WEBVTT 00:00.110 --> 00:04.730 And this is the second part for the activity five for the second challenge. 00:04.730 --> 00:09.110 In this challenge we are focusing on the LED panel node. 00:09.110 --> 00:14.780 So let's go back to the code and we can leave this here and go to LED panel. 00:14.780 --> 00:16.790 As you can see we have. 00:16.790 --> 00:22.490 So we are setting three LEDs with default state to zero which means turning off the LED. 00:22.490 --> 00:27.290 And what we want to be able to do is to provide a different configuration for this array. 00:27.290 --> 00:28.460 When we start the node. 00:28.460 --> 00:38.300 So we can add a parameter for that self declare parameter and let's name it led state. 00:38.420 --> 00:39.200 Okay. 00:39.290 --> 00:42.170 Could be led initial states. 00:42.200 --> 00:43.580 I'm just going to leave it like this. 00:43.580 --> 00:45.170 And the default value. 00:45.200 --> 00:50.330 Well as I told you you could use basic data types like strings integer doubles. 00:50.330 --> 00:53.690 But you can also use lists of those data types. 00:53.690 --> 00:57.770 So the default value can be a list of integers. 00:58.010 --> 00:58.250 All right. 00:58.250 --> 01:01.250 So I just put the same value I used before. 01:01.850 --> 01:09.630 So what I'm saying here is that I'm creating an led state state's parameter of data type list of integer 01:09.630 --> 01:12.570 and it contains three zeros. 01:12.570 --> 01:19.710 And then what I can do is LD states is equal to self dot get parameter. 01:20.160 --> 01:25.590 The name of the parameter is led states and then dot value. 01:25.620 --> 01:27.030 So that's it for the parameter. 01:27.060 --> 01:28.890 Then let's check that everything is correct. 01:28.890 --> 01:30.750 So where do we use that. 01:30.780 --> 01:33.270 You see we publish this on a topic. 01:33.270 --> 01:34.530 So all good. 01:34.830 --> 01:44.070 And then in the callback set LED we also check that the LED number is not outside of the list. 01:44.070 --> 01:47.640 And because we use this syntax we just check the length. 01:47.640 --> 01:52.530 So it's quite dynamic, meaning that if the list contains three elements it's going to work. 01:52.530 --> 01:56.280 But if the list contains five elements, it's also going to work. 01:56.280 --> 01:59.400 So we check that the code is still working correctly. 01:59.400 --> 02:02.550 And yes, I'm going to save that. 02:02.550 --> 02:04.050 Let's go back to the terminal. 02:04.050 --> 02:06.240 And I have used Simulink installed previously. 02:06.240 --> 02:07.980 So I can just run the node. 02:09.210 --> 02:13.070 So Python package LED panel. 02:13.070 --> 02:17.000 Let's just run it like this and let's do a Ros two. 02:17.420 --> 02:22.910 So Ros two param list to see that we have the parameter okay. 02:22.910 --> 02:31.070 And then Ros two param get LED panel and LED states. 02:32.720 --> 02:38.420 So you see integer values which means a list of integer zero zero and zero. 02:38.420 --> 02:39.620 So that's the initial state. 02:39.620 --> 02:45.740 That's the configuration for our LED panel we say that basically we have three LEDs powered off. 02:45.740 --> 02:52.190 And I also have a topic eco LED states or something like that LED panel state. 02:52.190 --> 02:54.860 And that's going to be every five second. 02:55.010 --> 02:57.440 You see we have the LED states here. 02:57.470 --> 02:59.540 Now let's provide something different. 02:59.540 --> 03:04.610 Let's say that you want to start this LED panel node, but you have five LEDs. 03:04.610 --> 03:12.440 So let's do Ros args dash p LED states. 03:13.070 --> 03:17.310 And then let's provide a list like that. 03:17.850 --> 03:18.840 Zero. 03:18.960 --> 03:19.890 Zero. 03:19.920 --> 03:20.730 Zero. 03:20.760 --> 03:21.390 Size three. 03:21.420 --> 03:21.930 That's four. 03:21.930 --> 03:23.190 And that's five. 03:24.780 --> 03:25.050 Okay. 03:25.080 --> 03:26.670 And you can see we have an error. 03:26.670 --> 03:29.340 Because you cannot pass an array like that. 03:29.340 --> 03:31.710 You need to also put some quotes. 03:34.110 --> 03:34.620 Okay. 03:34.650 --> 03:36.270 Because you have some spaces as well. 03:36.270 --> 03:40.800 So you need to put some quotes and then it should work. 03:40.800 --> 03:42.810 So what do we have on the topic. 