Thread Subject: Parallel port getvalue

Hello all,

coming back again with something wrong (?) with my parallel port. There is a device with buttons, so the volts in that electric circuit are supposed to change when someone presses a button. We have checked that the buttons are working with a voltmeter.

However, when I generate a simple (but perhaps built not in the right way) code the only value I read from the parallel port is '1'. This value is present either the device with the buttons is plugged in or not, and either I press a button or not. No change at all.

The device is connected to LPT1, which works fine as I see in the Device Manager. I try to read data from Port 0, pins 2 to 4.

I register the digital object and execute a code as:

dio = digitalio('parallel', 'LPT1');
inlines = addline(dio, 0:4, 'in')

for i = 1:1000 %Get the value 1000 times
start(dio)
value_1(i) = getvalue(dio.Line(1));
value_2(i) = getvalue(dio.Line(2));
value_3(i) = getvalue(dio.Line(3));
value_4(i) = getvalue(dio.Line(4));
pause(2)
stop(dio)
end

delete(dio)

BUT the value I get it always 1, no matter the condition, no matter pressing the buttons, no matter if the device is plugged in or not...

Any ideas?

Hi Jimmy,

We are having exaclty the same problem as you. Could you finally solve it?

We'll really apreciate your help :)

"Jimmy " <dvoudour@phed.auth.gr> wrote in message <hkrh5g$agv$1@fred.mathworks.com>...
> Hello all,
>
> coming back again with something wrong (?) with my parallel port. There is a device with buttons, so the volts in that electric circuit are supposed to change when someone presses a button. We have checked that the buttons are working with a voltmeter.
>
> However, when I generate a simple (but perhaps built not in the right way) code the only value I read from the parallel port is '1'. This value is present either the device with the buttons is plugged in or not, and either I press a button or not. No change at all.
>
> The device is connected to LPT1, which works fine as I see in the Device Manager. I try to read data from Port 0, pins 2 to 4.
>
> I register the digital object and execute a code as:
>
> dio = digitalio('parallel', 'LPT1');
> inlines = addline(dio, 0:4, 'in')
>
> for i = 1:1000 %Get the value 1000 times
> start(dio)
> value_1(i) = getvalue(dio.Line(1));
> value_2(i) = getvalue(dio.Line(2));
> value_3(i) = getvalue(dio.Line(3));
> value_4(i) = getvalue(dio.Line(4));
> pause(2)
> stop(dio)
> end
>
> delete(dio)
>
> BUT the value I get it always 1, no matter the condition, no matter pressing the buttons, no matter if the device is plugged in or not...
>
> Any ideas?