Speed up serial Communication with parallel computing

Question

Fire Phoenix 2021-3-3

0
链接

此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/761366-speed-up-serial-communication-with-parallel-computing

评论： Fire Phoenix 2021-3-15

Hello everybody,

I have a Mikrocontroller, which (with the help of a gain and phase detector) measure the gain and phase signals of a RLC-Circuit. I want to process and display the signals on the pc with matlab. The problem is that the serial communication is very slow. I want to make it faster by using parallel computing. I want to divide my code in two sections: One section (or one Worker) is reading out the Data and process it and the other is plotting it (Live plotting with drawnow). This all repeats continious in a while-loop. Meanwhile the second worker is plotting, the Data must be read out again. In these case i can make it faster. below is my Code.

The Problem i have is that the second worker only print the first fprintf (The "Resonanzfrequenz"). Their is no plotting. Furthermore i do not feel that the speed is increased. Can somebody help me?

spmd
    switch labindex
        case 1
            %Verbindung zum Mikrocontroller aufbauen
            if ~isempty(instrfind)
                 fclose(instrfind);
                  delete(instrfind);
            end
            %Port vom User angeben lassen, andem der Arduino angeschlossen ist
            s=serial('COM4','BaudRate',9600);   %Einrichten der seriellen Schnittstelle
            
            fopen(s);
            fprintf(s,'%s\n',num2str(freq_start));
            fprintf(s,'%s\n',num2str(freq_stop));
            fprintf(s,'%s\n',num2str(freq_schritt));
            fprintf(s,'%s\n',num2str(messung_start));
            messdaten = zeros(1,(messwerte_max)+1);
            for i=1:(messwerte_max+1)
                messdaten(i) = str2double(fscanf(s));     %Speichern der Messdaten  /Gibt ascii code aus aber betrachtet jeden char einzeln
            end
            fclose(s);
            labSend(messdaten,2);
            
        case 2
            messdaten = labReceive(1);
            amplitude=zeros(1,scala);
            phase=zeros(1,scala);
            temperatur = messdaten(messwerte_max+1);
            inkrement = 1;
            i = 1;
            while inkrement <= messwerte_max   
                 phase(1,i) = messdaten(1,inkrement);
                 inkrement = inkrement + 1;
                 amplitude(1,i) = messdaten(1,inkrement);
                 inkrement = inkrement + 1;
                 i = i + 1;
            end
            f=freq_start:freq_schritt:freq_stop; % Frequenzvektor
            f=double(f);
            amplitude(1:10)=amplitude(10);
            phase(1:10)=phase(10);
            % Umrechnen der Messdaten zu Volt-Werten
            amplitude = amplitude.*(3.3/2^13);
            phase = phase.*(3.3/2^13);
            % Umrechnung der Messdaten in dB für die Amplitude und Grad für Phase
            amplitude=(amplitude-0.9)./0.03;
            phase=-(((0.9-phase)./0.01)+90);
            % -------------------------------------------- Rauschunterdrückung mit Wavelets ----------------------------------------------------
            amplitude_bereinigt=Rauschunterdrueckung(amplitude);
            phase_bereinigt=Rauschunterdrueckung(phase);
            % -----------Berechnung der Frequenz - und Dissipationsänderung-------------
            % Ermittlung der Resonanzfrequenz
            peak_height = 0.8*max(amplitude_bereinigt);
            peak_distance = 10^6;
            [amp_max, fr]=findpeaks(amplitude_bereinigt,f,'MinPeakHeight',peak_height, 'MinPeakDistance',peak_distance);
            % Ermittlung des Dissipationsfaktors
            max_half = amp_max/2;
            % Ermittlung der beiden Frequenzen, die die Halbwertsbreite bilden
            diff = 1;
            f_half1 = 0;
            f_half2 = 0;
            for i=1:length(amplitude_bereinigt)
                kandidat_diff = abs(max_half-amplitude_bereinigt(i));
                if diff > kandidat_diff
                    diff = kandidat_diff;
                    f_half1 = f(i);
                    x1=amplitude_bereinigt(i);
                end
                if amplitude_bereinigt(i) == amp_max
                    break;
                end
            end
            diff = 1;
            for i=i:length(amplitude_bereinigt)
                kandidat_diff = abs(max_half-amplitude_bereinigt(i));
                if diff > kandidat_diff
                    diff = kandidat_diff;
                    f_half2 = f(i);
                    x2=amplitude_bereinigt(i);
                end
            end
            % Halbwertsbreite
            FHWM = abs(f_half2-f_half1);
            % Dissipation
            D = FHWM/fr;
            % ne Umrechnung
            fr = fr/10^6;
             % Ausgabe 
            fprintf('Resonanzfrequenz: %d MHz\n', fr);
            fprintf('Dissipation: %d\n', D);
            fprintf('Temperatur: %d\n',temperatur);
            figure(1);
            subplot(2,1,1);
            plt1 = plot(NaN,NaN,'b'); % Plot empty line
            hold on;
            grid on;
            axis([min(f) max(f) min(amplitude_bereinigt) max(amplitude_bereinigt)]);
            title('Rauschbefreites Amplitudensignal')
            xlabel('Frequenz/[MHz]');
            ylabel('Amplitude/[dB]');
            subplot(2,1,2);
            plt2 = plot(NaN,NaN,'r'); % Plot empty line
            hold on;
            grid on;
            axis([min(f) max(f) min(phase_bereinigt) max(phase_bereinigt)]);
            title('Rauschbefreites Phasensignal')
            xlabel('Frequenz/[MHz]');
            ylabel('Phase/[°]');
            for k = 1:length(amplitude)
                set(plt1,'XData',f(1:k),'YData', amplitude_bereinigt(1:k));
                set(plt2,'XData',f(1:k),'YData', phase_bereinigt(1:k));
                pause(0.01);
                drawnow limitrate
            end
            delete(plt1);
            delete(plt2);
    end  
end

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Answer 1

Walter Roberson 2021-3-3

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链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/761366-speed-up-serial-communication-with-parallel-computing#answer_637976

When you plot inside a parallel worker of any kind, the result cannot be sent to the user display.

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Walter Roberson 2021-3-10

If you are using USB to the arduino instead of true serial port:

Are you emitting a newline after every number? If so then change that to emit a newline less often, even if it is after every pair of numbers would help. USB has a limit on the number of "transactions per second", and newlines can potentially signal the end of a transaction. For USB purposes you would prefer to fill as close to 1020 characters as possible per packet... if you were to group 100 pairs, (4 digits+delimiter)*2*100 -> 1000 characters per packet then your throughput would improve.... at the cost of greater latency, and inability to track the times of the individual readings.

Fire Phoenix 2021-3-15