LabVIEW
VISA Read Byte count switching between 2 values
Solved!
You need to either a) end with a termination character enabled, or b) specify a number of bytes to read which is equal or less than the number you send.
In the latter case, you'll read exactly the number of bytes you enter. The VISA Read will trigger a warning, with a message something like "The number of bytes read was exactly equal to the number requested. Ensure that the buffer doesn't still contain more data." Here, you're being told that there might still be more in the buffer to be read, which is exactly what would happen if you read fewer bytes than you send.
In you run this in a while loop, you'll discover that gradually (or perhaps not so gradually) the buffer will fill up with the bytes you're not reading each iteration. This will give you an error about the buffer being full (I think this is output from VISA Write).
The remaining error to consider is that due to timeout - when you set the number of bytes to read to be too high, and don't enable termination characters. In that case, the Read will empty the buffer, but if you don't write more, it will just sit there waiting for the additional bytes. Eventually, it will timeout (10 seconds is the default I believe).
So in conclusion, it's possible to avoid the use of termination characters, but it isn't so straightforwardly simple. Given the choice I would almost always choose to use termination characters. If you're wanting to use the CR and LF characters in the messages you're sending, you can use a different character for termination. If you really want to avoid them entirely (term chars, not CR/LF) then you can use the Bytes at Port to tell your VISA Read how many bytes to read, but now you need to add appropriate Wait nodes, and check more hasn't arrived, and so on.
