[GreenKeys] Current Loop to RS-232 Conversion on ASR33
Christian Gauger-Cosgrove
captainkirk359 at gmail.com
Tue Mar 19 09:58:38 EDT 2013
Ah, well my usual experience is DEC minicomputers, they preferred full
duplex connections. Mostly because full duplex also didn't echo control
codes back to the teletype if it didn't need them, and the whole password
security thing that happened to become prevalent later on.
You mention the HP2000; I have no idea about how Hewlett-Packard did
things, but I am well versed in DEC.
Cheers,
Christian
On 18 March 2013 23:08, <COURYHOUSE at aol.com> wrote:
> **
> 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> 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<alf_fisher at tiscali.co.uk>
>> ]
>> *Sent:* 24 February 2013 21:39
>> *To:* r.jarratt at computer.org; 'Teletypeparts'; 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 <robert.jarratt at ntlworld.com>****
>> *To:* r.jarratt at computer.org ; 'Teletypeparts' <teletypeparts at aol.com> ;
>> 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<greenkeys-bounces at mailman.qth.net>
>> ] *On Behalf Of *Rob Jarratt
>> *Sent:* 10 February 2013 23:10
>> *To:* 'Teletypeparts'; 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<teletypeparts at aol.com>
>> ]
>> *Sent:* 10 February 2013 22:28
>> *To:* r.jarratt at computer.org; 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>
>> To: 'Teletypeparts' <teletypeparts at aol.com>; greenkeys <
>> 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<greenkeys-bounces at mailman.qth.net?>
>> ] *On Behalf Of *Teletypeparts
>> *Sent:* 10 February 2013 18:20
>> *To:* r.jarratt at computer.org; 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>
>> To: 'Teletypeparts' <teletypeparts at aol.com>; greenkeys <
>> 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<teletypeparts at aol.com?>
>> ]
>> *Sent:* 09 February 2013 20:30
>> *To:* r.jarratt at computer.org; 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>
>> To: greenkeys <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), 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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