MATLAB/Arduino fprintf not working

I am writing a program in Arduino that waits for MATLAB to ask it to send data. Once asked, it sends sensor data, until MATLAB asks it to stop. When I use Arduino's built-in serial emulator, it works fine. When I use my MATLAB script, it breaks down.

I've managed to troubleshoot my code by having Arduino light up different LED at different points in the code, so I know that I got to that line. In Arduino, the section of interest looks like this:

void loop()

{
  int x=0; //Initialize serial communication marker
digitalWrite(13, HIGH); //Check if I got to this line before hang
if (Serial.available()>0) //Check if there is serial data available
{
      digitalWrite(4, HIGH); //Check if I got to this line before hang
      delay(1000); //pause long enough (1 s) so I can see the light
  x=Serial.read(); //read data

and then the rest of the code operates. So, the LED attached to pin 13 lights up, meaning its entering the loop, but the LED on pin 4 never lights up, meaning it never receives serial data. Now for the MATLAB side, here's how I'm trying to send a start command:

fclose(instrfindall); %close all serial comms
s=serial('COM4','BaudRate',9600); %start serial port to arduino
fopen(s); %open port
try
    start='/A01'; %start command
    fprintf(s,start) %print start command to arduino
    tline = fgetl(s); %read data from arduino, which waited until start command
    count = 0; %initialize count
    while ischar(tline) && count<1000
        disp(tline) %display arduino data
        tline=fgetl(s); %get next line of data
        count=count+1;
    end
    fprintf('%s','.A01'); %stop command
    fclose(instrfindall); %close all serial comms
catch
    fclose(instrfindall);
end

The code breaks down at tline=fgetl(s) with the warning:

Warning: A timeout occurred before the Terminator was reached.

I'm pretty sure whats happening is fprintf(s,start) isn't working for some reason. That means Arduino never sends data back, meaning fgetl(s) will never read anything, causing the code to hang. When I modify my code slightly to use a text file instead of a serial object it works fine. Has anybody had this problem? I've put a lot of effort into trying to solve it on my own and ran out of ideas, so any help solving this would be greatly appreciated.

Answer 1

[Adam]

Thought I'd led other people know how I fixed this. When I told MATLAB to start the serial connection, there was a delay before the Arduino started up and was able to receive data. That delay took longer than I had pauses in for. I put a 3 second pause before I wrote the start command and everything worked great. Thanks again Walter for trying to help with this.

Answer 2

[Walter Roberson]

Dang system ate my answer. Excuse me for being concise.

fprintf(s,'/A01') is defined as fprintf(s,'%s\n','/A01') which transmits your defined terminator after your string. You might not have matched terminators with the other side.

Later you have fprintf('%s','.A01') which is

[Adam]

Thank you for the help. I hadn't thought about that, and I'm not exactly sure how to fix it. I figure it might help if I let you know what my start and stop commands are, start is "/" , and stop is ".". If you have any ideas/pointers/help files that might point me to the right direction I'd appreciate it.

Here's something interesting, that LED that should light up if there is data in the serial buffer, does light up if I transmit the stop command:

fprintf(s,'%s','.A01');

but it doesn't if I transmit the start command:

fprintf(s,'%s','/A01');

Do you think it would be prudent to simply change my start command to something without neither a / nor a \?

Again, thanks for taking the time out of your day to help me, I appreciate it.

[Walter Roberson]

I've been having problems posting to this page.

What I started to say about fprintf('%s','.A01') is that you are missing the s to tell it to print to the serial port, fprintf(s,'%s','.A01')

Perhaps this contribution would help: http://www.mathworks.com/matlabcentral/fileexchange/27843-arduino-io-package-slides-and-examples

It took me a bit of checking around to find, but I see that the standard Arduino library sends carriage return and new line (ASCII 13 and 10) for println(), and I see that both Serial.available() and Serial.read() only pay attention at the byte level, and do NOT wait until a terminator has been received.

Ummm -- do you have a Serial.begin(9600) in your Arduino setup() routine ?

[Adam]

I fixed the problem with fprintf(s,'%s','.A01'), thanks for catching that. I have seen that set of files but it wasn't exactly what I wanted (you can't include libraries as far as I can tell). I do have Serial.begin(9600) in Arduino.

I've discovered that I don't think the original problem was really with fprintf. When I step through my matlab script, everything works perfectly. When I try to run it full speed, it hangs at tline=fgetl(s) and gives me:

Warning: A timeout occurred before the Terminator was reached.

Can you think of a reason the script would work fine stepping through but not when ran full speed? I'm thinking it has something to do with delays in sending data but I'm very new to comms stuff. These comms problems are a lot harder to trouble shoot than normal scripts for me. Again, thanks for your help, I appreciate it.

[Walter Roberson]

You could _try_ pause(1) after the fprintf(); you could also try a brief pause after sending each character, such as

fwrite(s,'/'); pause(0.02); fwrite(s,'A'); pause(0.02)

and so on.

I wonder, though, what the default properties of the serial port are? I wonder if it is defaulting to a buffered mode? I don't think I have a serial port handy to check that out on.

[Adam]

I had tried pauses already, unfortunately they didn't help. The default properties on the serial port are:

Bps:9600

Data bits:8

Parity:None

Stop bits:1

Flow Control:None

Use FIFO Buffer

Receive Buffer:14

Transmit Buffer:16

Answer 3

[adel moussidene]

a have a probleme with a port when a simulink a cant use a interface graphique you have a solution a wanna controle my onduleur inyone can help me plz