WEBVTT 00:00.050 --> 00:04.820 In this lesson, you will see how you can save all your parameters for a node or even several nodes 00:04.820 --> 00:09.500 inside only one file that you can load at runtime. 00:09.500 --> 00:11.510 And for this we will use YAML. 00:11.510 --> 00:14.870 So that's why we call the files YAML files. 00:14.870 --> 00:17.450 And first let's understand why you need those. 00:17.450 --> 00:20.600 Well here for example you see I have started my. 00:20.630 --> 00:24.170 So I start my number publisher node with two parameters. 00:24.170 --> 00:27.500 But two parameters is a very small amount of parameters for a node. 00:27.500 --> 00:31.490 You will see later on that you can have dozens of parameters for a node. 00:31.490 --> 00:37.490 So if you need to provide those every time with dash p for each parameter, that's going to be quite 00:37.490 --> 00:39.470 long to do that from the command line. 00:39.470 --> 00:44.030 And also what if you want several configurations for several different nodes, etc.? 00:44.030 --> 00:50.720 Well, it's going to be easier to save those values directly inside one file so that you can just load 00:50.720 --> 00:52.940 the file when you start the node. 00:52.970 --> 00:53.270 All right. 00:53.300 --> 00:59.210 So let's um create I'm going to create a folder here in my home directory. 00:59.240 --> 01:02.990 Let's call it YAML params. 01:02.990 --> 01:05.280 This doesn't really matter at all for now. 01:05.430 --> 01:08.580 It's just you create a folder and we're going to put the YAML files. 01:08.580 --> 01:15.540 And then in the next section on launch files we will see how to actually install those YAML files because 01:15.540 --> 01:17.880 we're going to install them inside your workspace. 01:17.910 --> 01:18.060 Okay. 01:18.090 --> 01:20.460 But for now you just put them anywhere. 01:20.460 --> 01:21.360 It doesn't matter. 01:21.360 --> 01:29.820 And let's create a file called let's say number params dot YAML. 01:29.820 --> 01:32.520 So you make sure you have the YAML extension. 01:32.520 --> 01:33.930 And then it could be number. 01:33.960 --> 01:40.380 So number is because it's the number app kind of and params are number config something like that. 01:40.380 --> 01:42.840 And then we're going to edit this file. 01:42.840 --> 01:44.640 So it's just one file I'm going to use Jedit. 01:44.670 --> 01:47.760 You could also open it with VSCode as you want. 01:49.290 --> 01:49.710 All right. 01:49.710 --> 01:52.770 So what do we write inside this file. 01:52.770 --> 01:57.570 Well first of all let's let's run this just in case. 01:57.570 --> 01:59.850 It's always useful to run the node and see what we have. 01:59.850 --> 02:01.890 So ros2 node list. 02:01.920 --> 02:04.920 You see the node is slash number publisher. 02:05.130 --> 02:13.370 So I'm going to come back to my file and I'm going to write the name of the node number publisher. 02:13.970 --> 02:14.120 Okay. 02:14.150 --> 02:17.060 So I start with this and then I put a colon. 02:17.060 --> 02:22.520 I go back to a new line and I'm going to add an indentation of two spaces. 02:22.520 --> 02:31.430 Then I'm going to write Ross underscore underscore parameters and then another column. 02:31.580 --> 02:33.230 So this is super important. 02:33.260 --> 02:36.230 You write the name of the node the complete name. 02:36.230 --> 02:39.200 And then with an indentation we're going to use two spaces. 02:39.230 --> 02:43.610 You write exactly Ross underscore underscore parameters. 02:43.610 --> 02:47.060 That's going to be the same for every node in your application. 02:47.060 --> 02:50.900 Then you go back to a new line and let's add another indentation of two spaces. 02:50.900 --> 02:54.860 So in total here I should have 1234 spaces. 02:54.860 --> 03:02.060 And then I just provide the values for each parameter one by one one in each line. 03:02.060 --> 03:03.080 So what do we have. 03:03.080 --> 03:06.920 You see we have the number parameter and the timer period. 03:06.950 --> 03:09.380 If I do Ross two parameter list. 03:10.370 --> 03:14.580 Basically those are all the parameters that I can give. 03:14.880 --> 03:19.410 So I could also change the use same time so that the simulation time, for example, if you're using 03:19.410 --> 03:24.990 gazebo or stuff like that for simulation, you could decide to start some nodes using the simulation 03:24.990 --> 03:27.270 time, but it's not really useful for now. 03:27.420 --> 03:29.220 And let's go here. 03:29.220 --> 03:34.440 So you see we can do number and timer period. 03:34.440 --> 03:38.610 So let's put number and then a value. 03:38.610 --> 03:44.670 So we make sure to provide a value that is compatible with the data type we have set in the node. 03:45.480 --> 03:51.660 And let's say timer period of 0.7. 03:51.690 --> 03:52.020 Right. 03:52.050 --> 03:56.010 And then you can just add as many parameters as you want okay. 03:56.040 --> 04:01.920 You will see later on it's not uncommon to see files like this which contains more than 100 lines. 04:01.950 --> 04:02.280 All right. 04:02.280 --> 04:03.690 So let's save that file. 04:03.720 --> 04:05.040 Make sure you save it. 04:05.040 --> 04:10.770 And then what we can do I'm going to stop the node and let's start it again. 04:10.770 --> 04:14.400 But this time I'm not going to provide the parameters value directly. 04:14.400 --> 04:19.620 So I will keep Ross ARGs because I'm going to add arguments, but I'm going to add this one. 04:19.620 --> 04:22.830 So let's put it a bit bigger here. 04:23.610 --> 04:28.830 I'm going to add dash dash and then params file. 04:28.830 --> 04:31.560 And I need to put the path to the file. 04:31.560 --> 04:37.200 So it's in my home directory and then YAML params folder. 