WEBVTT 00:00.420 --> 00:05.700 Let's now see how to combine together the two sides of cellular communication. 00:06.330 --> 00:11.370 And we're going to start from the previous program where we send something from the Raspberry Pi to 00:11.370 --> 00:12.000 the Arduino. 00:12.270 --> 00:16.640 What we are going to do is we're going to send back the message to the Raspberry Pi. 00:16.770 --> 00:18.750 We have something that we are the kit. 00:18.780 --> 00:21.330 OK, so this program is already working. 00:21.510 --> 00:24.330 If you don't have this, please go back to the previous view. 00:24.630 --> 00:28.920 So what I'm going to do is I'm going to add something to the message here. 00:29.310 --> 00:36.480 For example, a counter that we're going to increase every time so we can see a progression on the message. 00:37.350 --> 00:44.490 So I'm going to create here and global viral and counter is equal to zero. 00:44.500 --> 00:46.050 Let's initialize it to zero. 00:46.830 --> 00:56.250 And so once we receive the message, what we are going to do is to do this, each is equal to so message. 00:56.970 --> 00:59.340 Plus, let's add a space. 01:00.150 --> 01:06.330 Plus, let's add to counter the counter is an integer, so we're going to need to convert it to a string. 01:06.330 --> 01:09.270 So we use string we've come to. 01:10.720 --> 01:18.100 So if we receive hello from Raspberry Bay, we're going to know transform it to hello from Raspberry 01:18.100 --> 01:21.160 Pi Zero and then one two three four two. 01:21.640 --> 01:28.210 So of course, if we want to increase the content we encounter plus plus after we have used it and then, 01:28.510 --> 01:31.210 well, here we receive some data. 01:31.810 --> 01:37.490 We transform the data and we can do cellular print elements, do and print. 01:37.540 --> 01:40.600 Then another time we've missed each. 01:41.380 --> 01:41.750 All right. 01:41.770 --> 01:44.460 And let's run that on the audio. 01:44.510 --> 01:45.550 It's this. 01:48.140 --> 01:53.690 Don't applauding and actually before we write anything on the Raspberry Pi side, we can already debug 01:53.690 --> 01:59.060 this program because, yeah, we would be able to see the message we've printed and which means that 01:59.270 --> 02:01.850 we can do with the say and monitor. 02:02.030 --> 02:02.270 OK. 02:02.570 --> 02:07.820 So I opened a site in moneyto and I'm going to send the stream, let's say ABC. 02:08.930 --> 02:12.710 And you can see I have ABC zero eight. 02:12.920 --> 02:15.290 I sent another stream, a random stream. 02:16.370 --> 02:18.320 I have one a hello. 02:18.770 --> 02:20.570 Hello to hello. 02:20.900 --> 02:21.260 Three. 02:22.040 --> 02:24.870 So we know that the original programs correct. 02:24.870 --> 02:25.520 Keep walking. 02:26.090 --> 02:27.590 So we send this train. 02:27.860 --> 02:28.670 We also have. 02:28.760 --> 02:29.560 So that's very important. 02:29.570 --> 02:31.970 We have new lines with New Line. 02:32.570 --> 02:34.880 Was going to add a backslash thing at the end. 02:35.060 --> 02:36.230 OK, and new line character. 02:36.650 --> 02:40.310 If you want to add nothing, you go with no line ending, but I'm going to keep new name. 02:40.850 --> 02:46.250 So you send a stream and you received a stream space and we will counter it increases every time. 02:46.850 --> 02:47.240 All right. 02:47.600 --> 02:50.240 So no, that we know it's working on the other side. 02:50.270 --> 02:52.100 Let's go to the Raspberry Pi sign side. 02:52.490 --> 02:53.180 And here what? 02:53.180 --> 02:55.070 We're going to send a message to the area. 02:55.700 --> 02:57.680 So let's keep yellow from Raspberry Pi. 02:57.950 --> 02:58.370 Great. 02:58.910 --> 03:01.670 And then we're going to receive this message. 03:02.390 --> 03:08.090 So as you can see here, we directly read the string we modified and we send it back. 03:08.090 --> 03:10.010 So it should be almost immediate. 03:10.130 --> 03:10.430 OK. 03:10.820 --> 03:14.840 So I'm going to stay just off to the right and then read the string. 