Skip site navigation (1)Skip section navigation (2)
Date:      Mon, 14 Jul 2008 21:05:12 +0100
From:      spellberg_robert <emailrob@emailrob.com>
To:        fbsd_chat <freebsd-chat@freebsd.org>
Subject:   Re: 50 baud is dead
Message-ID:  <487BB178.90000@emailrob.com>
References:  <g58mmb$16sj$1@kemoauc.mips.inka.de>	<200807121018.39240.doconnor@gsoft.com.au>	<g5a2p4$1uuu$1@kemoauc.mips.inka.de>	<200807131004.43681.doconnor@gsoft.com.au>	<alpine.BSF.1.10.0807130945370.94782@wonkity.com> <487A32BB.1040306@telenix.org>

next in thread | previous in thread | raw e-mail | index | archive | help
Chuck Robey wrote:
> -----BEGIN PGP SIGNED MESSAGE-----
> Hash: SHA1
> 
> Warren Block wrote:
> 
>>On Sun, 13 Jul 2008, Daniel O'Connor wrote:
>>
>>
>>>On Sat, 12 Jul 2008, Christian Weisgerber wrote:
>>>
>>>>Daniel O'Connor <doconnor@gsoft.com.au> wrote:
>>>>
>>>>>>It turns out that uplcom(4) adapters don't support the required
>>>>>>speed of 50 baud anymore.
>>>>>
>>>>>You know, it might actually support it if you hack up the driver.
>>>>>The source says the PL2303X "can set any rate".
>>>>
>>>>The data sheet disagrees.
>>>>
>>>>"The flexible baud rate generator of PL-2303X could be programmed to
>>>> generate any rate between 75 bps and 6Mbps."
>>>
>>>I guess you're out of luck then :(
>>
>>Or just try it at 75 and see if there's enough slop to read the 50 baud
>>data.
> 
> There won't be, 50% is way too far off, I think (from experiments I did 30 years
> back) that about 12% is the limit, when I had access to the best regenerators.
> Regens don't even get used anymore.  I forget the actual limit I probed, but I
> know 1/2 over is way too far to go.
> 
>>-Warren Block * Rapid City, South Dakota USA



first, in very round numbers,
   you get about five per cent error in the bit_time
   for fifty per cent error in ten bits.
usually, there are three reads, all near the center of the bit_time.
so, ya gotta be kinda close.
two per cent leaves plenty of room for slop.

i have an inexpensive hardware solution.

if any one is interested, please respond off_list, unless
   you think it appropriate for -chat.

rob




Want to link to this message? Use this URL: <https://mail-archive.FreeBSD.org/cgi/mid.cgi?487BB178.90000>