Serial Port write/read very slow.......solutions???

[PaceLT1]

Hello all...

I am writing a Labview (7.1) program to communicate with an automotive scantool (ElmScan 5).  It bascially consists of reading and writing HEX values.  I have written a program to display the RPM of my car, but for some reason, the refresh rate is very slow.

When I hook it up to my car, it only shows a new value at about 4 Hz (about 4 readings per second), which is not nearly as fast as I need it to be.  It might have something to do with the error that I'm getting (the error code I'm getting is 1073676294, and it's located @ "VISA Read in SerialCommRPM.vi", but it will still take correct readings even with the error, so I can't figure out what's wrong.   

I have the indicators on synchronous display and the serial write/read is also on synchronous.  I am operating the port at 9600 baud (I don't know if the scantool will work properly on any other rate).  I tried taking everything out of the loop that didn't need to be there, but it didn't help at all. 

I can't figure out why it will only take about four readings a second.  Is it the error, or the baud rate, or the serial write/read, or is there something about my loop that is causing it to be so slow?  I have attached the VI.  Thanks in advance for any help.

[Albert.Geven]

Hi

It is not an error, it is a stupid warning that you got what you asked. I normally want to suppress this info.

It is nice when setting up a system but when it works it is fine.

Maybe you can put your instrument in a write always mode, so that you don't have to ask for the data, and

maybe the instrument does not send this information faster.

You can look with an oscilloscope on the serial line to see where the speed is lost but 4 times a second is not abnormal for rpm