Scilab/C4/Calling-User-Defined-Functions-in-XCOS/English-timed

Time	Narration
00:01	Welcome to the spoken tutorial on Calling user-defined functions in Xcos.
00:07	In this tutorial we will learn:
00:09	* To write a squaring function in Scilab
00:12	* To use the scifunc block in Xcos
00:15	* To use MUX block to draw multiple plots
00:19	* To call functions having multiple inputs and outputs.
00:24	Ubuntu 12.04 is the operating system used with Scilab version 5.3.3 installed.
00:32	You should have basic knowledge of Scilab,
00:35	basic knowledge of Xcos.
00:38	If not, for relevant tutorials, please visit spoken hyphen tutorial dot org.
00:44	Start Scilab on your computer.
00:47	In the Scilab console, type editor and press Enter.
00:53	Then type the following code:
00:55	function space y is equal to squareit open bracket a close bracket.
01:07	Press the Enter key and type:
01:10	y is equal to a raise to 2
01:14	put a semicolon in the end.
01:17	The function has one input variable a and one output variable y.
01:24	The name of the function is squareit.
01:27	This function will do the job of squaring the variable a.
01:31	It will store the result in y.
01:34	Let us save this file in the desired directory.
01:38	I will save this file with file name squareit and extension .sci.
01:44	Here we are following the convention of saving functions in .sci format.
01:50	Switch to the Scilab console.
01:53	Now, type Xcos and press Enter.
01:57	Two windows will open,
01:59	a Palette browser and an Untitled Xcos window.
02:04	Now we will make the Xcos diagram.
02:06	This will access the function squareit created just now.
02:10	This can be done by using scifunc block.
02:14	Switch to the Palette browser window.
02:17	Click on the User-Defined function in the pallet browser.
02:21	Locate the block scifunc_block_m in this section.
02:27	Drag and drop it in untitled Xcos window.
02:32	I will zoom the untitled Xcos window for better view.
02:36	I will use the Zoom button as you see.
02:40	Now double click on the scifunc block to configure it.
02:44	A window named Scilab Multiple Values Request will open.
02:49	This window will allow you to change the number of input and output ports of the scifunc block.
02:56	Our function squareit has only one input and output variable.
03:00	Hence, we will keep the settings unchanged.
03:03	Click on OK.
03:05	A new Scilab Input Value Request window will open.
03:09	In the text box, type the function name along with input and output variables.
03:14	This function will be called by the scifunc block.
03:18	In the text box available,
03:20	edit the default function name.
03:22	Type y1 equal to squareit open bracket u1 close the bracket.
03:31	Note that here the input and output variables are u1 and y1 respectively.
03:37	These should be strictly in u and y form and not as per the variable names used in the actual function.
03:45	Cick on OK.
03:47	Another Scilab Input Value Request window will open.
03:51	Keep clicking on OK in the subsequent 3 windows that will appear.
03:56	The scifunc block is now configured.
04:00	Next we will include a sinusoid generator block.
04:04	In the Palette browser window, click on Sources section.
04:08	Drag and drop the Sinusoid generator block in Untitled Xcos window.
04:14	Place the block towards the left of the scifunc block, for convenience.
04:20	Now we need a block to plot the output variable.
04:23	In the Palette browser window, click on the Sinks section.
04:29	Drag and drop the CScope block in the Untitled Xcos window.
04:34	Place the block towards the right of the scifunc block.
04:38	Place it away from scifunc block, for convenience.
04:43	Notice that the CScope block has a red input port.
04:47	This is an event input.
04:49	we need an event generator block.
04:52	In the Palette browser window, click on Sources section.
04:57	Drag and drop the CLOCK underscore c block in the Untitled Xcos window.
05:05	Place it above the CScope block.
05:08	Notice that the CScope block has only one input port.
05:13	But we want to plot both the input and output variables in a single plot window.
05:18	Hence, we need a multiplexer block.
05:22	This block will multiplex two inputs and generate output on one output port.
05:28	In the Palette browser window, click on Signal Routing section.
05:33	Drag and drop the MUX block in the Untitled Xcos window.
05:39	Place the block between the scifunc block and CScope block.
05:43	Let me resize and realign the Mux block.
05:47	Now, let us connect the blocks together.
05:51	Connect the output port of Sinusoid generator block to the input port of scifunc block.
05:57	Now connect the output port of scifunc block to the lower input port of the MUX.
06:04	Connect the output port of MUX block to the input port of CScope block.
06:10	Connect the output port of CLOCK underscore c block to the event input port of CScope block.
06:19	We also have to plot the sine input.
06:22	We have to connect the Sinusoid generator block to the MUX.
06:26	Click on the upper input port of the MUX block.
06:30	Then without releasing, move your mouse pointer towards the link between the Sinusoid generator block and scifunc block.
06:39	To bend the link, release the mouse button or click at places.
06:44	As you bring the pointer on the link, the link turns green.
06:49	Release the mouse button or click once to create a link between these two blocks.
06:55	Now let us see the configuration of other blocks.
06:59	We can change the frequency, magnitude and phase of the sinusoid generator block.
07:04	To do this, double click on the Sinusoid generator block.
07:09	The configuration window will open.
07:11	We will keep the Magnitude and Frequency as 1 and Phase as 0.
07:18	Click on OK to close the configuration window.
07:21	Now let us configure the CScope block.
07:25	Double click on the CScope block to open its configuration window.
