Re: resetting a usb com port?

[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.







-- 
Brad Spencer - [email protected]