Re: resetting a usb com port?

Brad Spencer wrote:
> [email protected] (MLH) writes:
> 
> > I am programming some esp32s and every now and then the port locks up from
> > an error and I can't find a way to reset it properly.
> >
> > For example:
> >
> > [ 651173.2591532] uchcom0 at uhub1 port 9
> > [ 651173.2591532] uchcom0: QinHeng Electronics (0x1a86) USB Serial (0x7523), rev 1.10/2.64, addr 3
> > [ 651173.2691535] ucom0 at uchcom0
> > [ 651197.0392490] ucom0: detached
> > [ 651197.0392490] uchcom0: detached
> > [ 651197.0392490] uchcom0: at uhub1 port 9 (addr 3) disconnected
> > [ 651204.6892798] uhub1: device problem, disabling port 9
> > [ 651246.6894490] uhub1: device problem, disabling port 9
> > [ 651247.2094511] uhub1: device problem, disabling port 9
> >
> > Is there a way to reset ucom0 without having to reboot ?
> >
> > Thanks
> 
> 
> The above messages look like a clean detach followed by the complaint,
> but since there was a complaint it suggest that the USB hub has gotten
> unhappy with the device attached to the port and has disabled that port.
> It might not be possible to soft recover from this situation and even a
> physical removal and reinsertion may not help.  A number of things could
> be going on here anything from a poor quality cable, to a poor quality
> USB device to some sort of power blip due to the power draw on the tty
> serial side or even something a little off with the computer USB port
> itself.  Inserting a self powered hub between the computer and the
> device might help, at least with anything except a bad cable.  To be
> clear, I mean a hub with its own power supply.  Usually something simple
> is best.  If you can try a different ucom chip it might help.  I have
> had really good luck with anything from FTDI.  There is a considerable
> amount of Just Plain Strange going on with USB devices and you might
> have to experiment.

Thanks very much!!  Greg's suggestion of using an externl usb hub
worked!!