09:50.510 --> 09:57.410 to quaternion interface and the quaternion to ula interface when we create the quaternion to ula object. 09:57.710 --> 09:58.790 So this one. 09:58.790 --> 10:03.980 And also finally we need to change the type also of the interface within the callback function. 10:04.610 --> 10:12.170 So the ula to quaternion callback function receives as input a request message that belongs to the Ula 10:12.170 --> 10:19.520 to quaternion interface and returns a response message that still belongs to the ula to quaternion interface. 10:20.120 --> 10:26.600 Then the quaternion to Euler callback function still receives a request message that this time belongs 10:26.600 --> 10:33.630 to the quaternion to user interface and also returns a response message. 10:33.650 --> 10:37.400 Also this one that belongs to the quaternion to Euler interface. 10:38.220 --> 10:39.360 And now we can move on. 10:39.390 --> 10:42.520 Defining the content of the two callback functions. 10:42.540 --> 10:48.570 And so the logic for the conversion of the orientation between the two conventions, so between Euler 10:48.570 --> 10:50.100 to Quaternion and vice. 10:51.090 --> 10:54.540 Let's start with the Euler to quaternion callback function. 10:54.540 --> 11:03.870 And so let's start by printing an informative message into the terminal with the Rql CPP info stream 11:03.870 --> 11:04.620 function. 11:04.860 --> 11:19.290 So let's use the CPP get log to get the logger of rql cpp and then let's print the message request to 11:19.290 --> 11:22.860 convert user angles. 11:23.280 --> 11:29.320 And now let's print the three Euler angles that were received in the request message. 11:29.340 --> 11:35.520 So the role is in the variable request. 11:36.180 --> 11:38.110 And here this is a pointer. 11:38.110 --> 11:41.440 So let's access to the role. 11:42.430 --> 11:47.140 Then let's also print the pitch. 11:50.060 --> 11:52.520 Still from the request message. 11:52.880 --> 11:54.410 Let's take the pitch. 11:55.010 --> 11:58.490 And then finally, let's take the yo. 12:00.840 --> 12:05.400 And so from the request message, let's take the yaw angle. 12:05.400 --> 12:07.620 So let's print also the yaw angle. 12:07.620 --> 12:10.050 And we want to convert all of these. 12:11.150 --> 12:14.630 Into a quaternion. 12:15.650 --> 12:19.730 So now let's insert the actual logic of the conversion. 12:19.730 --> 12:26.420 And to perform the actual conversion, we can use the TF2 package that is available in Ros two. 12:26.720 --> 12:29.630 So first, let's import this package. 12:29.960 --> 12:40.130 So let's include from the TF2 package the utils modules and now we can use this module to create a new 12:40.130 --> 12:42.560 instance of the quaternion class. 12:42.560 --> 12:51.440 So here from the TF2 namespace, let's create a quaternion and let's call this variable Q. 12:51.950 --> 12:57.470 And this class offers a very useful function that is called set Rpy. 12:57.800 --> 13:05.870 So on the object Q Let's call this set Rpy function, and we can use this function to initialize a quaternion 13:05.900 --> 13:09.110 object based on the three Euler angles. 13:09.110 --> 13:15.000 So based on the three components of the Euler angles, so roll pitch and yaw, and so we can pass to 13:15.000 --> 13:20.070 this function exactly the roll pitch that we received in the request message. 13:20.310 --> 13:27.960 So from the request message, let's take the roll, then the pitch. 13:30.050 --> 13:31.660 And finally also the EU. 13:32.270 --> 13:35.840 Here there is an error, so we don't need a comma. 13:36.750 --> 13:39.090 And here the name is Request. 13:40.690 --> 13:41.920 Okay, now it's fine. 13:42.280 --> 13:45.040 And now we have basically a quaternion object. 13:45.040 --> 13:51.130 So the variable Q that has been constructed based on the three angles. 13:51.130 --> 13:56.950 And so at this point, we can save these four components of the quaternion into the four coefficients. 13:56.950 --> 14:01.330 So into the variable that we need to return into the response message. 