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The script file

In the script we have to perform the following tasks:

  • When the GUI is launched the DSK should be loaded with a default model (SQRT)
  • When the user selects a new model>Its correspondent *.out file should be loaded to the DSP.
  • When the modulation index is changed, its new value should be written to the DSP through the correspondent RTDX channel.
  • When the carrier frequency modulation index is changed, its new value should be written to the DSP through the correspondent RTDX channel.

The following steps describe this implementation.

  • The initialization routine “AM_OpeningFcn”:
function AM_OpeningFcn(hObject, eventdata, handles, varargin) last_model=1;handles.last_model=last_model; modelName = gcs;%connect to the board CCS_Obj = connectToCCS(modelName);% Identify RTDX channel names/modes chan_struct(1).name = 'InputModulation';chan_struct(1).mode = 'w'; chan_struct(2).name = 'freq';chan_struct(2).mode = 'w'; handles.rtdx_chan1=chan_struct(1);handles.rtdx_chan2=chan_struct(2); % Identify RTDX host buffer parametersRTDX_config_struct.Buffsize= 32768; RTDX_config_struct.Nbuffers = 4;RTDX_config_struct.Mode = 'continuous'; %building the full path of the file to be loadedCodegenDir = fullfile(pwd, ['AM_Coherent' '_c6000_rtw']);OutFile = fullfile(CodegenDir, ['AM_Coherent' '.out']);%Load is needed for rtdx setup CCS_Obj.load(OutFile,20);% Set up RTDX r = setupRTDX(CCS_Obj, chan_struct, RTDX_config_struct);handles.pipe=r; handles.CCS_Obj=CCS_Obj;%last_x and last_y are the initial values of %the Index and the carrier respectivelylast_x=1; last_y=15000;handles.last_x=last_x; handles.last_y=last_y;handles.output = hObject; % Enable all RTDX channelsr.enable('all'); % Update handles structureguidata(hObject, handles); %use the change-model function in order to load the current model.%this function loads a model to the DSK after initiallization (= the code %above)ChangeModel(handles.last_model,handles.CCS_Obj,handles.pipe,handles.last_x,handles.last_y); )
  • When you select a new model, the following code is invoked:
function listbox1_Callback(hObject, eventdata, handles) handles.last_model=get(hObject,'Value') ;ChangeModel(handles.last_model,handles.CCS_Obj,handles.pipe,handles.last_x,handles.last_y);

An external function (written in the ChangeModel.m file) will be used to select the model:

%1. halts the current model %2. free the rtdx channel%3. redefine the rtdx channel %4. loads the current model%5. binds the rtdx to the current model %6. run the CCS and enable the rtdx.%7.writes the last given index modulation to the rtdx %parameters:%m - flag that tells if the model is coherential or sqrt %CCS_Obj - the target%r_old - the old rtdx channel %last_x - to keep the current Index%last_y - to keep the current carrier frequency function r=ChangeModel(m,CCS_Obj,r_old,last_x,last_y)%halt the current model CCS_Obj.halt;%free the curent rtdx channel cleanupRTDX(CCS_Obj,r_old);%redefine the rtdx: chan_struct(1).name = 'InputModulation';chan_struct(1).mode = 'w'; chan_struct(2).name = 'freq';chan_struct(2).mode = 'w'; handles.rtdx_chan1=chan_struct(1);handles.rtdx_chan2=chan_struct(2); % Identify RTDX host buffer parametersRTDX_config_struct.Buffsize= 32768; RTDX_config_struct.Nbuffers = 4;RTDX_config_struct.Mode = 'continuous';%reload the new model switch mcase 1 model='AM_Coherent';case 2 model='AM_Sqrt';end CodegenDir = fullfile(pwd, [model '_c6000_rtw']); OutFile = fullfile(CodegenDir, [model '.out']); CCS_Obj.load(OutFile,20);% set up the new rtdx channel and run the target r = setupRTDX(CCS_Obj, chan_struct, RTDX_config_struct);CCS_Obj.run; r.enable('all');% keep the last Index and carrier frequency: if last_x~=1r.writemsg(chan_struct(2).name,1/last_x); end
  • Changing the modulation index:
function slider1_Callback(hObject, eventdata, handles) last_x=handles.last_x;r=handles.pipe; x=single(get(hObject,'Value'));if or (y<last_y,y>last_y) %if the Index was changed: r.writemsg(handles.rtdx_chan1.name,1/x);%the Index increases when the added amplitude decreases %and thats the reason that we write 1/x to the rtdxhandles.last_x=x; endguidata(hObject, handles);
  • Changing the carrier frequency:
function slider2_Callback(hObject, eventdata, handles) last_y=handles.last_y;r=handles.pipe; y=single(get(hObject,'Value'));if or (y<last_y,y>last_y) r.writemsg(handles.rtdx_chan2.name,y);handles.last_y=y; endguidata(hObject, handles);
AM Model Graphic User Interface

You may change the modulation index and frequency for both models, and observe its influence on the modulated and demodulated signals.

Appendix

A configurable carrier wave generator

The Simulink sine wave block cannot be configured during run-time; its frequency is a parameter that should be set in advance. We will introduce the implementation of a block where the frequency is a variable that can be set in real-time (In this case using RTDX). The block is based on the following relationship:

cos ω c t = Re e c t size 12{"cos"ω rSub { size 8{c} } t="Re" left [e rSup { size 8{jω rSub { size 6{c} } t} } right ]} {}

In the discrete case the following relationship applies:

cos ω c nT s = cos f c f s n = Re e j2π f c f s n size 12{"cos"ω rSub { size 8{c} } ital "nT" rSub { size 8{s} } ="cos"2π { {f rSub { size 8{c} } } over {f rSub { size 8{s} } } } n="Re" left [e rSup { size 8{j2π { {f rSub { size 6{c} } } over {f rSub { size 6{s} } } } n} } right ]} {}

{} The following model implements the last equation. Please note that a feedback path was included for phase continuity

Carrier Wave Generator

The coherent detector (in brief)

The coherent detector principle of operation is in Figure 39. The AM example model ( AM_Coherent.mdl ) is shown in Figure 40.

Coherent SQRT Demodulation Principle of Operation
Amplitude Modulation Example with Coherent Detection

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