I'm seeing a problem with the number returned by the property node (of a VISA serial port) value Bytes at Port, only on Macintosh OS X (it works fine on Windows).
I'm expecting a reply packet of length 6 from the external device. Indeed, if I write some C code and check, I see 6 bytes waiting, and if I read all available bytes, I get six bytes. (There is no doubt that the device is in fact returning 6 bytes--it's "our" device.)
The property node value Bytes at Port reads 7. If I try to read 7 bytes (VISA Read), I get only 6 bytes and an error code (time out, from waiting for the 7th byte). If I attempt to read 6 bytes, I get the 6 bytes, with an OK, but a warning code that there may be more bytes available (VISA Read must be comparing the Bytes at Port internally, because it appears that there are in fact no additional bytes available).
It appears clear that the Bytes at Port value is off by 1. On the PC, the same LabView code sees 6 bytes waiting, so for now we are working around it by subtracting 1 from the Byte at Port value if we're running on Mac.
Comments?
