I needed to implement an existing communcation protocol on a
RT-PXI-System. This communiction just needs a small platform
abstraction layer (PAL) which allows simple commands as
read/write/open/close communication channel. I decided to write the PAL
in CVI and not in Labview, because this would be more complicated to
use with the c-program of the communication protocol. I had to use TCP
communication, which is really inconvenient for a fast RT-like
communication. However i managed to get it to work with
ServerTCPRead/Write etc. I call dll-functions of my
communication-protocol from Labview, because i need some of the Labview
features, as accessing the FPGA cards. It runs, but the performace is
really quite bad. It works considerable better by switching to half
duplex, which i understand could only be the case if the implementation
of the TCP-Stack is somehow strange. With half duplex mode i barely
manage to get the desired performance, but i have to use quite big
buffer to get a continuous data stream. I am not very comfortable with
this and i think this should work better.
So my questions are:
1) Is it really still true, that there is no UDP-API for Labwindows/CVI
running on a RT-PXI-Target? Or have i just missed something? I find it
quite unbelievable that this really basic feature is not implemented. I
do not need any fancy Server/Client-Thread implementation (in fact i
really would prefer to use a more standard API similar to
Linux/Windows).
2) It seems that only blocking communication (at least waiting 1 ms) is
possible. Any chance to change that? I just avoid this blocking by
having a seperat communication thread.
3) Are there any hints on how to improve the performace; apart from
turning of the buggy full fuplex mode? What is the TCP-Buffer size?
In this Thread this topic is discussed, too. An Example for an UDP Implentation in CVI is attached. Unfortunately it uses the Windows SDK, so it will not work on an RT system.