03:44.220 --> 03:45.450 Let's see. 03:45.480 --> 03:46.530 Let's wait a bit. 03:46.530 --> 03:53.280 And we have you see now on the topic we have five entities. 03:53.400 --> 03:56.910 And the parameter also has five values. 03:56.910 --> 03:58.740 So you see it's quite powerful. 03:58.770 --> 04:03.000 You could have an LED panel node with as many LEDs as you want. 04:03.030 --> 04:07.440 So you could first set up the LEDs I don't know, let's say you have between 1 and 10 LEDs on your panel, 04:07.440 --> 04:10.530 and then you start the node with how many LEDs you want to start. 04:10.530 --> 04:16.710 And one thing to pay attention here is let's say I start this again and I provide the value seven here. 04:18.150 --> 04:19.990 And it's still working. 04:20.020 --> 04:20.200 Okay. 04:20.230 --> 04:24.250 Because I didn't check anything in the code, so I'm going to get the value seven. 04:24.280 --> 04:31.060 Even though I have stated in the code that I only want values that are 0 or 1. 04:31.090 --> 04:31.270 Okay. 04:31.300 --> 04:36.400 As you can see, when I get a request here from the service, I check if the value is 0 or 1. 04:36.400 --> 04:43.930 So what you can do when you have parameters is you can also decide to check if the value is correct, 04:43.930 --> 04:45.940 so you can decide to trust or not. 04:45.970 --> 04:50.230 What you get from the command line or from the YAML files okay. 04:50.590 --> 04:58.480 So usually in well in most applications usually you know that you give values that are correct, okay. 04:58.510 --> 05:05.530 Because you are the one writing the code and you are also the one writing the parameters when you start 05:05.530 --> 05:06.190 the node. 05:06.250 --> 05:06.520 Okay. 05:06.550 --> 05:08.530 So here you would not do that. 05:08.530 --> 05:11.470 You would provide a 0 or 1. 05:11.470 --> 05:16.960 But if you want you could also validate the data before you actually use it in the code. 05:16.990 --> 05:17.380 All right. 05:17.380 --> 05:19.630 So that's it for this parameter. 05:19.630 --> 05:23.590 But then we also want to add this inside a YAML file. 05:23.590 --> 05:30.410 So let's go back here and I'm going to go inside my YAML params folder. 05:30.530 --> 05:32.780 Again you can put it anywhere you want. 05:32.810 --> 05:35.120 We're going to install it in the next section. 05:35.120 --> 05:38.060 But for now it doesn't matter at all as long as you know where it is. 05:38.630 --> 05:44.270 And I'm going to create a LED config for example dot YAML. 05:44.300 --> 05:45.770 So the name doesn't matter. 05:45.770 --> 05:50.780 Just make something that has some sense and YAML extension. 05:51.440 --> 05:55.130 And let's do a git led config. 05:55.130 --> 05:58.400 So let's start with the name of the node. 05:58.400 --> 06:01.670 The name of the node we see is going to be led panel. 06:01.670 --> 06:02.960 I'm not going to rename it. 06:02.960 --> 06:16.310 So slash LED panel new line two spaces rows underscore underscore parameters and then two more spaces. 06:16.340 --> 06:17.300 What do we have. 06:17.330 --> 06:19.460 We have led state. 06:19.790 --> 06:23.690 And let's say 0000. 06:23.720 --> 06:25.370 I'm going to put four LEDs here. 06:25.400 --> 06:25.790 All right. 06:25.790 --> 06:27.770 And I just have one parameter. 06:27.770 --> 06:29.650 So that's it. 06:29.680 --> 06:29.950 All right. 06:29.980 --> 06:30.760 So we have three lines. 06:30.760 --> 06:33.220 The first one is for the name of the node. 06:33.310 --> 06:38.980 Then the parameters for every node and then the list of parameters one in each line. 06:38.980 --> 06:40.420 Let's save the file. 06:40.690 --> 06:47.740 And now what we can do I can start my LED panel node again. 06:47.740 --> 06:56.170 But instead of providing the parameters like that I can do so ros args and then params file. 06:56.230 --> 06:59.470 And let's go to the. 06:59.590 --> 07:06.730 So let's put the path YAML params and led config.yaml. 07:08.140 --> 07:12.670 All right it is started and we can just verify that very quickly. 07:13.630 --> 07:15.640 You see we have four values. 07:15.640 --> 07:17.440 So that was correctly working. 07:17.440 --> 07:29.440 And if I echo the topic we will have here you see we have four values which means that the value from 07:29.440 --> 07:34.510 the YAML file was taken and is now active in the code.