14:01.660 --> 14:09.280 So let's access to the response message and we need to assign a value to the variable X and we can use 14:09.280 --> 14:18.190 the variable Q So the quaternion and let's use the get X function, we can do the same for the variable 14:18.190 --> 14:26.710 Y, So let's use the get y function then let's do the same for the variable Z. 14:28.560 --> 14:39.780 Again calling the get Z function and the variable W of the quaternion with the get W. 14:40.890 --> 14:46.530 Finally, once the conversion is done, let's also print another informative message into the console. 14:57.640 --> 15:09.340 So let's use the get logger function to get the logger and let's print the message corresponding. 15:12.630 --> 15:15.190 Mueller quaternion. 15:16.110 --> 15:20.640 And so let's print the four components of the quaternion that are X. 15:22.770 --> 15:26.850 So let's print from the response message the X. 15:27.600 --> 15:31.170 Then let's print the Y. 15:35.030 --> 15:37.280 Then let's print the Z. 15:42.940 --> 15:44.860 And then let's print also the W. 15:52.990 --> 15:57.610 And so with this one, we have all the four components printed into the terminal. 15:58.090 --> 16:00.720 Let's continue with the second callback function. 16:00.730 --> 16:05.350 So the one that we called here quaternion to Euler callback function. 16:05.350 --> 16:12.550 And again, let's start by printing an informative message into the terminal so we can copy this one 16:12.550 --> 16:24.850 in order for avoiding rewriting this code and let's print the message requested to convert quaternion. 16:24.970 --> 16:30.640 And so now let's print the four components of the quaternion that we received this time in the request 16:30.640 --> 16:31.450 message. 16:31.450 --> 16:41.950 So X is the one that we received in the request message in this called X, Then we have Y. 16:45.500 --> 16:47.480 And this is the request. 16:48.230 --> 16:49.030 Why? 16:50.060 --> 16:52.940 Then we have the Z. 17:01.290 --> 17:05.070 And finally, we have the W. 17:09.530 --> 17:10.250 And do this. 17:10.280 --> 17:13.040 We have the four components of the quaternion. 17:14.090 --> 17:20.030 And then now we need to perform the conversion from the quaternion angles to Euler angles. 17:20.360 --> 17:23.660 To do so, we can still use the quaternion class. 17:23.670 --> 17:30.830 And so again, from the Tfcu library, let's create a new quaternion object and let's call this one 17:30.830 --> 17:37.400 Q And this time we use it to create a quaternion from the four coefficients of the quaternion. 17:37.400 --> 17:42.830 So from the four components of the quaternion that we received this time in the request message. 17:42.980 --> 17:48.050 So let's create this quaternion object based on the request message. 17:48.170 --> 17:57.560 So X, Y, z, and W, so these are the four components. 17:57.650 --> 18:00.770 And then again, using the TF2 library. 18:00.770 --> 18:07.550 So TF2 library, we can create a new object of type matrix three by three. 18:07.760 --> 18:14.580 So this one and let's call this matrix M and this object can be initialized from a quaternion. 18:14.580 --> 18:16.560 So from a quaternion object. 18:16.560 --> 18:20.130 And so from the variable that we called Q this class. 18:20.130 --> 18:28.260 So the matrix three by three class offers a very useful function called get r, P, which stands for 18:28.260 --> 18:29.790 Get roll pitch and yaw. 18:30.060 --> 18:34.620 So on the M object, let's call the get r, P. 18:35.550 --> 18:41.310 And so this function here basically returns the roll pitch and the values. 18:41.310 --> 18:48.660 So the Euler angles that we get after the conversion of the quaternion into a rotation matrix. 18:48.660 --> 18:51.720 So basically this matrix is a rotation matrix. 18:51.720 --> 18:56.190 This rotation matrix is constructed based on the value of the quaternion. 18:56.190 --> 19:03.180 And now from the rotation matrix, we can get the roll pitch and so the Euler angles and let's store 19:03.180 --> 19:06.840 these ones directly into the response message. 19:06.930 --> 19:14.960 So into the roll pitch and also into the yaw at the end. 19:14.960 --> 19:17.390 Let's also print another informative message. 19:18.170 --> 19:21.560 So let's still copy this one. 19:22.370 --> 19:23.700 Let's paste it here. 19:23.720 --> 19:25.610 Let's close the parentheses. 19:25.970 --> 19:28.100 And let's print the message. 19:29.390 --> 19:34.000 Corresponding user angles. 19:34.010 --> 19:39.560 And so let's print the URL that is in the response message. 19:39.590 --> 19:40.910 The URL value. 