Change Output State if Connection is Lost

[JimmyCrawford]

Hello,

I am using a USB-6341 XSeries multifunction DAQ system to control an experiment involving a heated pipe.  I am using MATLAB to read a number of analog sensors, and the Digital Outputs to activate relays to control some heaters and a pressure relief valve.  My problem is that if I lose power, someone kicks a cable, or my computer crashes mid-test, I want the relays to turn off (ie return all the digital outputs to 0), for safety reasons.

I have figured out how to have the default output on power up be 0, but I havent come across anything describing how to do the same thing if a connection with the computer is lost.  Is there a property inside the DAQ that I can program to do something like this?

Thanks

Jimmy

[Tirmizi]

you need to send some ack commands set by your self like PC send ack code and from DAQ you sent a counter value to PC, every time ack recieved , increment the counter and sent it PC. the ack and counter exchange interval should be set after every 1 sec or even less its upto you. make a check timer in your DAQ which check whether ack recived or not . if it is not recived for 1 sec means PC lost comm so THE check timer set you DAQ Digital IOs to boolean 0.

[John_P1 · Accepted solution]

The 6341 has a built-in watchdog timer for the digital I/O lines which is mentioned in the X Series User Manual in chapter 6 (pdf link).

You reset the watchdog timer from your software loop--if the timer expires the hardware goes into a pre-defined state.

I have no idea how it is configured in MATLAB, but in the C API the functions used are DAQmxCreateWatchdogTimerTask to create the task and DAQmxControlWatchdogTask to reset the timer.

Best Regards,