07:30	Change the Ymin parameter to minus 2 and Ymax parameter to 2.
07:37	Change the Refresh period value to 10.
07:41	Make a mental note of this value.
07:44	Change the Buffer size value to 2 .
07:47	click on OK.
07:50	Now let us configure the CLOCK_c block.
07:54	Double click on the block to open its configuration window.
07:58	Keep the value of Period as 0.1.
08:02	Change the Initialisation Time to be 0.
08:06	Click on OK.
08:08	Now let us change the Simulation parameters.
08:12	On the menu bar of the Untitled Xcos window click on the Simulation tab.
08:17	Now click on Setup from the drop down menu.
08:22	Change the Final Integration time to match the Refresh period of CScope block.
08:28	The value of Refresh period was 10.
08:32	Hence, put the value of Final integration time as 10.
08:36	Click on OK.
08:38	Now, click on File and then click on Save to save the Xcos diagram.
08:44	Choose a desired directory to save the Xcos diagram.
08:48	However, it is advised to save it in the folder where you have saved the squareit.sci file.
08:56	Click on OK.
08:58	Note that the scifunc block will call the squareit function.
09:02	This means that we should first load the squareit function before we execute the Xcos diagram.
09:09	Switch to the Scilab editor window, which has the squareit.sci file open.
09:16	Click on the Execute button available on the menu bar of the editor.
09:21	This will load the squareit function.
09:24	Now we can execute the Xcos diagram.
09:28	Open the Xcos diagram file.
09:31	Click on the Start button available on the menu bar of Xcos window.
09:37	A graphic window will appear.
09:39	This window will have two plots.
09:42	Input sine wave in black color and output sine wave in green color.
09:47	Notice that the squaring function implemented in the squareit function, has indeed squared the input sine wave.
09:55	Hence, the output sine wave has been shifted to the positive axis.
10:00	Close the plot window.
10:02	Now, let us see how to edit the scifunc block to call a function which has more than one input and output variables.
10:10	Switch to scilab editor window.
10:13	Edit the squareit function to have two input and output variables.
10:19	Edit the output variable as open square bracket y comma z close the square bracket .
10:28	Edit the input variables as open bracket a comma b close bracket.
10:36	We will change the function to shift the squared output by 1 unit.
10:41	Edit the main function line as:
10:44	y is equal to b plus a raise to two put a semicolon in the end.
10:51	Also generate an output whose amplitude will be half of the input.
10:56	Go to next line by pressing Enter key and type:
11:01	z is equal to 0.5 multiplied by a put a semicolon in the end.
11:10	Now save the file.
11:12	Switch to the Xcos window.
11:15	Double click on the scifunc block to configure it.
11:19	In the input port size field, put a semi colon after 1 comma 1 and type 1 comma one again.
11:27	Similarly, in the output port size field, put a semi colon after 1 comma 1 and type 1 comma 1 again.
11:36	Click on OK.
11:38	A new Scilab Input Value Request window will open.
11:41	In the text box,
11:43	put a comma after y1 and type y2,
11:48	put y1 and y2 in square brackets,
11:52	now put a comma after u1 and type u2.
11:57	Click on OK.
11:59	Another Scilab Input Value Request window will open.
12:03	Keep clicking on OK in the subsequent 3 windows that will appear.
12:08	The scifunc block is now configured.
12:11	Let me realign the scifunc block.
12:14	Switch to the Palette browser window.
12:17	In the Sources section, drag and drop the Constant underscore m block in the Xcos window.
12:24	Place it below the Sinusoid generator block.
12:28	Connect the Constant underscore m block to the lower input of the scifunc block.
12:36	The default value of this block is 1.
12:39	Keep it unchanged.
12:41	Double click on the MUX block.
12:44	Change the input port size to 3.
12:47	Click on OK.
12:48	Let me resize the MUX block and I will connect MUX and CSCOPE block properly.
12:59	Connect the lower output port of the scifunc block to the lower input port of MUX block.
13:07	Click on File and choose Save to save the xcos file.
13:12	Switch to the Scilab editor which has the squareit.sci file open.
13:18	Click on the Execute button available on the menu bar of the editor.
13:23	This will load the squareit function.
13:26	Now we can execute the Xcos diagram.
13:30	Click on the Start button available on the menu bar of the Xcos window.
13:35	A graphic window will appear.
13:38	This window will have three plots.
13:40	Input sine wave in black color,
13:43	output sine wave in green color and
13:45	amplitude scaled input in red colour.
13:49	Notice that the function has indeed squared the input sine wave and also shifted it by an offset of 1 unit, which is as expected.
13:59	We also get the amplitude scaled of the input sine wave, as expected.
14:05	Close the plot window.
14:08	Now let us summarize.
14:10	In this tutorial we learnt:
14:12	* To write a squaring function in Scilab
14:15	* To use the scifunc block in Xcos
14:19	* To use MUX block to draw multiple plots
14:22	* To call functions having multiple input and output.
14:26	Watch the video available at the following link.
14:29	It summarizes the Spoken Tutorial project.
14:33	If you do not have good bandwidth, you can download and watch it.
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14:53	Spoken Tutorial Project is a part of Talk to a Teacher project.
14:57	It is supported by the National Mission on Eduction through ICT, MHRD, Government of India.
15:05	More information on this mission is available at spoken-tutorial.org/NMEICT-Intro.
15:15	Thank you for joining. Hope you found this tutorial useful.
15:19	This is Anuradha Amruthkar from IIT Bombay, signing off.

Contributors and Content Editors

Gaurav, PoojaMoolya, Sandhya.np14