Date: Tue, 1 Jul 2008 13:16:50 +0200 From: "Werth, Volker" <v.werth@bally-wulff.de> To: "Rohit Grover" <rgrover1@gmail.com> Cc: Volker <volker@vwsoft.com>, freebsd-embedded@freebsd.org Subject: Re: having trouble receiving serial data using my USB->serial adaptor Message-ID: <200807011316.50422.v.werth@bally-wulff.de> In-Reply-To: <426bed110807010301j132a75f4q1c85fce62ca85188@mail.gmail.com> References: <426bed110806300025j5a92080bx59cdb2248c77b8c0@mail.gmail.com> <4869337C.6050105@vwsoft.com> <426bed110807010301j132a75f4q1c85fce62ca85188@mail.gmail.com>
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Volker Werth schrieb am 01.07.2008 13:16 _____________________________________________________________________ Am Dienstag, 1. Juli 2008 12:01 schrieb Rohit Grover: > Hi, > > Thanks for the response. I stumbled upon the solution quite by chance. > > My USB->serial adaptor has a NULL modem built into it, so attaching an > external NULL modem was un-necessary and incorrect. It is a wonder = that the > devices survived this treatment. > > thanks again. > > regards, > > > > I am having trouble getting my BAFO 810 USB->serial adaptor to > > > work. I have built the uplcom and ucom drivers into the kernel, > > > and my USB->serial adaptor is recognized at boot, as can be > > > inferred from the following lines from /var/run/dmesg.boot: > > > > > > ucom0: <Prolific Technology Inc. USB-Serial Controller, class > > > 0/0, rev 1.10/3.\ 00, addr 2> on uhub3 > > > > > > I am using minicom to drive /dev/cuaU0 at 115200 8N1. > > > > > > If I connect the Tx and Rx lines (pins 2 and 3) of the DB9 > > > connector, I can get echoes of my keystrokes on the minicom > > > terminal. > > > > > > Unfortunately, I am unable to connect to an embedded device which > > > supports serial connections at 115200 8N1. When I plug the serial > > > output connector of my adaptor to a NULL modem and then to the > > > target embedded system, I don't see any serial output from the > > > device on my minicom terminal. This same device communicates > > > correctly with the serial port of my linux desktop with minicom > > > and 115200 8N1. > > > > > > As a further experiment, I manually connected pins 2,3, and 5 of > > > the serial end of my adaptor to pins 3,2, and 5 respectively of > > > the embedded device, but still no luck. > > > > > > What am I missing? > > > > > > regards, > > > > Rohit, > > > > hard to tell on the distance but if you're able to receive (using a > > loopback adapter), it sounds like either side is most likely = requiring > > hardware handshake (DSR/DTR, RTS/CTS). > > > > Sometimes it helps to short cut the DCD line (to RTS/DSR), as some > > device refuse to send if DCD is not set. If you're owning a break = out > > box, it should be snap to figure that out. At least you should check > > using a serial line tester (those little tools signaling line status > > using LEDs or use a Voltmeter to check for correct line status). > > > > Volker Rohit, correct terminology is: Instead of the usual DTE (provided by built-in = PC=20 serial ports), your adapter is a DCE. Connecting that to a DTE (modem, = serial=20 terminal) does not require a null-modem (crossed Rx/Tx, handshake) = cabling. Connecting DCE to DCE or DTE to DTE always requires a (crossed) null = modem=20 connection. DTE to DCE requires a straight 1:1 cabling. Against everybody's assumption, a PC's serial port is mostly always a = DTE. I=20 think this may go back to the time (some 20 or 30 years) while PCs were = seen=20 just as smart (dumb?) terminals connected to a mainframe. HTH Volker --=20 Volker Werth system engineering Bally Wulff Entertainment GmbH Maybachufer 48-51 12045 Berlin, Germany ph: +49(30)62002-109 Bally Wulff Entertainment GmbH, Maybachufer 48-51, 12045 Berlin, = Postanschrift: Postfach 44 01 57, 12001 Berlin Tel.: 030-620 02-0 FAX: = 030-620 02-200, Gesch=E4ftsf=FChrer: Sascha Blodau, Wolfram J. Seiffert, = Tim Wittenbecher, Amtsgericht Berlin-Charlottenburg, HRB 91532 B, UST-ID = DE 234 517 998 _____________________________________________________________________ Dieses E-Mail ist nur f=FCr den Empf=E4nger bestimmt, an den es = gerichtet ist und kann vertrauliches bzw. unter das Berufsgeheimnis fallendes Material enthalten. Jegliche darin enthaltene Ansicht oder Meinungs- =E4u=DFerung ist die des Autors und stellt nicht notwendigerweise die Ansicht oder Meinung von Bally Wulff Entertainment GmbH dar. Sind Sie nicht der Empf=E4nger, so haben Sie diese E-Mail irrt=FCmlich erhalten und jegliche Verwendung, Ver=F6ffentlichung, Weiterleitung, Abschrift oder jeglicher Druck dieser E-Mail ist strengstens untersagt. Weder Bally Wulff Entertainment GmbH noch der Absender (Volker Werth) =FCbernehmen die Haftung f=FCr Viren; es obliegt Ihrer Verantwortung, die E-Mail und deren 0 Anh=E4nge auf Viren zu pr=FCfen. 0 Anh=E4nge: _____________________________________________________________________ Versand am 01.07.2008 13:16 von Werth Volker
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