unable to get the TTL Signal

[Jatan Pandya]

Hi
I have already done the I/O Test using MediaLab, and it works fine. However, I dont get a TTL signal, when I try to run a MediaLab experiment.:


Essentially, I changed the parameter field of the selfesteem.que file in Sample1, as follows:

For the parameter field of the first row, which is instructions, I have added :
(<255:888:50>)
This is because I am sending a 1 on all datapins of the parallel port. However, nothing happens.

Again, in the parameter field of the second row, I have added the following:
(<0:888:50>) . However, even this goes undetected.

I am using a relay at the other end, to detect the parallel port output.

Pls help me with it because I am stuck up here.

Thanks,
Jatan

[JEC]

Just curious - how are you driving the relay? I ask because parallel ports can't source or sink more than a couple milliamps at best. Higher currents can quickly cause damage.

Have you tested the parallel port's output with an LED + resistor or oscilloscope?

[jarvis24]

But is there any reason to think that if the signal works in the IO test utility that it wouldn't work when using it in MediaLab (assuming the values mentioned are the same, e.g., sending the signal 255 to port 888 for 50ms; and also assuming the same machine is being used for both the test and for the MediaLab session)?