WEBVTT 00:00.080 --> 00:05.960 Now that you have seen renaming and remappings in this lesson, you will learn how to set parameters 00:05.960 --> 00:09.080 values to your nodes inside a launch file. 00:09.080 --> 00:15.590 We will first set the parameters one by one, and then load them directly from a YAML file that we will 00:15.590 --> 00:19.220 also install inside the Myrobot bringup package. 00:19.220 --> 00:20.390 Let's get started. 00:20.390 --> 00:28.070 So if you remember from the command line so I can stop all that from the command line when we start 00:28.070 --> 00:31.040 a node with Ros to run, we have also Ros args. 00:31.040 --> 00:34.730 And then we can do dash p param name. 00:34.790 --> 00:37.310 And that's going to be value okay. 00:37.340 --> 00:40.580 So how do we add this inside a launch file. 00:40.580 --> 00:44.750 Well let's go back and well where do we have parameters. 00:44.750 --> 00:48.290 Actually we don't have any parameter in my number counter. 00:48.290 --> 00:52.670 So I'm going to well we have the default ones but we haven't added ones in the code. 00:52.700 --> 00:54.740 I'm going to leave this one like that. 00:54.740 --> 00:58.100 But in number publisher we have two parameters okay. 00:58.130 --> 01:01.910 So if I come back to the code number publisher? 01:02.690 --> 01:06.650 You see, we have the number parameter and the timer period. 01:07.610 --> 01:09.200 So let's add those parameters. 01:09.200 --> 01:10.880 Let's add values for those. 01:10.880 --> 01:11.780 Where do we do this. 01:11.810 --> 01:14.060 Well you do this inside the node tag. 01:14.060 --> 01:18.560 So you need to open and close the node tag if it hasn't been done yet. 01:18.560 --> 01:22.970 And then we can add a param tag. 01:23.000 --> 01:23.270 Okay. 01:23.300 --> 01:26.330 So we have the remappings and then we have the param tags. 01:26.330 --> 01:32.780 And for each param tag you have name and value arguments. 01:33.440 --> 01:37.100 So quite easy here name is going to be number. 01:37.100 --> 01:40.580 And the value let's say six. 01:40.580 --> 01:44.450 And that's going to set the parameter number with the value six. 01:44.450 --> 01:47.570 When you start the node with the launch file okay. 01:47.690 --> 01:52.940 And if you want to add more params you add another param tag name. 01:52.940 --> 01:56.690 That one is timer period. 01:56.690 --> 01:59.100 Make sure it's the correct name value. 01:59.220 --> 02:05.130 Let's say 1.5 seconds and make sure you provide the correct data type as well. 02:05.160 --> 02:05.610 All right. 02:05.610 --> 02:07.500 And that's it for the parameters here. 02:07.500 --> 02:11.430 Let's save and then let's build again. 02:11.700 --> 02:17.640 So let's do a click on build let's source. 02:18.960 --> 02:24.630 And let's start the number app launch dot XML. 02:24.630 --> 02:28.260 So you see to start and to test launch files is quite easy. 02:28.260 --> 02:34.830 It's quite convenient to have one terminal here where you just build source and launch in that order. 02:36.780 --> 02:40.230 So okay it's working. 02:40.230 --> 02:44.730 And now we can just check actually what we have on the number topic. 02:44.730 --> 02:48.810 Ross two topic equal number. 02:50.700 --> 02:52.800 Actually it's not a number. 02:52.800 --> 03:00.630 It's it's my number because if you remember, we have remapped the topic. 03:01.470 --> 03:05.160 So what do we have on my number? 03:05.460 --> 03:08.850 We have six published every word. 03:08.880 --> 03:12.720 You can check the frequency but it's going to be every 1.5 second. 03:12.990 --> 03:13.800 Great. 03:13.800 --> 03:26.460 And we can also do rows to param list and see that we have plus two param get with my number publisher 03:27.510 --> 03:29.100 and number. 03:30.720 --> 03:32.040 We have six. 03:32.700 --> 03:42.060 And for the time period we have 1.5 which is exactly what we have set in the launch file. 03:42.090 --> 03:43.980 Okay so it's quite easy now. 03:44.010 --> 03:47.250 Well that's good if you have only a few parameters. 03:47.250 --> 03:48.990 But let's say you have many parameters. 03:48.990 --> 03:53.760 And let's say you've already created a YAML file or you want to create a new one. 03:53.760 --> 03:56.200 Where are you going to put your YAML files? 03:56.200 --> 04:04.420 Because for now, if you remember, we have just added I have a YAML params folder here in my home directory, 04:04.420 --> 04:10.240 and we have the two YAML files that we have created here number params and led config. 04:10.270 --> 04:16.780 Well, now that we have this bringup package here, we're not just going to create the YAML files anywhere 04:16.780 --> 04:21.610 in our computer, we're going to add them inside the package. 04:21.910 --> 04:24.970 And for that I'm going to go back to. 04:25.000 --> 04:29.560 So let's go to our My Robot Bringup package. 04:29.680 --> 04:32.110 And we have a launch folder. 04:32.110 --> 04:38.050 I'm going to create a new one that will usually we name it config. 04:38.080 --> 04:39.610 It could be params. 04:39.640 --> 04:40.990 It could be whatever you want. 04:41.260 --> 04:43.840 But usually config is a quite common name. 04:44.050 --> 04:46.870 And now you have a launch and a config folder. 04:47.230 --> 04:48.430 Okay it's here. 04:48.430 --> 04:52.090 And in this config folder you are going to add your YAML files. 04:52.120 --> 04:55.360 And there's one thing we need to do to set up this config folder. 