I am attempting to communicate with a Neslab Chiller. The instrument takes hexadecimal commands. In NI VISA Interactive Control I am able to communicate and get the correct responses back from the instrument. Unfortunately, when I attempt to communicate in labview using VISA read and write I keep getting a VISA read error (a timeout error) and the instrument cannot be controlled. I know there is some weird catch with having to different programs calling the same instrument, so I make sure every time to just labview open and not NI VISA Interactive Control. I also am very careful to match the baudrate, parity, last bit, and end mode for the read and write commands. I have attached images of the NI VISA Interactive Control Settings that were successful as well as my thus far unsuccessful labview vi. Please help me! Thank you in advance!

@arwc wrote: Here is the manual for my instrument http://www.idealvac.com/files/manuals/Chiller_Neslab_ThermoFlex-900-2500_Manual.pdf I'll try to help out. I don't have a NESLAB Chiller so I cannot vouch that these snippets will work. You will have to iron out the details. From what I seen in the manual, the chiller does not use a termination character. You do not need to add one. The length of the message is embedded in the command. This is how I would build up the command syntax that the master would send. Reading the response from the slave is a little bit trickier since it does not send a termination character (make sure you DISABLE the TermChar when calling the VISA Config VI), but it has a well defined format for the response. First read in the preamble (first four bytes). Then read one byte to calculate the number of bytes to follow. Convert that hex string to an unsigned intereger and use that value to read in all the remaining data. Lastly you have an extra 1 byte to read to get the CRC checksum.

LabVIEW

Visa Serial Control

Solved!

Author

Thank you everyone for your help, jamiva especially! For reference I did change the u32 to a u8 in the program jamiva provided to reach success. Also, the VISA serial configure did work better than the property node, so thank you ravensfan as well.

Message 21 of 21

(625 Views)

LabVIEW

Visa Serial Control

Re: Visa Serial Control