RS232 from 25pin parallel port?

premelec

Senior Member
My old computer died and I fired up another old computer which doesn't have D9 serial but does have parallel port D25 - showing up as COM3 and works on a printer... I tied wiring a stereo plug to 25 Pin 3 - 2 - 7 RD-TD-SG [2-3-5 RD-SD-SG ON D9] - didn't work - I tried reversing 2 & 3 and that also didn't work [I didn't think it would...].

Is there some reason I can't use D25 pins to program my PICAXEs? I tried various USB to D9 converters which also don't work - I've got an old laptop that I can use but am wondering why the parallel port doesn't work...

Thanks!

PS Plug - [hope I got that right!]
TIP=Ground
RING=SERIN
SLEEVE=SEROUT
 
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john2051

New Member
Hi, sounds like a duff serial port! There is software around for testing serial ports with loopback
plugs, but it depends which operating system you're using.
Good luck, regards john
 

Buzby

Senior Member
Are you sure the D25 is serial, not parallel ?.

Some old PCs used D25's as parallel ports.

You said it drives a printer. What connector is on the printer end of the cable ?
If it's a 36 way Centronics then it's not serial. See http://www.lammertbies.nl/comm/cable/parallel.html

Also, you said it shows as COM3. Where are COM1 and COM2 ?
 

Goeytex

Senior Member
Try a loopback test by connecting pins 2 & 3 together. That should confirm a duff port.

You are calling it a parallel port but my guess is that it is a DB25 serial port found on some older computers. If it is indeed a parallel port, it will not work with a Picaxe.

Is this com port integrated on the system board or is it on an add-on card? I am assuming you are running XP or higher ?

If there is no Com1 or Com2 shown in device manager then possibly you can enter the system bios setup and check the settings. If you disable the parallel port in the system bios does the printer stop working?

Check the printer settings in the operating system, Is it attached to LPT1 or to Com3 ?

This must be a really old computer ?
 
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westaust55

Moderator
This must be a really old computer ?
How old is "really old"?
I had two home PC's using ASUS A7N8X-E mobos.
http://dlcdnet.asus.com/pub/ASUS/mb/socka/nforce2/a7n8x-e/e1876_a7n8x-e_deluxe.pdf
About 7 to 8 years old but still had serial (9-pin) + parallel (25-pin) ports, 2 Ethernet as well as IDE and SATA.

Alas, a few weeks back ( at the time of a severe lighting storm directly over the house) just when lightning detectors were being discussed on this forum, one of my mobo's failed :(
So still one "really old PC" but now also one with the the very latest technology. :)
 
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premelec

Senior Member
Buzby - thanks for reminding me that - yes it's a parallel port so not going to send RS232 !

Computer that died was HP - 10 years old and this 'new' HP only about 6 years old - free on the street. Maybe I'll get an RS232 card to plug in.

Thanks for all the remarks... maybe I can find a USB to 232 that works ok - one that I tried worked and then got unstable interfering with mouse and such - several just didn't do anything... I'll dig up Stan's famous 'always works blue wonders' ref... :)

Westy - sorry about your loss... lightening season coming in here now - I unplug everything and have a cool drink when I hear thunder [unless I'm bicycling - then I pedal like hell...].
 

SAborn

Senior Member
Your best bet is to buy a $3.00 blue cable and move up to usb, you will need to do it sooner or later.

Here is a link to the blue cables i have used dozens of, it uses the HL340 driver which is supplied on disc, and from what im told win7 has the driver in its default menu.

http://www.ebay.com.au/itm/250512172218?ssPageName=STRK:MEWAX:IT&_trksid=p3984.m1438.l2649#ht_3821wt_932

It might list not compatable with Vista or win7, but the driver and cables work fine with all Windows OP systems of 32 bit.
 

premelec

Senior Member
@ SAborn... I bought this item http://www.ebay.com/itm/170434463723? and downloaded recommended drivers - didn't work - yet... I looked back at manuka's comments but it's hard tell from the ebay pix what's inside... so I ordered a unit that's open chassis shows IC & xtal [$3]. Anyhow I'm wondering if the model you refer to needs a driver in XP? I have a couple of other things besides PICAXE that need the D9 connection... Thanks for your suggestion!

@Buzby... I've got a Compaq SR1630NX desk top unit - it seems some of these had D9 some not... mine not and indeed was damaged when I got it off street - Video connector torn off - took me a few hours to get that working again... There are a couple of card slots I can use. Am running XP SP2... looks like I could get a dual RS232 card for less than $15. I like USB fine when it works - though USB 1 is way too slow [It took a whole day to offload 40GB from an old HP to an external drive USB 1 connection!]
 

bpowell

Senior Member
I like USB fine when it works - though USB 1 is way too slow [It took a whole day to offload 40GB from an old HP to an external drive USB 1 connection!]
USB 1 is 1.5 Mb/s at low-bandwidth...that's still faster than any serial comms you'll be doing with the PICAXE...
 
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