[GreenKeys] Current Loop to RS-232 Conversion on ASR33
COURYHOUSE at aol.com
COURYHOUSE at aol.com
Mon Mar 18 23:08:57 EDT 2013
Christian - no the term type for tty would overprint on the hp
2000 as I remember
In a message dated 3/18/2013 8:05:47 P.M. US Mountain Standard Time,
captainkirk359 at gmail.com writes:
Wouldn't computer systems have trended to run an attached '33 as a full
duplex terminal?
Mostly the reason I can see that is for user logon password protection.
(Don't echo back the password.)
If the terminal is run half-duplex the terminal needs work arounds -- see
for example the IBM 2741's commands to disable printing.
Cheers,
Christian
On 18 March 2013 22:45, Don Robert House <_k9tty at dls.net_
(mailto:k9tty at dls.net) > wrote:
Rob,
ASCII 67 is an 11 unit code. 1 Start, 8 data bits, 2 Stop. However the
8th data bit is used for parity.
Since your machine is printing in local you must have a nicely operating
machine.
I have never seen a 33 operate in Full Duplex, but it should certainly be
possible.
The 32, 33, and 38 generate characters in parallel and are serialized by
the distributor.
Your problem is located somewhere incoming to the selector magnet when the
switch is in the Line position.
Your message reads that the machine is not running open so the selector
has constant current in it's winding.
I have some schematic drawings for the 33, but I need to know what model
you have.
There should be a sticker on the rear of the base near the call control
unit.
Don
K9TTY
On 16 Mar 2013, at 3:19 PM, Rob Jarratt wrote:
It has been a little while since I looked at my ASR33 problem. Just to
refresh everyone: In Online mode I can send characters from the ASR33 to the
computer, but the characters coming back do not print. It works perfectly in
Local mode. I have checked and it is full duplex 20ma, which matches the
setup of my current loop converter and I am using 110bps, 7 data bits, 2
stop bits and Even parity. The ASR33 does not chatter (run open) when
connected to the converter.
Today I tried sending a break from the PC to the Teletype. It did not
chatter when I sent the break. I verified with a multimeter that the current
goes to zero, so I am definitely sending the break.
Does this offer any clues?
Regards
Rob
From: Alf Fisher [_mailto:alf_fisher at tiscali.co.uk_
(mailto:alf_fisher at tiscali.co.uk) ]
Sent: 24 February 2013 21:39
To: _r.jarratt at computer.org_ (mailto:r.jarratt at computer.org) ;
'Teletypeparts'; _greenkeys at mailman.qth.net_ (mailto:greenkeys at mailman.qth.net)
Subject: Re: [GreenKeys] Current Loop to RS-232 Conversion on ASR33
Hi Rob,
I'm sure others will agree but I believe the ASR33 doesn't actually need a
high voltage source as there is a transistor circuit that actually drives
the electromagnet. I reckon 20 volts with a resistor to limit the current
to 20 mA should work.
Is it possible with the Westermo, to loop-back the TTY to itself so you
can print what you type? I don't know what is in the converter but another
way may be to bridge the Tx & Rx pins on the Westermo RS232 port (pins 2 &
3?). It should work the same as being in Local but you are switched to
Line.
Alf
----- Original Message -----
From: _Rob Jarratt_ (mailto:robert.jarratt at ntlworld.com)
To: _r.jarratt at computer.org_ (mailto:r.jarratt at computer.org) ;
_'Teletypeparts'_ (mailto:teletypeparts at aol.com) ; _greenkeys at mailman.qth.net_
(mailto:greenkeys at mailman.qth.net)
Sent: Sunday, February 24, 2013 11:55 AM
Subject: Re: [GreenKeys] Current Loop to RS-232 Conversion on ASR33
I have not looked at this problem for a week or so but will be looking
again today. To summarise, I can send characters from the Teletype to my
computer successfully, but any characters I send from the computer to the
Teletype do not print out.
So far I have verified that the ASR33 is wired for 20ma Full Duplex and
that my Westermo converter works, because I can connect up the current loop
interface into a loopback configuration and I get the characters I send on
the RS232 side echoed back. I am using my RS232 port set at 110bits/sec, 7
data bits, 2 stop bits and even parity. The battery test suggested by
Teletypeparts has not worked though. The only things I have yet to check are:
1. Is the mode relay inside the CCU is operating correctly? I used a
multi-meter to test that the contacts were made and broken correctly. It
looks to be making and breaking contacts OK for the most part. One of the
contacts (AM-15) seems a little bent, requiring the relay to close
completely to break the contact. As the bend was such that the contact might not
open correctly, I tried isolating it with some paper, but it didn’t seem to
make any difference. A couple of contact pairs showed shorts regardless of
the relay position, but the relay was fully wired in, so this might be
expected. The constantly shorted pairs are AM-9 with AM-8, and AM-1 and AM-2. Is
there a simple way to test the relay with a battery? I am not sure what
voltage and current it would need.
