Sync output pulse to UDP data transfer

[karljustin]

I need to transfer data to a system that is set up to align UPD data using 1pps. My issue is that the data will not be consistent in this case and I need to transmit a single pulse as I sent the data via UDP. Naturally latency of the pulse output command vs timing of the UDP data sent is an issue. I am looking for a RT setup, preferably controllable by a laptop, that can accomplish precise pulse output synced with UDP message transmission.   

[TylerK]

Hi,

It sounds like you are trying to do isochronous communication, but I am not quite able to envision what you are describing. To begin with, I have a few big picture questions. Why do you need a trigger synchronized to the transmission of a UDP packet? Or put another way, what are you try to accomplish with the message and triggering scheme? What is the goal of the system?

Regards,
-Tyler

[karljustin]

We are developing a custom simulator for one of our products. A customer is trying to develop an interface to go between their currently incompatible interface and our product. Our product depends on a GPS synced 1PPS to stich several data sources together.

In this stage of their development they are unable to meet our sync requirements. We are helping them develop their data sync capability. In order to do that we need to be able to issue a single, foe 1pps pulse on demand. When we do we need the pulse to arrive very closely to the data we are sending via UDP in order to align the hard coded data time stamps contained in the messages. We have to do it in this manner because we can’t change anything in either of the end systems. 

[TylerK]

Thanks for the clarification. I have some more questions that will hopefully narrow down which hardware platform is best suited for the system you are creating:

• What timing requirements do you have for the 1PPS and UDP packets?
• How accurate and stable does the 1PPS need to be? (I assume you mean pulse-per-second when you use PPS)
• How close does the 1PPS need to be UDP packet?  Are we talking in terms of mili- micro- or nano-seconds?
• When you say close, what point of reference are you using for the UDP packet? The moment the transmit call returns in software? The moment the start of frame delimiter is transmitted over the wire? etc.
• How much data does the system need to handle (throughput)?
• How quick does the system need to handle the data (latency)?
• What types of IO and connective does the system need to have? (e.g. digital inputs/outputs, Ethernet, GPS, ...)

[TheEngineeringBear]

Hey karljustin,

If you are looking to get this issue resolved quickly, the forums may not be the best place.  I'd recommend calling National Instruments and talking with a Sales Engineer who can help you figure out what a system like this would look like and make sure you are able to finish out this project.

1 (800) 531-5066

-Bear