CDAQ 9188 - Samples Avaiable to read Question

[Estie]

Hello Everybody,

I am currently having some questions about the cDAQ 9188. Following Moduls are plugged: NI 9222 and NI 9223, and it is connected via Gbit Ethernet. Currently doing some tests about latency and jitter of the data under some circumstances. So i programed a little VI to test wether there are samples in the buffer avaible to read or not and how fast they have to be readed so there is no buffer overflow.

Following question occured during the programming:

1. If the daq_read.vi trys to read the buffer and there are not enough samples to read, it seems like the buffer become unreadable for a certain time. Is this time specified some where?

2. It seems like new samples are only avaible periodical. In the screenshot the problem is shown. Every 0,1s new samples are avaiable, so the samples have a latency at least of 0,1seconds. Is there a way to lower this time? Or set this time?

Greetings and thanks

Estie

[Tom_W_[DE]]

Hey Estie-

The periodically available samples are most likely due to the functioning of Nagle's algorithm by the chassis.  Brian has a good, short writeup here.

Can you explain the issue you are seeing in 1) a bit more?  Or maybe post some code that replicates the issue?

Thanks-