04:55.360 --> 05:03.370 We go back to the cmakelists.txt and you see here we say to install the launch folder inside this directory. 05:03.400 --> 05:07.540 After launch you're going to put a space and then config. 05:07.540 --> 05:11.440 So now we say to install the launch folder and the config folder. 05:11.440 --> 05:17.620 So any new folder that you add in the Myrobot bringup that you want to install, you just add a space 05:17.620 --> 05:19.510 and then you put the name of the folder. 05:19.510 --> 05:22.630 So make sure you add the config folder here. 05:22.660 --> 05:23.680 Very important. 05:23.950 --> 05:27.400 And then let's add a new YAML file. 05:27.400 --> 05:32.560 So let's call it number app dot YAML for example. 05:32.560 --> 05:34.480 And now let's provide the parameters. 05:34.480 --> 05:41.920 So we want to add the number parameter and the timer parameter for the my number publisher okay. 05:41.950 --> 05:44.320 You see the name must match. 05:45.100 --> 05:49.810 So I'm going to write my number publisher. 05:51.190 --> 06:01.330 And then two spaces Ross underscore underscore parameters and then more spaces here number. 06:02.050 --> 06:10.630 Well let's use the same values and timer period 1.5 okay I'm going to save that file. 06:10.630 --> 06:14.110 So this is what we've seen on the previous section on parameters. 06:14.110 --> 06:18.400 If you have some doubt you can come back to the to the lesson on YAML files. 06:18.400 --> 06:25.420 And now that we have this YAML file here inside the config folder, we can load it directly here inside 06:25.420 --> 06:26.320 this launch file. 06:26.320 --> 06:27.790 And how do we do this. 06:27.790 --> 06:31.480 Well first I'm going to actually comment those lines. 06:31.480 --> 06:34.720 So here I use control shift and slash. 06:34.750 --> 06:39.490 I'm going to comment those lines so that I don't write the parameters manually. 06:39.490 --> 06:42.010 But I still leave the code so that you can see it. 06:42.040 --> 06:47.410 How to say that we want to load those parameters from this launch file. 06:47.620 --> 06:55.310 Well you are going to add a param tag as well, but instead of name and value you are going to write 06:55.310 --> 06:59.450 from, and that's going to be the path to the YAML file. 06:59.450 --> 07:00.590 And how do we find this? 07:00.620 --> 07:02.120 Well, we're going to use the function. 07:02.120 --> 07:09.650 We have used the same function in the in this XML file to include another launch file we are going to 07:09.680 --> 07:10.340 use. 07:10.340 --> 07:20.060 So dollar sign parentheses bind pkg share and the name of the package my robot bring up. 07:20.060 --> 07:21.440 So it could be from this package. 07:21.440 --> 07:23.210 It could be from another package. 07:23.210 --> 07:26.030 And then slash where is the file. 07:26.090 --> 07:33.320 Well in config slash number app dot YAML okay. 07:33.320 --> 07:35.090 And then we finish. 07:35.090 --> 07:36.290 We close the tag. 07:36.290 --> 07:42.320 So once again find pkg share with the package name in parentheses with a dollar sign. 07:42.410 --> 07:44.720 And then slash the path. 07:44.720 --> 07:48.350 So the relative path here to the YAML file. 07:48.410 --> 07:50.870 And that's going to load the YAML file. 07:50.870 --> 07:58.610 And in this YAML file we have you see parameters for my number publisher which is going to work with 07:58.610 --> 07:58.940 this. 07:58.940 --> 08:04.100 And so you see if you have 200 parameters then you add your 200 parameters here. 08:04.490 --> 08:07.550 And your launch file is still super small. 08:07.580 --> 08:08.750 Let's save that. 08:08.750 --> 08:13.490 And let's uh, let's just test it. 08:14.300 --> 08:24.920 So we build again, we source again and we run again and it's working I guess. 08:24.920 --> 08:26.120 No surprise. 08:27.410 --> 08:31.040 Time period and number, you see still the same. 08:31.040 --> 08:34.580 But this time we load them from the YAML file. 08:35.510 --> 08:42.830 And here is what you have to do in case you have to add parameters inside the Python launch file you 08:42.830 --> 08:43.910 see inside the node. 08:43.910 --> 08:51.870 Here we have another parameters argument, which is a list, but this time we use curly brackets. 08:51.900 --> 08:55.680 Okay, so make sure that you don't make the confusion here. 08:55.680 --> 09:00.420 So this is like a dictionary but this is a tuple for remappings. 09:00.450 --> 09:00.630 Okay. 09:00.630 --> 09:01.710 So not the same thing. 09:01.710 --> 09:05.550 And then you can just put one parameter on each line just like that. 09:05.580 --> 09:07.290 So not too complicated. 09:07.500 --> 09:08.970 And that's the code. 09:08.970 --> 09:12.990 If you want to load a YAML file inside a Python launch file. 09:12.990 --> 09:15.060 So we are still using the same YAML file. 09:15.090 --> 09:16.500 Okay from this package. 09:16.530 --> 09:24.870 But you can see you need to import get package shared directory from element index python packages and 09:24.870 --> 09:25.920 then import OS. 09:25.920 --> 09:30.570 You can have the path here for the parameter config. 09:30.570 --> 09:33.270 And then you can add the parameter here just like that. 09:33.270 --> 09:36.300 So just in case that's how you do it in Python. 09:36.300 --> 09:39.750 But of course I recommend you do that in XML. 09:39.750 --> 09:43.890 You just have to remember find pkg share and that's it.