2. The voltage provided by the converter. I am told it needs to be
80V and some converters do rather less, perhaps 20V. I have a multi-meter,
but in this case I am not sure where to measure the voltage, I have tried T+
and T- with respect to the converter’s Shield connection and with respect
to the TTY’s earth but I don’t get any more than about 1 volt, this is
whether I am sending characters or not.
Any ideas?
Regards
Rob
From: _greenkeys-bounces at mailman.qth.net_
(mailto:greenkeys-bounces at mailman.qth.net) [_mailto:greenkeys-bounces at mailman.qth.net_
(mailto:greenkeys-bounces at mailman.qth.net) ] On Behalf Of Rob Jarratt
Sent: 10 February 2013 23:10
To: 'Teletypeparts'; _greenkeys at mailman.qth.net_
(mailto:greenkeys at mailman.qth.net)
Subject: Re: [GreenKeys] Current Loop to RS-232 Conversion on ASR33
I tried a loopback test on my Westermo converter and that worked fine when
looping back from PC back to PC through the current loop. I tried looping
back from the TTY side via the RS232 interface and there was no echo.
I then tried the battery test you mentioned and unfortunately that failed
to work too.
I think the problem must be inside the 33. L
Regards
Rob
From: Teletypeparts [_mailto:teletypeparts at aol.com_
(mailto:teletypeparts at aol.com) ]
Sent: 10 February 2013 22:28
To: _r.jarratt at computer.org_ (mailto:r.jarratt at computer.org) ;
_greenkeys at mailman.qth.net_ (mailto:greenkeys at mailman.qth.net)
Subject: Re: [GreenKeys] Current Loop to RS-232 Conversion on ASR33
Rob,
I have heard of the interfaces being bad but I am afraid I have exhausted
my limited knowledge of interfacing. Some of the guys on Greenkeys may be
able to help you.
If you want to eliminate the 33 as a problem completely do the following:
Short together 4 and 6 and apply a 9 volt batt to 3 and 7. Again, if it
runs open reverse polarity on 3 and 7. Do the test in Line mode. After
you have the 33 running closed, type a few characters. If they print OK the
trouble is not in the 33. I still dont recommend leaving the batt on very
long. A minute or so. It may not harm anything, but just to be sure keep
the time short.
What you have done is make the 33 half duplex (2 wire) and tested it in
line mode. I do that all the time here to check out the 33 in Line mode. I
also use a test generator, but before I had that I used the 9 volt batt
test.
Wayne
-----Original Message-----
From: Rob Jarratt <_robert.jarratt at ntlworld.com_
(mailto:robert.jarratt at ntlworld.com) >
To: 'Teletypeparts' <_teletypeparts at aol.com_
(mailto:teletypeparts at aol.com) >; greenkeys <_greenkeys at mailman.qth.net_
(mailto:greenkeys at mailman.qth.net) >
Sent: Sun, Feb 10, 2013 4:28 pm
Subject: RE: [GreenKeys] Current Loop to RS-232 Conversion on ASR33
I do understand about the echo that is needed to get characters to print
in line mode. I am using a terminal emulator on the PC to receive and
display the characters I type on the ASR33, and I type characters into the
terminal emulator to send them to the ASR33 in the hope they will be printed. The
emulator successfully displays the characters I type into the ASR33, but
the ASR33 does not print the characters I type into the emulator, despite
the Westermo LEDs showing activity which suggests it is receiving the
characters from the emulator and sending them on to the ASR33.
I had to re-read about start bits because I had forgotten about them. I
think start bits are always present, so there is no setting to control them.
So basically, I think I am already using 1 start bit, 7 data bits, one
parity bit and 2 stop bits, but nothing is getting printed. I am using a line
speed of 110 bits/sec, which in this case corresponds to 110 baud too.
I suppose the Westermo converter could be faulty and not sending data out
to the ASR33. Unless anyone has any other suggestions I’ll try a loopback
test on the converter to see if it is working.
Regards
Rob
From: _greenkeys-bounces at mailman.qth.net_
(mailto:greenkeys-bounces at mailman.qth.net) [_mailto:greenkeys-bounces at mailman.qth.net_
(mailto:greenkeys-bounces at mailman.qth.net?) ] On Behalf Of Teletypeparts
Sent: 10 February 2013 18:20
To: _r.jarratt at computer.org_ (mailto:r.jarratt at computer.org) ;
_greenkeys at mailman.qth.net_ (mailto:greenkeys at mailman.qth.net)
Subject: Re: [GreenKeys] Current Loop to RS-232 Conversion on ASR33
Rob,
Read on as I put something important below.
I guess the voltage doesnt need to be 80 or more. It may run OK with
less. The norm is 20 MA at 120 VDC.
I dont know anything about the Westermo, but I know that when you send to
the computer from the 33 the computer needs to be programmed to echo back
to get a copy on the 33.
When you type in Local, the print is pretty much instant. When you type
in Line thru the computer you will see a slight delay, not much but enough
to notice.
The 33 doesnt care about parity on its receive side, it will print
whatever the bits from 1 to 7 are. The 33 is 110 baud, not sure what that
converts to in computer language.