19:41.360 --> 19:45.800 Then let's also print the pitch. 19:47.630 --> 19:50.750 So let's print the pitch variable. 19:51.980 --> 19:55.430 And finally, let's print the yo. 20:00.870 --> 20:03.600 That is still in the response message with this. 20:03.630 --> 20:10.950 We have completed the implementation of our Angles Converter class, so all the class is completed. 20:10.950 --> 20:17.250 We have defined its constructor and also two callback functions that are called when one of the two 20:17.250 --> 20:19.260 services of the class gets called. 20:20.220 --> 20:23.730 Now we only need to change the name of the class to instantiate. 20:23.730 --> 20:31.470 So here in the main function, the class that we want to instantiate is the Angles Converter class. 20:31.650 --> 20:35.540 And now we are ready to install this script and to execute it. 20:35.550 --> 20:41.820 So let's save this file and let's start by modifying the file Cmakelists.txt. 20:42.480 --> 20:53.160 So here, let's include the dependency from the Rql CPP package since we used it in our C plus plus 20:53.160 --> 20:53.760 node. 20:53.880 --> 21:00.090 And also if you haven't followed me in the python lessons, we need to include the Arduino board messages 21:00.090 --> 21:07.140 package as we have used the definition of the Urartu quaternion and quaternion to user interfaces. 21:07.590 --> 21:12.330 Also, as in our C plus plus script, we have used the TF2 library. 21:12.480 --> 21:14.910 Let's also declare the usage of this library. 21:15.360 --> 21:22.600 So let's add a new Findpackage instruction in which we declare the usage of the TF2 package. 21:23.110 --> 21:29.790 Now to install actually a word node, let's add a new abstraction of type add executable. 21:29.800 --> 21:34.810 So here before the python install package, let's add the add 21:37.180 --> 21:42.130 executable instruction and let's name the new node angle 21:44.440 --> 21:45.580 conversion. 21:45.820 --> 21:53.560 And the source code of this file is in the source folder and in the angles conversion dot cplusplus 21:53.560 --> 21:54.070 file. 21:54.370 --> 21:59.140 Then let's also use the instruction arm and target 22:01.090 --> 22:05.140 dependencies to pass to the angle conversion node. 22:05.140 --> 22:08.710 So to this node all the dependencies it needs. 22:08.710 --> 22:17.950 And so the one from the Rql CPP library, from the Arduino bot messages and from the TF2 library. 22:18.400 --> 22:26.400 Finally, we can use an install instruction, so let's put it here in order to install this node. 22:26.520 --> 22:34.380 And so we want to install the target is the angle conversion node. 22:34.410 --> 22:36.870 So let's copy the name of the executable. 22:36.870 --> 22:40.350 Let's paste it here within the install instruction. 22:40.970 --> 22:42.890 And we need to install it. 22:42.890 --> 22:44.390 So the destination. 22:47.340 --> 22:52.200 Is the lib folder and the sub folder that has the same name of the project. 22:52.200 --> 22:53.790 So Arduino but utils. 22:54.450 --> 23:01.680 And so we can use the variable project name to indicate this path. 23:02.620 --> 23:04.690 Let's save also this file. 23:04.690 --> 23:08.810 And as a final step, we need to declare the dependencies of this node. 23:08.830 --> 23:11.750 Also inside the package dot XML. 23:11.770 --> 23:14.980 So here we need to declare the dependency. 23:14.980 --> 23:21.400 So let's add a new dependency and let's declare this one from the CPP library. 23:21.430 --> 23:25.630 Then we need to add a dependency from the Arduino bot messages library. 23:26.260 --> 23:31.240 And also another dependency from the TF two library. 23:31.660 --> 23:33.430 Let's save also this file. 23:33.430 --> 23:39.160 And with this we have completed the creation of our node and also we have instructed the compiler on 23:39.160 --> 23:41.410 how it should make it an executable. 23:41.680 --> 23:46.540 Now we can finally move on to build our workspace and launch our node. 23:46.780 --> 23:54.400 So let's open a new terminal and let's go into the workspace and let's build it with the command called 23:54.580 --> 23:55.090 build. 23:59.240 --> 24:03.510 And when the build is completed, we can open a new window of the terminal. 24:03.530 --> 24:05.880 Here we can source the workspace. 