Digital I/O

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Digital pulse trigger I/O to LabView - simplest hardware available?

Hi all,


Not sure if this is in the right subforum, but I thought this is closest to digital I/O since it's mostly hardware related.

I have a piece of equipment in the lab that can send triggers, 5V pulses with adjustable width of 10-1000 ms, and also receive a similar trigger as input. I generally use 100 ms pulses. My challenge is to let my LV software communicate to this machine via these triggers. Simply put: my LV needs a start trigger from the machine, and it should return a trigger when finished.

Of course this was easily built using a USB-6008 or NI-9403 that we have in the lab. Unfortunately, these are not available off-site where this has to work, so I'm looking for a small and cheap piece of hardware to do this task. I figured I could do this with an FTDI TTL232R cable (with the FT232R chip) using bit banging, but that has gotten me quite the headache via LabView (and Python for that matter) by now. I'm sure there must be an easy, cheap way to do this. Interfacing via USB is fine, I also have RS232 and RS485 available if that helps.

Does anyone have a good suggestion for this? Thanks in advance!

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Hi Paul,


The simplest item from NI would probably be either a USB-6000 or a USB-6501. There are probably not the cheapest options on the market, but will be much easier to integrate into your program and this is also worth a lot in my opinion.


On other devices on the market, I cannot really advise, but anything that comes with a driver dll or activeX interface should be relatively straightforward to use in Labview.


Andreas Jost

Applications Engineer

National Instruments


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Thanks for the reply, Andreas.


Using the NI USB interfaces would make life a lot easier indeed, but for various reasons - one being costs - I cannot use these off-site.

The FTDI cable should be suitable for this, and it comes with a DLL (d2xx), and responds as a Virtual COM Port (VCP).


I've dug into this a bit more myself as well. The d2xx allows for full control of each line, but so far this looks rather complicated. Also the LabVIEW "driver" is not well built, and I havent succeeded in directly calling the dll functions.

I also found that it is possible to open the device as VISA and to control at least the CTS and RTS pins. So far I've been able to send an on/off pulse on the RTS pin, by switching the state between Asserted and Unasserted, which is not very elegant. It seems that previously it was even possible to directly control the TX line. This would be preferable, since the RTS is also used when the cable is connected for example.


Any thoughts on this are still appreciated!

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