How can detect the serial port is active

[Zoyo]

I made a program. It can read datas via serial port. But the datas wont came all the time, so the other part of the program not need to run. I want to put before the "reading serial port" a detection about the serial port is get a data. So the reading is wont start before datas are not coming. Can anybody help me how can i solve this problem?

[daveTW]

Hi Zoyo, if you use the VISA- VIs, the functionyou need is "VISA Bytes at serial port". It shows, how many Bytes are available in the input buffer. You can find it here:



greets, Dave

Message Edited by daveTW on 11-22-2006 02:01 PM

[James_R]

You can also use events along with the bytes at port so you don't have to poll the bytes at port so often.  see the attached image

-James

Message Edited by James R on 11-22-2006 09:06 AM

[Steve.Briggs]

What function is that coming after the cluster in the Rx Data Loop?

[James_R]

This example uses queues to store the data until it is processed in the parallel loop.  the function after the cluster is enqueue element found in programming>synchronization>queue operations

-James

[Zoyo]

Thx for all. I try to do it now.

[Zoyo]

James:
Can U attach the vi file about serial_interrupt ?

[Zoyo]

daveTM: So it's mean if the VISA Bytes at serial port value is 0, than the datas are not coming? Because if it's true I can put my whole program int Case Structure and i can say if the value is 0 do not doing anything, and if the value is bigger than 0, than wich program must to work.

[daveTW]

Sorry for the late answer.
Yes, you're right, if this function gives a value back greater than zero, there was something received by your serial port. The NI- serial driver handles the serial protocol for you automatically and stores the received bytes in a buffer. When you use "VISA Read" this function only gives back the data of this buffer. So you don't have to read every single byte by byte but can wait until a certain amount of bytes are received and read them in one.
Greets, Dave