From nobody Fri Oct 08 06:00:16 2021 X-Original-To: freebsd-hackers@mlmmj.nyi.freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2610:1c1:1:606c::19:1]) by mlmmj.nyi.freebsd.org (Postfix) with ESMTP id 8BC3312D1433 for ; Fri, 8 Oct 2021 06:00:36 +0000 (UTC) (envelope-from freebsd-hackers@dino.sk) Received: from mailhost.netlabit.sk (mailhost.netlabit.sk [84.245.65.72]) (using TLSv1 with cipher DHE-RSA-CAMELLIA256-SHA (256/256 bits)) (Client did not present a certificate) by mx1.freebsd.org (Postfix) with ESMTPS id 4HQcxH4kbvz3Hxw for ; Fri, 8 Oct 2021 06:00:35 +0000 (UTC) (envelope-from freebsd-hackers@dino.sk) Received: from zeta.dino.sk (fw3.dino.sk [84.245.95.254]) (AUTH: LOGIN milan, TLS: TLSv1/SSLv3,256bits,AES256-SHA) by mailhost.netlabit.sk with ESMTPSA; Fri, 08 Oct 2021 08:00:27 +0200 id 00DCA80D.615FDE7B.00013D06 Date: Fri, 8 Oct 2021 08:00:16 +0200 From: Milan Obuch To: freebsd-hackers@freebsd.org Subject: Persistent USB serial? Message-ID: <20211008080016.7830e3d5@zeta.dino.sk> X-Mailer: Claws Mail 3.18.0git266 (GTK+ 2.24.33; i386-portbld-freebsd11.4) List-Id: Technical discussions relating to FreeBSD List-Archive: https://lists.freebsd.org/archives/freebsd-hackers List-Help: List-Post: List-Subscribe: List-Unsubscribe: Sender: owner-freebsd-hackers@freebsd.org MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit X-Rspamd-Queue-Id: 4HQcxH4kbvz3Hxw X-Spamd-Bar: -- Authentication-Results: mx1.freebsd.org; dkim=none; dmarc=none; spf=pass (mx1.freebsd.org: domain of freebsd-hackers@dino.sk designates 84.245.65.72 as permitted sender) smtp.mailfrom=freebsd-hackers@dino.sk X-Spamd-Result: default: False [-2.10 / 15.00]; RCVD_VIA_SMTP_AUTH(0.00)[]; ARC_NA(0.00)[]; NEURAL_HAM_MEDIUM(-0.80)[-0.802]; FROM_HAS_DN(0.00)[]; TO_MATCH_ENVRCPT_ALL(0.00)[]; R_SPF_ALLOW(-0.20)[+mx]; MIME_GOOD(-0.10)[text/plain]; TO_DN_NONE(0.00)[]; DMARC_NA(0.00)[dino.sk]; RCPT_COUNT_ONE(0.00)[1]; NEURAL_HAM_LONG(-1.00)[-1.000]; MID_RHS_MATCH_FROMTLD(0.00)[]; NEURAL_HAM_SHORT(-1.00)[-1.000]; FROM_EQ_ENVFROM(0.00)[]; R_DKIM_NA(0.00)[]; MIME_TRACE(0.00)[0:+]; ASN(0.00)[asn:5578, ipnet:84.245.64.0/18, country:SK]; SUBJECT_ENDS_QUESTION(1.00)[]; RCVD_TLS_ALL(0.00)[]; RCVD_COUNT_TWO(0.00)[2] X-ThisMailContainsUnwantedMimeParts: N 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