03:15.260 --> 03:20.930 But before that, as let's see a way to be sure, we have received the data I'm going to do. 03:22.010 --> 03:33.290 While Sara notes in waiting is a lower or equal than zero, which means that here we check if we have 03:33.290 --> 03:36.350 received some byte if this is equal to zero. 03:36.890 --> 03:38.610 Well, I'm going to do time. 03:38.630 --> 03:39.920 Don't sleep. 03:41.270 --> 03:44.030 0.01 OK, so we're going to wait. 03:44.360 --> 03:52.070 Zero point zero one Second in an infinite loop as long as we haven't received any data once we have 03:52.070 --> 03:53.540 received data. 03:53.960 --> 03:56.720 What I'm going to do is I'm going to do Sara. 03:56.780 --> 04:00.830 So basically, the way loop is going to exit, I'm going to do set a red line. 04:03.290 --> 04:08.840 Don't decode we've UTF eight. 04:10.430 --> 04:21.950 But a trick, and I'm going to put that inside a viable named, let's say a response is equal to that 04:21.980 --> 04:25.910 and then let's sprint response. 04:26.990 --> 04:32.960 OK, so every one second we send a message to the other know we wait until we receive something. 04:33.680 --> 04:35.960 We read that thing we've printed. 04:36.470 --> 04:37.970 We go back to the beginning. 04:38.660 --> 04:43.760 What you can see on the rise of the right and I'm coming to that know is we also have a timeout is equal 04:43.760 --> 04:47.060 to one here when we open the cell communication. 04:47.630 --> 04:53.030 So basically, we set a one second timeout, the same that we have under Arduino. 04:53.030 --> 04:57.140 But on the, you know, we don't need to write it to have one second, if you don't. 04:57.140 --> 05:00.980 But this it means you have infinite timeout. 05:01.280 --> 05:04.400 And the timeout is actually not the timeout for everything. 05:04.550 --> 05:07.640 It's a timeout for when you read, we said. 05:07.970 --> 05:13.310 So when you use this red line, basically it's going to do the same thing as here. 05:13.610 --> 05:18.790 He's going to read the next line, OK, until basically this backslash and character. 05:19.490 --> 05:25.730 So if you receive something that ends with a backslash and character, it's going to return immediately. 05:26.210 --> 05:30.110 If not, it's going to wait at least one second. 05:30.410 --> 05:36.830 So normally, if you correctly put backslash in with print L.A., you should not have any timeout problem. 05:37.010 --> 05:40.400 But I have still included it here just in case. 05:40.400 --> 05:46.070 So we don't have an infinite timeout that's going to completely block our code if we have one error 05:46.220 --> 05:47.450 coming from the Arduino. 05:48.110 --> 05:48.380 OK. 05:48.500 --> 05:51.860 The Arduino is correctly running the codes. 05:52.070 --> 05:54.170 Let's bring the cool in the Raspberry Pi. 05:56.960 --> 05:58.570 Say, OK, send a message. 05:58.850 --> 05:59.300 You can see. 05:59.330 --> 06:02.880 And hello from Raspberry Pi one two three four. 06:02.900 --> 06:03.860 Etc., etc.. 06:04.160 --> 06:04.700 Voice control. 06:04.720 --> 06:05.090 See? 06:08.020 --> 06:14.560 And you can see it is currently working, so now you have a bi directional communication, so great. 06:14.800 --> 06:21.400 Now you can communicate from Raspberry Pi to Arduino and from other the Raspberry Pi in the same program. 06:21.580 --> 06:28.960 And so to conclude on that, the examples we have seen here are actually super super simple, OK, but 06:28.960 --> 06:34.960 they are good to make you familiar with cellular in the following in the course, you will practice 06:34.960 --> 06:41.920 more real applications so that you can better understand how to use cellular in a more complex situation. 06:42.460 --> 06:48.820 There are so many possibilities, and so instead of listing them all here, which is going to be quite 06:48.820 --> 06:55.660 boring, well, you will simply discover them while going through the course and through the activities.