How to plot realtime ECG graph using arduino uno MATLAB

Sorry for broken English

I'm working on a project that need to displaying a realtime ECG graph by using MATLAB and arduino uno. This is my arduino code.

void setup() {
  Serial.begin(57600);
}
void loop() {
  float voltage = analogRead(A0)*(5.0/1023.0);
  Serial.println(voltage);
}

and this is my code in MATLAB

close all
clear all
delete(instrfind(('Port'),('COM5')));
s = serial('COM5','baudrate',57600,'Databits',8);
fopen(s);
ylim([-2,5]);
x = 1:100000;
h = animatedline('MaximumNumPoint',500);
grid on
grid minor
while(1)
    for i = 1:100000
        voltage = fscanf(s);
        y(i)=str2double(voltage);
        addpoints(h,x(i),y(i));
        drawnow;
    end
    clearpoints(h)
end

for some reason, an ECG graph didn't show up on a moving graph.

EDIT : an ECG graph is showing up right now, but this ECG graph's width on x-axis is too large.

Answer 1

[Walter Roberson]

That code looks pretty good.

What I would check first is the values stored into y(i) . They might somehow be outside the range -2 to 5. For example somehow the voltage might not look like a number so str2double() might be creating nan.

[Walter Roberson]

After your code changes, you are no longer setting an xlim . As you add more data, xlim is automatically going to get larger, and the plot is going to scale down the output instead of panning.

When you loop back after the clearpoints(), the xlim is not going to get any smaller, so it would stay at the 100000