Hal Murray wrote:
[email protected] said:
FTDI devices with their device driver should remember the COM port
they have been assigned on an individual system even if they get
plugged into a different port/hub, and this greatly reduces
reconfiguration effort if you change any USB connections - Other
manufacturer's devices have a tendency to use a new COM port number
each time they are plugged into a different physical USB port
connected to the same computer.
The USB protocol has provisions for each device to provide a
SerialNumber. That lets the OS connect them up at the appropriate
logical name no matter which physical port they are plugged into.
They have been common on disks and thumb drives for a long time. My
printer has one. So does my scope.
Most low cost USB serial adapters don't (or didn't) have a useful
serial number. (Or maybe the Linux drivers don't use it, but I
suspect that's done at a higher level so it should work for serial if
it works at all.)
I have some FTDI adapters that produce useful serial numbers.
usb 3-1: SerialNumber: A4003UAg
usb 5-2: SerialNumber: A4001h2X
I'm pretty sure I have other FTDI ones without a serial number.
On the FTDI website there's a (free) utility called FTProg which can
reprogram the FTDI device.
You can set current limit, invert data lines, change description strings &
serial numbers.
You can even set the serial number to be fixed for a number of similar FTDI
devices so that they will all adopt the same Com port #, which can be
useful, too.
Mike
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