Sample a signal from an Arduino using the Serial port

Hi!

Got an issue. So I'm using an Arduino Uno but I'm not able to get sample a signal well. Need some help or advices with this.

This is the code I'm using to sample the signal.

clear all
clc

arduino=serial('/dev/tty.usbmodemfd131','BaudRate',9600,'InputBuffer',512);

fopen(arduino);

k = 0;
c = 0;

x=linspace(1,2,1000);

for i=1:length(x)
  y(i)=fscanf(arduino,'%d');
end

fclose(arduino);
disp('making plot..')
plot(x,y);
grid on;

for i=1:length(x)
  if(y(i) > 0.5)
        k = k +1;
    end 
end

k/length(y) %duty cycle

From the arduino I'm sending a square wave at approx 500 Hz. I'm getting like 20 samples per period, but I need to be able to sample other signals than 500 Hz ones as well.

How can I make it faster somehow? Any suggestions are welcomed :)

Answer 1

[Walter Roberson]

500 samples per second, N characters per sample, 1 space (or end of line) character per sample to allow the samples to be distinguished from each other. This is 500 * (N+1) characters per second. 10 bits are needed to send each character over the serial port, so that is 10 * 500 * (N+1) = 5000 * (N+1) bits per second. This must fit in to the 9600 bits per second that you have set the serial port to, so we get

5000 * (N+1) <= 9600

and we see from that that you can only sustain the rate if N, the average number of characters per sample, is strictly less than 2 (e.g., 1).