From mboxrd@z Thu Jan 1 00:00:00 1970 From: Rodolfo Brasnarof Subject: Re: Hamlib: "ppdev0: claim the port first" Date: Wed, 27 Jul 2005 09:00:48 -0300 Message-ID: <20050727090048.5b0d92b2.rodob@datafull.com> References: <40764501050726193096edae3@mail.gmail.com> <200507271513.37262.w.knol@niwa.co.nz> <4076450105072620427655487b@mail.gmail.com> Mime-Version: 1.0 Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <4076450105072620427655487b@mail.gmail.com> Sender: linux-hams-owner@vger.kernel.org List-Id: Content-Type: text/plain; charset="us-ascii" To: Linux Hams Cc: Jonathan Lassoff On Tue, 26 Jul 2005 20:42:38 -0700 Jonathan Lassoff wrote: > On 26/07/05, Wilbert Knol wrote: > > A level converter designed to work with EIA232 ports won't work on a > > parallel port. They are different beasts with different voltage > > levels and pin-outs. > > ... > > Hope this helps. > > > > Wilbert, ZL2BSJ > > I realized about 10 minutes after sending that message that I made a > mistake as to the different device architectures. Is there any > crossover between the the parallel port design and the older RS-232 > ports? Does the parallel port actually send the same data? Yes, but they work in a totally different way. Serial port sends it's data one bit at a time through the tx line, and parallel sends it all bits at the same time, using different lines. Many applications don't even use the serial port as a serial device (transmitting data) but as a control device (such as soundmodem ptt control). In those cases, they generally use handshaking lines, instead of data lines. In those cases, you could use a parallel port, if the application can support it. > The level converter uses the voltage from the DTR and RTS through a > 5V regulator to power an IC that converts the TTL voltages to RS-232 > levels and vice versa. Anyone have thoughts on the matter? I don't understand if you need ttl levels output or rs-232 level output. Standard serial port uses rs-232 levels. If you need ttl levels, you need a converter. Parallel port, on the other hand, uses ttl levels. So, if your application supports using a parallel port, you don't need a converter. Notice that your program must have support for it, and cabling is different.