How to have Matlab wait for Arduino to finish execution?

Is it possible to have Matlab wait for code execution on an Arduino before it proceeds without using pause? I am sending data over to an Arduino and then have Arduino do something. Is there any way for me to have Matlab wait for the execution on the Arduino then to continue? I would prefer not to use wait because I have different scenarios where the execution time on the Arduino varies.

Answer 1

[Walter Roberson]

MATLAB has no idea how long it takes Arduino to finish actions. The only way it could know the Arduino is finished is if the Arduino tells it.

There are two basic choices:

1. Have the arduino emit something when the action is finished, and fread() / fgets() / fgetl() the arduino serial port . Reading from a serial port waits until data is ready (or until timeout). If you take this approach you can also configure callbacks to be triggered when data is available from the serial port. This approach would work especially well if you had configured code on the arduino rather than using the convenience layer such as readDigitalPin()
2. After sending the command to the Arduino, request a reading from the Arduino, such as reading a digital pin, knowing that the arduino will not be able to process that until it has finished the previous request. This would work better if you are using the convenience layer rather than sending code to the Arduino yourself.

[Dave]

Hello Walter, thank you for replying. I like option 1. I have in arduino a Serial.print to print a number or character to indicate when execution is over. In matlab do you have an example of how i could implement this? Can i do something like thats similar to while(readline(s) == '10') %wait for stuff end?

[Walter Roberson]

Yes, something like that could work. I was worried about character vector comparison, but I notice that readline() returns a string object instead of a character vector, so using == should be okay.

I was also concerned about whether you mean '10' or char(10) (that is, newline); if you mean newline then readline() will not return that as it removes the terminator.

[Dave]

Thanks again for the reply i will try to implement this tomorrow than i will post back if i have any issues.

[Dave]

Hello Walter, sorry about the delay in response. I hope that you are still able to see the thread. I've set matlab to to return "Done" once an operation is finished, so that Matlab can trigger its next sequence. I saw that matlab has a function called:

writeread

I tried to use this in the form of

writeread(m,"Forward")

But that didnt seem to work.

I then moved on to

while(readline(m) ~= "Done")
    % wait for Arduino to send data.
end

and

while(read(m,4,"string") ~= "Done")
    % wait for Arduino to send data.
end

However, none of these seems to produce the neccessary result. I keep getting a time out issue and then, in my while loops, it reads the data but it stays in the loops for a protracted peroid.

[Walter Roberson]

Unfortunately I have been struggling to install Arduino on my system, so I cannot test this :(

[Dave]

Hi Walter, thank you for replying and assiting with this issue. I currently have the Arduino from the Microsoft Store app installed. I think i got the code to work with a hard pause, vs reading the buffer. I can read the buffer but something is off that i haven't yet figured out. I am still working on it though.