PL2303 & gui serial status display for /dev/ttyUSB(x)?

Gene Heskett gene.heskett at
Thu Dec 28 21:43:17 UTC 2006

On Thursday 28 December 2006 11:14, Bob Chiodini wrote:
>I tried a pl2303 serial to USB one and had problems. It was a radio
>shack branded device.

Exactly the same unit here.

>Using FC4 at the time it looked like only every other character was
>being received by the host. Data to the device was fine. Unfortunately,
>I never resolved the problem and opted for a four port Keyspan device.
>No problems connecting through it to the same serial device.

I wonder if possibly the pl2303 driver might have been at fault in the 
older FC4 kernels.  I know its had a couple of patches since then. See 

>If the Garmin only has four wires, most likely the handshake is
>XON/XOFF, if any. Does the Garmin "talk" correctly via one of the "real"
>serial ports?

Apparently so *once* I'd found the option in the Garmins menu's to change 
it from its default protocol to the NMEA protocol.  That was genuinely 
hidden better by far than any Easter Eggs you ever snooped thru a game 

At that point I started to see data, but one way only, on a shack rs-232 
sniffer with all its leds.  But _only_ on its RD led, and I assume if I 
turned the sniffer around (it running on db9-db25 adaptors on both ends 
of it) it would switch to the TD led.  Data in a pattern of off for a 
couple of seconds, blinking for a couple of seconds, then on for a couple 
of seconds, blink till it went back off, repeat forever.  So I don't 
think we are talking to it, just listening.  Which, in the context of 
your quote about every other character getting to the host, does not now 
seem to be the case. ANAICT they are all getting there.

Laying there on a chair seat beside my desk, in a house covered with alu 
sideing, it did finally manage to get a location valid enough to display 
it in roadnav.  This was about in the middle of my downloading the 
TIGERline maps for WV, that I noticed that yellow box & arrow came up.

So, satisfied that it was working, I plugged my x10 stuffs back into ttyS1 
so I had all my outside lighting automation working tonight, changed the 
prefs in roadnav to use ttyUSB0, and plugged it back into the pl2303, and 
its still working!  Based on that it looks like its a go to put this 
thing on my lappy and see if I can get a ticket for driving distracted or 
something, but what I see roadnav as needing next, is the text to speech 
util, so it can say "turn left at the next intersection" just like the 
indash stuff can do.  If the trip is setup ahead of time, this shouldn't 
be *that* hard to do, by whatever means to set it up ahead of time, 
possibly even by entering the stuff from a mapquest query that one would 
normally print, and then get distracted reading it while flyng down 
county road xyz.  Or I-90 for that matter, the point is its a needless 
visual distraction that could kill...

But, its going to need some fuzzy logic/rubber in its calcs too, the green 
bar its drawing as it tracks the gps's reported location is off, or the 
TIGERline maps are off, its showing around 300 feet west of actual, about 
30 feet wide and wandering back and forth about 700 feet in an northwest 
to southeast track.  This gps, a Garmin 12, was made long before the 
noise was turned off that caused the civilian units to be in-accurate 
enough an artillery shell would miss its target harmlessly.  This did not 
change noticeably when I moved it to a windowsill, but its a northern 
facing window.  The signal bars are a lot higher though.  That's a good 
excuse to go get a newer unit I suppose, but for marking a location and 
then taking me back to the same spot, it works quite well, I've found the 
boat dock in the dark several times with it to an accuracy or 30 feet or 
so.  To paraphrase a saying that an ex brother-in-law was famous 
for, "its good enough for the girls I go with" ;)

One thing that roadnav is doing when its set to track the gps, is its 
turning the map so the direction it thinks its going is up, and that's 
distracting while sitting here expecting north to be up. The map suddenly 
looks odd, and north isn't anywhere near up.

In other words, it appears to be working, HOORAY!

Thanks for the incentive to crawl under and try it on a regular serial 
port.  I had about given up & needed a prod in the right direction.  Old 
farts tend to sit there motionless for hours :)


Cheers Bob, Gene
"There are four boxes to be used in defense of liberty:
 soap, ballot, jury, and ammo. Please use in that order."
-Ed Howdershelt (Author) and AOL/TW attorneys please note, additions to the above
message by Gene Heskett are:
Copyright 2006 by Maurice Eugene Heskett, all rights reserved.

More information about the users mailing list