TTL signal to Biopac

Greetings to all

If you encounter problems in sending a TTL signal to a physiology recording equipment (in my case a Biopac) it may be due to your PCs settings. In my case, my computer, port, TTL cable and Biopac connections were working (although it took days to check all components individually). But the TTL would simply not get through to the physio recording.

Try the following solution: In your computer settings-->device manager--> LTP1 switch parameters to "manual". Then, every time you start up the computer, run the IOexe utility (provided with MediaLab) and try a couple of different addresses - I do 888, then 889, then 890, send signal every time, and after a couple of tries the port somehow "wakes up". I'm not a programmer, but this saved my sanity! This trick won't work when the LPT1 settings are switched to "auto". The technicans have no idea why.

A trick to check whether your whole connectivity circuitry from A to Z works, is to connect your cable and start recording on the digital channel of interest, while booting the MediaLab PC. At some point, the computer will try all its hardware, including its ports. At that moment, it sends a 100ms 5V pulse to each pin in the parallel port as well, which should be recordable if your circuitry is ok. If not, check for loose connections etc.

...and...be patient...VERY patient...you will finally get there.

XeniasD