Using RIO to trigger PXI-2503 switch

[JTT844]

Hi,

I need to be able to close a switch on a PXI-2503 MUX within a specified time (10 ms) of an input signal to a PXI-7833R RIO card going low. Both cards are in the same

PXI chassis. I realize the best way to do this would have been to have both signal lines attached to the RIO but the hardware guys didn't give me this option and it's too late to go back and change it.

I see there are PXI Trig lines in the RIO I/O connector list. I'm curious if it's possible to have the RIO send a trigger signal on one of these PXI trigger lines when the appropriate input goes low and have the 2503 wait for that trigger to close the appropriate switch.  Is this possible? Reliable? If so, what details/issues do I need to address?

Thanks!

John

[Captain_Kirby]

Hi John,

You definitely can use the PXI trigger lines to trigger another card in your PXI chassis from your FPGA card. There are a number of trigger lines that are available to you, and all of them should meet your timing requirements. Choosing which trigger line to use will depend on the physical configureation of your chassis. You can find all the information on connecting to these lines and operating them in your FPGA card manual:

R Series Intelligent DAQ User Manual, Page 2-20, Section "RTSI Trigger Bus".

You can use Digital IO methods in the FPGA code to read or write to these lines.

One thing to note about your specific switching card (the PXI-2503). The device requres the start trigger to be a pulse of at least 70ns. So be sure that you produce an appropriate pulse width.

[JTT844]

Great, Thanks!

How do I set up the PXI-2503 to wait for the RIO's trigger? Is there any example code you could forward along??

Thanks!

John

[Captain_Kirby]

Hi John,

There are some great examples in the NI Example Finder. Search for Switch and DMM, and you will find a number of good examples. In particular, you may take a look at "Switch scanning with DMM - Handshaking.vi". This VI demonstrates how to trigger a scan based upon a trigger from the DMM. It should be fairly simple to modify this example to work without the DMM or the handshaking.

[JTT844]

I notice the trigger naming convention is a little different on the Switch vi (NI-Switch Configure scan trigger) and the RIO IO trig out options.

After reading the help sections of each of the VI's, it seems to me I may be able to send a pulse out from the RIO's Connector0-> Trig0 line and have the switch read from the TTL0 trig input.  Is the RIO's Trig0 the same as the 2503's TTL0?  Will this work or am I missing something?

Thanks, Cap'n!

John

[Captain_Kirby]

Hi John,

The naming convention should be pretty similar. In particular, for the RIO, don't look under any of the connectors, just look under the PXI listing in the I/O resource window. Here you can find triggers like TRIG0, STAR or LBR0. You can then connect to these same trigger sources when programming the switch. The naming convention should be very similar. Here is a screenshot of the FPGA I/O screen showing a portion of the triggers available from the PXI.





Message Edited by Captain Kirby on 07-16-2008 12:06 PM

[JTT844]

Here's the input trigger list from the niSwitch Configure scan trigger vi. The closest match I see to the RIO's Trig0 is TTL0. Do those match??

thanks!

jt

[Captain_Kirby]

Hi John,

Sorry for the misunderstanding in the last post (a picture really is worth a thousand words.) Your exactly right. The TTL triggers you see in the Switch configuration are equivalent to the TRIG lines in the FPGA I/O list (so TTL0 is TRIG0 and so on and so forth.) So if you output your pulse on TRIG0, and move your scan with TTL0, you should have no problem. Just be carefull that only the FPGA is driving the line when you operate it (make sure no other cards are using that trigger line for somthing else.)

[JTT844]

Great. Thank you for the clarification!

[JTT844]

Hi Kirby,

I've set up my RIO code to send a 1 us pulse on TRIG6 when one of the FPGA I/O's goes from low to high and I've set the PXI-2503 to look at trigger input TTL6 but it doesn't seem to be working. I'm running the RIO in emulation mode. Will the RIO send an actual trigger in emulation mode?? If so, do you have any suggestions as to how I can get the 2503 to trigger on the RIO's trigger pulse?

Thanks!

John