QUOTE (Jon Sjöstedt @ Nov 11 2008, 03:34 AM)
The whole idea of polling anything strikes me as an extremely inelegant method. With GPIB, there is ALWAYS a termination character. With 488.2 instruments, it HAS to be EOI. Setting the number of bytes to some arbitrary number has long been an established method. It is certainly much faster than trying to guess the number of bytes and doing some polling. When an instrument has 10 bytes to return, specifying 1000 bytes for the VISA Read has identical behavior to specifying 10.
For queries that might return large data sets, the instrument will often return a header of known size. This header can be read and the number of bytes in the remaining data can be parsed out. Looking at some of the existing instrument drivers will be of great benefit.
