From mboxrd@z Thu Jan 1 00:00:00 1970 From: Dave Platt Subject: Re: RS232-USB conversion Date: Tue, 18 Oct 2011 14:16:39 -0700 Message-ID: <4E9DECB7.6050500@radagast.org> References: <4E93FBEC.7050907@free.fr> <4E98B35E.1050602@eunet.rs> <4E993C82.2090601@free.fr> <4E9959B1.20704@dommel.be> <4E9DDC6B.8080702@eunet.rs> <20111018212126.3a1053bd.gordonjcp@gjcp.net> Mime-Version: 1.0 Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <20111018212126.3a1053bd.gordonjcp@gjcp.net> Sender: linux-hams-owner@vger.kernel.org List-ID: Content-Type: text/plain; charset="us-ascii" To: Gordon JC Pearce Cc: Miroslav Skoric , linux-hams@vger.kernel.org > If you use a USB-to-serial adaptor, it will appear as something like /dev/ttyUSB0 in Linux. In Windows it's a bit hit-or-miss. Some USB-to-serial adapters (e.g. those from FTDI) come with individual machine-readable serial numbers scribed into each individual chip, which can be read out by the host software. This can be a definite advantage in Linux (and perhaps in Windows as well) because it's possible to arrange for each specific physical USB-to-serial adapter, to be assigned the same device name in /dev each time it is connected. On modern Linux distributions you can use the "udev" scripts to assign a name-alias, if you wish... so, for example, the adapter you have connected to your TNC might always be /dev/ttyTNC0. Without a unique ID in the chip, device-name assignment is much more hit-or-miss. If you have two or more such adapters connected, they may change "names" each time you reboot... it'll depend on just what order your USB hubs and devices are recognized ("enumerated") at boot time. On Linux they'll swap /dev names around, on Windows they will have different "virtual serial port" COM names. The Prolific CP2103 USB-to-serial adapter chips (quite popular) don't generally have IDs in them... I believe this chip *can* be used with an external (I2C or SPI) EEPROM chip that holds an ID, but very few manufacturers use this feature. Interesting note - FTDI now makes a USB-to-serial adapter which is built into a shell that's the same size as a DB-9 male or female PC-mount connector, and has the same pinout. If you have a device which has a DB-9 RS-232 connector mounted on its PC board, you can unsolder this, solder in the corresponding FTDI adapter, and your device now has a USB-serial connection rather than RS-232. Unfortunately they don't seem to make these to fit the older DB-25 connector standard.