24:05.900 --> 24:08.950 So the file setup dot bash that is in the workspace. 24:08.960 --> 24:10.580 And let's run our node. 24:10.580 --> 24:12.470 So Ros to run. 24:12.950 --> 24:19.220 And from the Arduino bot utils package, let's start the angle conversion node. 24:19.220 --> 24:20.870 So let's press enter. 24:20.870 --> 24:26.930 And upon the node startup we can see already that it informs us that the angle conversion services are 24:26.930 --> 24:31.580 correctly running and are ready to process new conversion requests. 24:31.910 --> 24:32.840 We can verify. 24:32.840 --> 24:42.620 So by opening a new terminal and here we can execute the command Ros2 service list to get the list of 24:42.620 --> 24:45.650 all the services that are currently available in Ros2. 24:45.950 --> 24:51.740 And apart from the ones that were automatically created at the startup of the Node, we can see that 24:51.740 --> 24:57.830 there are the two services that we created and so earlier to Quaternion and quaternion to Euler. 24:58.500 --> 25:04.170 Now we can request the execution of our conversion so we can request so we can call one of these two 25:04.170 --> 25:04.950 services. 25:04.950 --> 25:11.280 And in order to do so, we first need to source the workspace also in this terminal in order for us 25:11.280 --> 25:16.290 to to recognize the message interface that we are going to use for the communication with these two 25:16.290 --> 25:17.160 services. 25:17.160 --> 25:22.650 And so now we can use the command Ros2 service call. 25:22.860 --> 25:29.250 Let's, for example, call the Euler to quaternion service, Ula to quaternion. 25:29.280 --> 25:36.030 Now if we press tab twice, we can already see that Ros two automatically detects that this service 25:36.060 --> 25:42.990 here is accepting ula to quaternion messages that are defined in the Arduino bot Messages library. 25:43.380 --> 25:51.270 So let's type the interface, then let's use the double quotes, then let's press tab twice and let's 25:51.270 --> 25:58.150 type role and then tab and we can see that the Autocompletion is inserting a default message. 25:58.150 --> 26:03.910 So a prototype of the request message that we need to send to the user to quaternion service. 26:04.090 --> 26:15.460 For example, here, let's ask to the service to convert the angles -0.5, then zero and then 1.5. 26:15.460 --> 26:19.960 So this is in radians and we want to convert this one into a quaternion. 26:19.960 --> 26:25.840 So let's press enter and as soon as we do so, we send this request to the server and we can see that 26:25.840 --> 26:29.200 it responds with the corresponding quaternion. 26:29.200 --> 26:34.630 So this is the quaternion that corresponds to these three Euler angles. 26:34.630 --> 26:38.830 So these are the three Euler angles and this is the corresponding quaternion. 26:38.830 --> 26:40.720 And you can also see that the client. 26:40.720 --> 26:46.840 So here in the terminal, we can see that we received the response correctly from the service server. 26:47.290 --> 26:49.960 Let's try to call the second service. 26:50.110 --> 26:54.430 So, Ros, two service call this time. 26:54.430 --> 26:57.190 Let's try to call the quaternion to alert. 26:57.520 --> 26:59.290 Let's press tab twice. 26:59.290 --> 27:04.990 And so we can see that this service is accepting the quaternion to Euler messages. 27:04.990 --> 27:06.730 So the this interface. 27:07.300 --> 27:09.340 So let's use this interface then. 27:09.340 --> 27:10.960 Let's use double quotes. 27:10.990 --> 27:18.970 Let's press tab twice, let's type X, let's press again tab and the Autocompletion of Ros is inserting 27:18.970 --> 27:24.040 an empty prototype of the request message that belongs to this interface. 27:24.040 --> 27:28.450 And now let's set the quaternion that we want to convert to the unit Quaternion. 27:28.450 --> 27:34.390 So to the quaternion that has all the components set to zero except for the last one that we set to 27:34.390 --> 27:34.870 one. 27:35.170 --> 27:36.880 So let's press enter. 27:36.880 --> 27:43.090 And actually we can see that the quaternion corresponds to here the corresponding angles. 27:43.090 --> 27:50.000 So this is the quaternion that we wanted to convert and these are the corresponding Euler angles that 27:50.000 --> 27:53.720 represent the same orientation as this one as this quaternion.