How can I save serial monirtor values from arduino to multiple vectors?

Hi !

I have a project that uses Arduino Uno and Matlab to calculate Pulse Transit Time (PTT) between 2 sensors. I am trying to work things out with one sensor first. The idea is to use split function to save the data into two vectors, one for the time and the other for the voltage. but I keep getting this error:

"Error using strsplit (line 80)

First input must be either a character vector or a string scalar."

Also, I want to store the time value as 'long' type in the vector since I need the maximum accuracy for this project. Is there a way to do so? In my code I used str2double and it doesn't work.

My Arduino code:

int SwitchState=0;
int prevSwitchState=0;
long time;
void setup() {

Serial.begin(9600);
//pinMode(2,INPUT);

}

void loop() {

   SwitchState = digitalRead(2);
   if (SwitchState == HIGH  ){
  time = micros();
  int sensorval = analogRead(A0);
  Serial.print(sensorval);
  Serial.print("\t"); 
  Serial.print(time);
  Serial.println();
  }}

And this is my Matlab code:

clear all;
clc;
delete(instrfindall);
a = serial('COM3','BaudRate',9600);

fopen(a);
  for i=1:1000 %while if constant acquisition is needed. 
            sSerialData = fscanf(a,'%d');
            flushinput(a);
            t = strsplit(sSerialData,'\t'); 
            y(i) = str2double(t(1)); 
            time(i) = str2double(t(2));
    end    
fclose(a);
plot(time,y);

[Madhu Govindarajan]

Is there a reason you are not using MATLAB support package for Arduino? Because this allows you to directly to collect data from Analog sensors and plot as is. The caveat would be that you cannot do it at the same speed (micro seconds). This could possibly be addressed by Simulink support package. Just giving you other options.

Either way, to continue going down the same path here is a suggestion. First read the sSerialData from MATLAB Command Window and see what the datatype is. The error message says that it has to be char or string for strsplit. If it is not one of those datatypes consider converting it to one of those before using the strsplit.

If you can post an example string that you receive along with the datatype, then others can chime in and help you move forward as well.

[Maysamf]

Thank you for your comment.

I have resolved this issue as you said by changing the data type.

To answer your question on why I am not using the package, I want to store the data in two arrays not only plot it. I want to process the data using some mathematical equations then send it back to the arduino as one value.

Thank you again.

[Madhu Govindarajan]

Gotcha, I am glad your issue is resolved :)