Re: Persistent USB serial?
- Reply: Milan Obuch : "Re: Persistent USB serial?"
- In reply to: Milan Obuch : "Persistent USB serial?"
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Date: Fri, 08 Oct 2021 07:25:37 UTC
On Fri, Oct 08, 2021 at 08:00:16AM +0200, Milan Obuch wrote: >Hi, > >I'd like to solicit opinions/hints for following scenario, which is >quite common currently. > >There are some development and evaluation boards designed with USB port >as power source and serial console at the same time (sometimes even >more ports or JTAG as well). When board has power on switch, usually no >activity is present on USB wire without board being powered - there is >some USB-to-UART circuitry powered from board power source. So serial >port device /dev/cuaUn et al. get created only after power on of the >board. > >Problem: port number can be different depending on USB port enumeration >or connection order. Another one: it is easy to miss first characters >sent from the board if you are not able to write required command like >'cu -l /dev/cuaU9 -s 115200' quickly. > >Maybe it is possible to write some devd config file snippet which >ensures consistent device naming without need of maintaining correct >(everytime the same) order of cable connecting, but even that, this >does not solve second problem, starting up some terminal or terminal >like program in time. > >Has anybody some experience in this area who can share it? Some hints >what to test? Do we have some pseudo serial device, which can be used >as device argument for cu command, which can just grab the real USB >serial when it appears on connecting the board under test? > >Regards, >Milan > Hi Milan, There's an open review [1] for location-based unit numbering for USB, which some of us have been using for quite some time - and while it's not completely done, it's very useful. Yours, Daniel Ebdrup Jensen 1: https://reviews.freebsd.org/D21886