04:37.200 --> 04:41.760 And that was number params YAML. 04:41.760 --> 04:43.950 You see I can use the autocompletion here. 04:43.950 --> 04:51.210 And if I run that well first it's working and then let's see what we have simply with the Ross two topic 04:51.600 --> 04:53.340 equal number. 04:55.440 --> 04:57.600 You see we publish five every. 04:57.600 --> 05:00.870 So that was I think 0.7 seconds. 05:01.350 --> 05:13.800 We can do Ross two topic h z with number is going to listen to the topic and you see the rate. 05:13.800 --> 05:18.960 So the rate is 1.4 because the period here is 0.7. 05:18.960 --> 05:24.240 That's exactly what we have specified here in the YAML file. 05:24.270 --> 05:24.750 All right. 05:24.750 --> 05:26.190 So you can see this is quite convenient. 05:26.190 --> 05:28.590 You can put as many values as you want here. 05:28.620 --> 05:32.910 You could even create different YAML files for different configurations that you want to load. 05:32.910 --> 05:35.400 And then the command is the same. 05:35.400 --> 05:40.350 You see if you have 1 or 100 parameters the command is going to be the same. 05:40.380 --> 05:46.770 Now this you can do even more with it because we have just the parameters for one node. 05:46.770 --> 05:49.470 But you can have the parameters for as many nodes as you want. 05:49.500 --> 05:56.940 So let's say we want to run two nodes and we're going to rename them number one and number two. 05:56.970 --> 06:00.630 And the two will have different values for the parameters. 06:00.780 --> 06:04.530 So let's rename that one with one. 06:04.530 --> 06:11.160 And then what I'm going to do is simply I'm just going to take this structure and write the same exact 06:11.160 --> 06:15.420 same structure here with a different name here. 06:15.420 --> 06:18.720 So you see you just add the nodes one by one. 06:18.720 --> 06:20.910 Just make sure that you respect the indentation. 06:20.910 --> 06:23.640 We still have the name of the node Ros parameters. 06:23.640 --> 06:26.400 And then let's change the value here. 06:26.550 --> 06:32.100 Let's put three and the time period is going to be 1.0. 06:32.190 --> 06:34.740 All right let's save that. 06:34.980 --> 06:37.830 And now this YAML file we can load it. 06:37.830 --> 06:40.830 And when we load it the node well the node is going to check. 06:40.860 --> 06:44.580 Do I have one line that corresponds to the node name. 06:44.580 --> 06:45.000 Yes. 06:45.000 --> 06:46.860 If yes I apply the parameters. 06:46.860 --> 06:50.100 So let's try this with an example here. 06:50.100 --> 06:52.080 Let's so clear. 06:52.320 --> 06:54.870 Let's run that node. 06:54.870 --> 06:58.740 But I'm going to also rename it because actually let's run it like this. 06:58.740 --> 07:00.480 And let's see what happens. 07:01.260 --> 07:04.500 You see that now we publish. 07:04.500 --> 07:07.380 So we are back to publishing two every one second. 07:07.380 --> 07:08.070 Why is that. 07:08.070 --> 07:12.540 Because we're going to load the YAML file with this node. 07:12.540 --> 07:15.540 But the node is named number publisher. 07:15.960 --> 07:19.560 We check do we have one node here that is named number publisher. 07:19.590 --> 07:20.100 No. 07:20.130 --> 07:21.690 They each have a different name. 07:21.690 --> 07:22.890 So it's not going to be applied. 07:22.890 --> 07:29.290 So the node name must be exactly one of the nodes that you have in the YAML file. 07:29.380 --> 07:35.770 So that's why I'm going to do here dash r and then node. 07:35.860 --> 07:42.490 And I'm going to name it uh number publisher one for example. 07:44.350 --> 07:46.150 So it's been renamed. 07:46.150 --> 07:53.140 And then you can see we have published five every 0.7 seconds. 07:53.170 --> 07:57.730 Because the number of publisher one node here will get all its parameters from that. 07:57.730 --> 08:03.040 And you can see we load a YAML file with two configurations for two nodes. 08:03.040 --> 08:08.230 But this node is only going to take the configuration for its name okay. 08:08.260 --> 08:10.270 It's going to ignore that one. 08:10.270 --> 08:11.950 So then I can start the second node here. 08:11.950 --> 08:18.460 For example to run my what we can start from the Python package or the C plus plus package. 08:18.490 --> 08:23.410 It doesn't matter number publisher and then ros args. 08:23.440 --> 08:31.060 Let's rename it to Number publisher two okay. 08:31.090 --> 08:39.670 Because we want also to have the parameters here and then params file. 08:40.090 --> 08:48.520 And let's provide the path YAML params and number params dot YAML. 08:48.550 --> 08:48.700 Okay. 08:48.730 --> 08:50.110 You can see the command is the same. 08:50.110 --> 08:53.230 We just changed the name of the node. 08:54.220 --> 08:55.690 Okay it is running. 08:55.690 --> 09:03.160 And now here if I do Ros two topic equal with number. 09:05.800 --> 09:09.160 You see we received three and five at different frequencies. 09:09.160 --> 09:17.200 So both nodes are publishing to the number topic with a different number and a different time period. 09:17.200 --> 09:23.500 So you can see you can put several configurations for several nodes inside one file that you load. 09:23.500 --> 09:29.260 And the file is going to check if the name corresponds to one of the nodes that you've provided here, 09:29.260 --> 09:32.680 and if yes, it's going to load the parameters for that node.