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This example shows what type of vector would be aquired if the DSP was constantly counting up and outputting these numbers. We are taking in vector of size 6 at some random point in the operation of the DSP: %In the MATLAB terminal: y = GetSerialData('com2', 38400, 6)y =7 8 9 10 11 12 The numbers are counting up as written in the C DSP code. We can also specify signed numbers and if we catch the counting at the right moment we get an output like this: y = getSerialData('com2', 38400, 6, 1) y =125 126 127 0 -1 -2

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Other notes

Other functionality can be added to this code. This may include other serial port issues (such as handshaking or parity) or even the formatting of the data coming out of the dsp.For instance, to get numbers larger than bytes in each vector index, you can modify how data is written to the MATLAB vector when it is acquired in the Receive function (in the code).Code for modifying serial port abilities is commented in the main() function where the serial port handle is initialized.

Using matlab gui features

MATLAB has some nice Graphical User Interface (GUI) features which can be used to control the flow of data to and from the serial port. The basic implementation consits of a blank window (figure) which can have differentinterface elemnts palced on it. These elements can be sliders, buttons, text boxes, etc...

When an element is accessed (for instance, a slider is moved, or a button is pushed), MATLAB will execute a "callback routine" which is a MATLAB function defined by the user. Desgining these interfacesis simple.

Creating a user interface with sliders

1 % ser_set: Initialize serial port and create three sliders 23 % Set serial port mode 4 !mode com2:38400,n,8,15 6 % open a blank figure for the slider7 Fig = figure(1); 89 % open sliders 1011 % first slider 12 sld1 = uicontrol(Fig,'units','normal','pos',[.2,.7,.5,.05],... 13 'style','slider','value',4,'max',254,'min',0,'callback','wrt_slid');14 15 % second slider16 sld2 = uicontrol(Fig,'units','normal','pos',[.2,.5,.5,.05],...17 'style','slider','value',4,'max',254,'min',0,'callback','wrt_slid'); 1819 % third slider 20 sld3 = uicontrol(Fig,'units',normal','pos',[.2,.3,.5,.05],... 21 'style','slider','value',4,'max',254,'min',0,'callback','wrt_slid');
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Lines 12 through the end create the three sliders for the user interface. Several parameters are used to specify the behavior of each slider. The first parameter,Fig, tells the slider to create itself in the window we created in Line 7. The rest of the parameters are property/value pairs:

  • units : Normal tells Matlab to use positioning relative to the window boundaries.
  • pos : Tells Matlab where to place the control.
  • style : Tells Matlab what type of control to place. slider creates a slider control.
  • value : Tells Matlab the default value for the control.
  • max : Tells Matlab the maximum value for the control.
  • min : Tells Matlab the maximum value for the control.
  • callback : Tells Matlab what script to call when the control is manipulated. wrt_slid is a Matlab file that writes the values of the controls to the serial port.
Every time a slider is moved, the wrt_slid.m file is called:

1 % wrt_slid: write values of sliders out to com port 23 % open com port for data transfer 4 fid = fopen('com2:','w');5 6 % send data from each slider7 v = round(get(sld1,'value')); 8 fwrite(fid,v,'int8');9 10 v = round(get(sld2,'value'));11 fwrite(fid,v,'int8'); 1213 v = round(get(sld3,'value')); 14 fwrite(fid,v,'int8');15 16 % send reset pulse17 fwrite(fid,255,'int8'); 1819 % close com port connection 20 fclose(fid);
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Line 7 retrieves the value from the slider using the get function to retrieve the value property. The value is then rounded off to create an integer, and the integeris sent as an 8-bit quantity to the DSP in Line 8. (The number that is sent at this step will appear when the serial port is read with READSER or a C equivalent in your code.) The othertwo sliders are sent in the same way. Line 17 sends 0xFF (255) to the DSP, which can be used to indicate that the three previously-transmitted values represent a complete set of data points.This can be used to prevent the DSP and Matlab from losing synchronization if a transmitted character is not received by the DSP.

Line 20 closes the serial port. Matlab buffers the data being transmitted, and data is often not sent until the serial port is closed. Make sure you closethe port after sending a data block to the DSP.

Advanced features

The slider example shows some basic features of the gui tools. The file descriptor is generated into the workspace so that it can be used for writing. But other elements, such as text boxescannot be dealt with as easily. The Parameters from these can be accessed through their returned handles. Some examples:

%GUI.m %****Sample GUI, Text and a Button***%open a blank figure Fig = figure(1);set(Fig,'Name','Test GUI'); %Space to enter texted2 = uicontrol(Fig,'backgroundcolor','white','units','Normalized','pos',[.1,.6,.4,.05],...'string','Default Text','style','edit'); %Buttonbut1 = uicontrol(Fig,'foregroundcolor','blue','units','Normalized','pos',[.1,.4,.5,.1],...'string','Press Me!','style','pushbutton','callback','SampleGUI');

A Text box is created with default text in it that says: "Defaul Text". A button is also created, which when pressed, will execute the callback function SampleGUI.m

%SampleGUI.m %Get TexttestText = get(ed2,'string')

Now testText holds whatever string was enetered into the text box. The function get() is used to retrieve the data from the 'string; parameter in the ed2 handle. MATLAB help uicontrol gives the full list of options for interface elements.

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Questions & Answers

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Preparation and Applications of Nanomaterial for Drug Delivery
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Source:  OpenStax, Digital signal processing laboratory (ece 420). OpenStax CNX. Sep 27, 2006 Download for free at http://cnx.org/content/col10236/1.14
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