Sending 16 bit Integer by TCP

[Kevin S - Engineer]

I have a program written in JAVA that connect to the TCP server on my labview vi, everything is sending good but I am having a hard time converting the bytes back to an integer.  I beleive it is messing up when sending anyting about 255.  What the VI program does is takes an input signal between 0 - 10 and multiplies it by 1000 and then takes the 16 bit integer value of that and sends it over the TCP connection to my java program.  I had a length of the byte array sent over to but it is always giving me a length of 1 even though it should be 2 if a value of more then 255.  I have attached a copy image of my program, is there a better way to do in?

Thanks

Kevin

[Photon_Dan]

First you convert the waveform data to an array of doubles.  That is OK.  Then you convert the doubles to 16-bit integers.  That will truncate the decimal, but since you multiplied by 1000, I assume you are considering that so that is OK too.  Then you make your  fatal error in wiring the I16 array to a Byte Array to String function.  See that little red dot on the left side if the Byte Array to String function?  That tells you there is a coercion going on that is chopping each I16 down to a U8.  Since you only have 1 integer in your 16-bit array, you end up with only 1 byte in the coerced byte array.

I recommend the Flatten to String function.  It has the option (in newer LabVIEW versions) to change the byte-order (LabVIEW is big endian, but Intel is little endian) and can prepend the array size or not.  Since you seem to want just a single number, you do not want the array size.

See attached example.

Dan Press
PrimeTest Automation

[RavensFan]

You can also do a split number function on the I16 array to come up with two U8 byte arrays.  Interleave those arrays then convert the byte array to a string for sending into the TCP/IP.  You can do all the opposite functions on the other end, though you will need to do a typecast  to conver the resulting U16 to an I16.


Message Edited by Ravens Fan on 07-09-2008 10:23 PM