Oh and this is important, you need a START bit which is always a zero or a
space or no current which all terms seem to be interchangeable. The rest
you got correct. Its one start bit, 7 data bits, one parity bit and 2
stop bits. The 33 will run with 1 stop bit, but its normal to give it two
when you can.
If you put the START bit in, I bet it will work.
Wayne
-----Original Message-----
From: Rob Jarratt <_robert.jarratt at ntlworld.com_
(mailto:robert.jarratt at ntlworld.com) >
To: 'Teletypeparts' <_teletypeparts at aol.com_
(mailto:teletypeparts at aol.com) >; greenkeys <_greenkeys at mailman.qth.net_
(mailto:greenkeys at mailman.qth.net) >
Sent: Sun, Feb 10, 2013 5:36 am
Subject: RE: [GreenKeys] Current Loop to RS-232 Conversion on ASR33
I made some great progress, with one last hurdle to overcome.
I configured the Westermo to be in active mode (ie supply current) on both
its receive and transmit sides). This cured the problem with the RD light
on the Westermo being on all the time and it stopped the chattering too.
I connected it up to a terminal emulator running on my PC. When I press a
key on the ASR33 the corresponding character appears on the terminal
emulator. However, when I try to send characters from the terminal emulator to
the ASR33 nothing happens. I am using 110bps, 7 data bits, even parity and 2
stop bits.
As the chattering has stopped, does this mean that the Westermo’s transmit
side is set up correctly now?
Am I using the right serial port settings?
Could the Westermo not be outputting the right voltage? It is a 20ma
interface, but the manual does not say anything about the voltage which you say
needs to be 80V or more.
What else might prevent the characters from being printed out?
Regards
Rob
From: Teletypeparts [_mailto:teletypeparts at aol.com_
(mailto:teletypeparts at aol.com?) ]
Sent: 09 February 2013 20:30
To: _r.jarratt at computer.org_ (mailto:r.jarratt at computer.org) ;
_greenkeys at mailman.qth.net_ (mailto:greenkeys at mailman.qth.net)
Subject: Re: [GreenKeys] Current Loop to RS-232 Conversion on ASR33
Rob,
The 33 should chatter or run open when in Line mode and not connected to
anything. The reading of a short is normal as on 3 and 4 you are basically
looking at a switch, the distributor of the 33. Same reading on 6 and 7
as I recall.
Neither side of the 33 generates any current. The receive wants 20 MA at
80 volts or more and the send will accept whatever the interface gives it,
usually 12 or 15 volts.
A quick test you can do is wire a 9 volt batt to 6 and 7 while in line
mode. You have a 50/50 chance of getting the polarity correct. If still
running open, reverse the leads. The 33 should run closed. Dont leave the
batt connected for a long time. You have now verified the 33 will run closed
in Line mode and you need to proceed with the adapter stuff of which I
know very little.
I believe the Send side of the Westmo should be set to active to generate
20 MA current for 6 and 7 of the 33.
Dont know about the Westmo receive side.
Hope this helps,
Wayne
-----Original Message-----
From: Rob Jarratt <_robert.jarratt at ntlworld.com_
(mailto:robert.jarratt at ntlworld.com) >
To: greenkeys <_greenkeys at mailman.qth.net_
(mailto:greenkeys at mailman.qth.net) >
Sent: Sat, Feb 9, 2013 7:22 am
Subject: [GreenKeys] Current Loop to RS-232 Conversion on ASR33
I emailed this list a little while ago about getting my ASR33 to talk
RS-232. I have since sourced a Westermo MA-21 current loop converter.
I have noticed however, that the ASR33 will “chatter” in line mode
regardless of whether the current loop wires are connected to anything or not.
When I plug it into the Westermo the RD light on the Westermo comes on even
if the ASR33 is disconnected from the mains. The RD light is supposed to
come on when it is receiving data from the line interface (manual here if you
want to see it: _http://www.westermosales.com/pdfs/MA-21manualENGSEDE.pdf_
(http://www.westermosales.com/pdfs/MA-21manualENGSEDE.pdf) ), which makes
no sense if the ASR33 is not even connected to the mains.
I have set both the receive and transmit side of the converter to passive
mode for now (ie they don’t generate the current), but I think the receive
side of the converter will need to be set to be active so that it generates
the current because the drawings of the ASR33 suggest that the ASR33
receive side generates current but the transmit side does not. In fact all the
switches are set to the factory settings at the moment.
I tried switching the receive side of the converter to active and when I
switched on the converter (with the ASR33 disconnected from the mains) the
RD light did not come on this time.
I have also noticed that with the ASR33 disconnected from power the screw
terminal pairs 3&4 and 6&7 appear to be shorted (ie 3 shorted to 4, 6
shorted to 7). I suspect this may be expected but I am not sure.
I have wired screw terminals 3&4 on the ASR33 to the Receiver side of the
Westemo, and 6&7 to the Transmitter side.
I wonder if there is a fault in the ASR33, should it chatter in line mode
when it is not connected to anything?
Which side (if any) of the Westermo should be set to active to generate
current?
Regards
Rob
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