From mboxrd@z Thu Jan 1 00:00:00 1970 From: Dave Platt Subject: Re: USB converters and old hardware (Baycom in particular) Date: Thu, 15 Apr 2010 13:41:58 -0700 Message-ID: <4BC77A16.3050804@radagast.org> References: <201004081508.45770.phillor@telstra.com> <20100413135239.89243vh5ioxdtks0@mgtmail.com> <201004151151.38923.phillor@telstra.com> <20100415104942.63522s5vbiv7a7i8@mgtmail.com> <4BC75156.9060907@radagast.org> Mime-Version: 1.0 Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: Sender: linux-hams-owner@vger.kernel.org List-ID: Content-Type: text/plain; charset="us-ascii" To: linux-hams@vger.kernel.org Adam Sampson wrote: > Dave Platt writes: > >> I'm not sure how this is being done... but it may not be possible at >> all in a USB dongle! > > You might be pleasantly surprised. The FTDI USB-to-serial chips have a > bit-banging mode that's designed for doing this sort of thing, where you > can tell it to just clock a sequence of bits out to the pins (or read > one in) at a fixed rate. It'd need some software fiddling, of course, > and if you're going to that much effort I'd be tempted just to stick a > microcontroller in the way to give the modem a more convenient serial or > USB interface... You're right, I hadn't thought about those particular USB chips in this context. They would require something other than the standard serial-port host driver (i.e. a special driver, or at least some specialized ioctls or other modes in the existing driver) since they aren't being used as UARTs. Yes, sticking a microcontroller between the modem chip and the USB would certainly ease things. That's the approach that the TNC-X takes... it's a PIC micro hooked to a modem chip, which then connects either to a serial port or to an on-board FTDI serial-to-USB interface. It speaks KISS over the host interface, and is thus fairly easy to support on the host side.