WEBVTT 00:00.080 --> 00:02.260 This is activity two of this course. 00:02.270 --> 00:08.840 And in this new activity, what you are going to do is you are going to send some data from the Arduino 00:08.840 --> 00:16.470 to the Raspberry Pi and then process that data on the Raspberry Pi and send back something to the Arduino. 00:16.500 --> 00:16.690 Okay. 00:16.700 --> 00:23.900 So that's something new because what we've done before is to just send data directly from one side to 00:23.900 --> 00:29.150 the other one or to send some data from the Raspberry Pi and respond from the Arduino. 00:29.180 --> 00:34.640 Here we initiate the communication from the Arduino and we respond from the Raspberry Pi. 00:34.640 --> 00:38.780 But as you will see, that is not more complicated than what we have done before. 00:38.810 --> 00:39.290 Okay. 00:39.290 --> 00:44.060 So if you correctly understood the previous things, that's going to be okay for you. 00:44.090 --> 00:46.340 So what is your challenge? 00:46.340 --> 00:51.060 Your challenge is to send some temperature from the Arduino to the Raspberry Pi. 00:51.080 --> 00:56.420 So the temperature here, we don't have a temperature sensor and I'm not going to use one. 00:56.420 --> 00:58.630 We are just going to fake some temperatures. 00:58.640 --> 00:58.850 Okay. 00:58.850 --> 01:00.030 For this example. 01:00.030 --> 01:05.880 And so you send the temperature from the Arduino and then you're going to check this temperature in 01:05.880 --> 01:08.310 the Raspberry Pi in the Python program. 01:08.310 --> 01:14.820 And if this temperature is lower than a certain threshold, you are going to power on the Led. 01:14.970 --> 01:17.040 So the built in led on the Arduino. 01:17.070 --> 01:22.380 If the temperature is above the threshold, you are going to power off the Led. 01:23.010 --> 01:34.560 So on the Arduino side is to send temperature and then on parallel is to receive data from sale and 01:34.800 --> 01:38.580 power on or off the Led. 01:39.840 --> 01:46.740 So here I have given you some code structure here you can already use. 01:46.770 --> 01:51.510 So basically to send the temperature, let's say we want to send the temperature every one second. 01:51.510 --> 01:57.070 So every 1000 milliseconds, we are not going to use the delay because if we use the delay in the while 01:57.120 --> 02:02.610 loop and then we try to receive data from cell, well, the delay is going to block the program and 02:02.610 --> 02:06.030 we are going to receive data from cell with some delay, actually. 02:06.030 --> 02:06.200 Okay. 02:06.210 --> 02:12.330 So if you block the program for one second, you're going to have a delay of maximum one second to receive 02:12.330 --> 02:13.290 data from the cell. 02:13.290 --> 02:14.310 And you don't want that. 02:14.310 --> 02:17.190 You want to receive data as soon as it is here. 02:17.220 --> 02:17.730 Okay. 02:17.730 --> 02:21.630 So what we're going to do is we're going to do some kind of multitasking. 02:21.630 --> 02:26.070 And as a recap, I have shown you a structure here for multitasking. 02:26.070 --> 02:28.080 So basically that's very simple. 02:28.110 --> 02:28.310 Okay? 02:28.320 --> 02:35.280 You create so for an action you want to do, you create this variable unsigned long with the last time 02:35.280 --> 02:40.000 you have done the action, you initialize it to zero or millis doesn't matter. 02:40.000 --> 02:46.840 And then you have an action delay, which is the delay you want to spend between two actions that you 02:46.840 --> 02:47.020 do. 02:47.020 --> 02:49.480 So here, for example, 1000 millisecond. 02:49.840 --> 02:56.350 Then in the while loop you get the current time with Millis and then you check the difference between 02:56.350 --> 02:57.070 the current time. 02:57.070 --> 03:00.070 So the time now and the last time you have done the action. 03:00.100 --> 03:05.950 This gives you a duration and if this duration is greater than the action delay, then you can do the 03:05.950 --> 03:06.400 action. 03:06.400 --> 03:13.240 And of course you update the last time the action was done to the current time and then you do the action. 03:13.240 --> 03:18.940 So here you can select a random number for the temperature and send it to the cell. 03:19.090 --> 03:29.020 And here on parallel you can do so read cell basically this. 03:29.030 --> 03:30.310 So this is going to be very fast. 03:30.310 --> 03:31.360 This is going to be very fast. 03:31.360 --> 03:33.550 So it's going to go very, very, very fast. 03:33.550 --> 03:39.340 So it's just like if you were doing some kind of multithreading on your Arduino and to get the random 03:39.340 --> 03:42.550 number, I have given you the random function here of the Arduino. 03:42.550 --> 03:47.410 So basically, if you want a random number between, for example, five and 25, you just do random 03:47.410 --> 03:49.300 five comma 25. 03:49.330 --> 03:53.350 Okay, I'm going to use Celsius degrees here, but doesn't really matter. 03:53.350 --> 03:57.340 So if you do this, the random number will be between 5 and 25. 03:57.370 --> 04:03.400 Now on the Raspberry Pi, what you're going to do is read Serial, okay? 04:03.580 --> 04:05.740 And then you're going to receive some temperature. 04:05.740 --> 04:10.450 So receive number and then process that number. 04:10.450 --> 04:18.850 So basically you're going to say if number is, for example, lower than 15, you're going to have power 04:18.850 --> 04:23.590 on the LCD and else you are going to power off the LCD. 04:23.860 --> 04:32.590 So in your own kind of void loop on the Raspberry Pi, you first read from Serial, and once you have 04:32.620 --> 04:37.060 gotten some data, you process the data and you write directly to the Arduino. 04:37.210 --> 04:37.750 Okay? 04:37.960 --> 04:44.770 And well, what I'm going to do is I'm going to actually get the code from activity one. 04:44.800 --> 04:46.030 I'm going to get that. 04:46.030 --> 04:49.300 I'm not going to rewrite everything in this case. 04:49.300 --> 04:50.350 Why is that? 04:51.010 --> 04:54.550 Because simply we are going to need to use this. 04:54.580 --> 05:01.240 We are going to need to initialize the communication with the exact same code and then we have the exact 05:01.240 --> 05:03.190 same while true structure. 05:03.190 --> 05:04.900 I'm just going to remove all of that. 05:04.900 --> 05:12.040 Let's put bus here and while this code is going to be the same, okay, for the previous ITV and this 05:12.040 --> 05:12.220 one. 05:12.220 --> 05:20.740 So I'm not going to write it every time because we have basically here 14 lines of code that are identical. 05:20.800 --> 05:21.370 All right. 05:21.370 --> 05:25.180 And now we'll see you in the next lesson for the solution.