As the error message suggests, the serial connection is being timed out when reading from serial using fgets. I suspect this is due to the absence of a terminating character in the string transmitted by arduino.
A read operation using fgets in MATLAB completes/returns only when the terminator character is read.When there is no terminator character in the data being read by fgets, it causes a timeout. The default terminator character for serial object in MATLAB is 'LF' (line feed or new line).
1. In your arduino code, just append the new line character to your string before sending it over serial :
String send_string = "I" + string_R2 + "\n"; % Append the new line/LF character
In your MATLAB code, just to be sure, you could set the Terminator value for the serial object to LF :
%INITIALIZE THE SERIAL PORT
s = serial('com3');
set(s, 'BaudRate', 9600); % set BaudRate to 9600
set(s, 'Parity', 'none'); % set Parity Bit to None
set(s, 'DataBits', 8); % set DataBits to 8
set(s, 'StopBit', 1); % set StopBit to 1
% set terminating character to LF/new line
set(s,'Terminator','LF')
Also in the MATLAB code, instead of waiting for 10 seconds using pause, you could just wait till serial data is available(by querying the BytesAvailable parameter, and then read the data :
%Wait few secs for the Arduino to do things
%pause(10);
while(get(s,'BytesAvailable')==0)
% wait for arduino to send data
end
%receive string from serial
%MATLAB receives the string "I1000"
stringI = fgets(s);
2. Alternatively, if you don't want to modify your arduino code, you could just modify the MATLAB code to use fread to read only the number of bytes of available data without it waiting for the terminating character.
%Wait few secs for the Arduino to do things
%pause(10);
while(get(s,'BytesAvailable')==0)
% wait for arduino to send data
end
%receive string from serial
%MATLAB receives the string "I1000"
%stringI = fgets(s);
stringI = fread(s,get(s,'BytesAvailable'), 'uint8');
