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Too many output arguments ERROR

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Keir Hunter
Keir Hunter on 24 Jul 2020
Commented: Keir Hunter on 24 Jul 2020
I am making a function to run venting on a pump system. I am getting an error using the matlab timer object. I have the script below and the error let me know if you can help. Thanks!
function vent_man(sec)
v = visa('agilent', 'ASRL1::INSTR');
fopen(v);
hexdata_open = ['02'; '80'; '31'; '32'; '32'; '31'; '31'; '03'; '42'; '33'];
decdata_open = hex2dec(hexdata_open);
hexdata_close = ['02'; '80'; '31'; '32'; '32'; '31'; '30'; '03'; '42'; '33'];
decdata_close = hex2dec(hexdata_close);
t = timer;
t.StartFnc = fwrite(v, decdata_open, 'uint8');
t.StopFnc = fwrite(v, decdata_close, 'uint8');
t.Period = sec;
start(t);
fclose(v);
delete(v);
end
P.S. I have already tried changing the first line to function v = vent_man(sec) which did not work
Error using icinterface/fwrite
Too many output arguments.
Error in vent_man (line 9)
t.StartFnc = fwrite(v, decdata_open, 'uint8');

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Answers (1)

Cam Salzberger
Cam Salzberger on 24 Jul 2020
Edited: Cam Salzberger on 24 Jul 2020
Keir,
The fwrite method for that object doesn't seem to return an output argument. Always try to make sure that you are both using the correct function and using the function correctly.
In this case, it looks like you want to make a function handle for the timer functions, not call the function immediately. So you probably want something more like:
t.StartFnc = @(~,~)fwrite(v, decdata_open, 'uint8');
and similar for the other
-Cam

  3 Comments

Keir Hunter
Keir Hunter on 24 Jul 2020
I am attempting at the start of the timer to write the decdata_open to the pump and then when the timer stops to write the decdata_close to the pump. When I run your solution I get another error:
Error using timer/subsasgn (line 137)
The name 'StartFnc' is not an accessible property for an instance of class 'timer objects'.
Error in vent_man (line 9)
t.StartFnc = @(~,~)fwrite(v, decdata_open, 'uint8');
Cam Salzberger
Cam Salzberger on 24 Jul 2020
Ah, I copied from your code without looking. The parameter name is 'StartFcn' not 'StartFnc'.
Always read the error messages - they're usually pretty useful.

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