Groups | Search | Server Info | Keyboard shortcuts | Login | Register [http] [https] [nntp] [nntps]

Groups > comp.sys.apple2.programmer > #3104 > unrolled thread

Puzzling the SSC Block

Back to article view | Back to comp.sys.apple2.programmer

Contents

  Puzzling the SSC Block ultramagnus_tcv <mikew@thecomputervalet.com> - 2016-10-09 10:39 -0500
    Re: Puzzling the SSC Block ultramagnus_tcv <mikew@thecomputervalet.com> - 2016-10-09 11:46 -0500
    Re: Puzzling the SSC Block roger.shimada@gmail.com - 2016-10-09 21:18 -0700
      Re: Puzzling the SSC Block ultramagnus_tcv <mikew@thecomputervalet.com> - 2016-10-10 08:16 -0500
        Re: Puzzling the SSC Block Michael J. Mahon <mjmahon@aol.com> - 2016-10-10 12:58 -0500
          Re: Puzzling the SSC Block ultramagnus_tcv <mikew@thecomputervalet.com> - 2016-10-11 18:52 -0500
            Re: Puzzling the SSC Block roger.shimada@gmail.com - 2016-10-11 17:47 -0700
              Re: Puzzling the SSC Block ultramagnus_tcv <mikew@thecomputervalet.com> - 2016-10-12 09:36 -0500
                Re: Puzzling the SSC Block David Schmenk <dschmenk@gmail.com> - 2016-10-12 09:00 -0700
              Re: Puzzling the SSC Block ultramagnus_tcv <mikew@thecomputervalet.com> - 2016-10-12 09:37 -0500
                Re: Puzzling the SSC Block roger.shimada@gmail.com - 2016-10-12 20:37 -0700
                  Re: Puzzling the SSC Block ultramagnus_tcv <mikew@thecomputervalet.com> - 2016-10-13 21:01 -0500
                  Re: Puzzling the SSC Block ultramagnus_tcv <mikew@thecomputervalet.com> - 2016-10-16 08:47 -0500
            Re: Puzzling the SSC Block David Schmidt <schmidtd@my-deja.com> - 2016-10-11 21:27 -0400
              Re: Puzzling the SSC Block ultramagnus_tcv <mikew@thecomputervalet.com> - 2016-10-12 09:31 -0500
                Re: Puzzling the SSC Block David Schmidt <schmidtd@my-deja.com> - 2016-10-12 11:27 -0400
            Re: Puzzling the SSC Block Michael J. Mahon <mjmahon@aol.com> - 2016-10-12 01:18 -0500
              Re: Puzzling the SSC Block ultramagnus_tcv <mikew@thecomputervalet.com> - 2016-10-12 09:39 -0500
      Re: Puzzling the SSC Block ultramagnus_tcv <mikew@thecomputervalet.com> - 2016-10-10 08:26 -0500

#3104 — Puzzling the SSC Block

Hey folks,

Thanks for answering my question about SSC versions. I'm glad to know 
they all work identically.

I'm not adept at reading schematics, but I am trying to puzzle out what 
the block does.

My test rig is an enhanced //e connected to a Raspberry Pi running 
tcpser. I am using ProTERM 3.1 configured for a Hayes SmartMODEM 2400. 
tcpser is running with few parameters, one specifying the baud (2400) 
and another that turns on all debugging statements. I think I 
understand that because there is no modem, there is no DCE. Both 
computers are DTE.

Yesterday during tests to see what works for BBS connectivity and not, 
I found two basic success scenarios.

1. With block pointed toward MODEM, you must introduce a Null adapter 
in-line (or use a Null Modem cable) in order for ProTERM to be able to 
speak to tcpser's modem emulator.

2. With block pointed toward TERMINAL, you can use a straight-through cable.

My understanding of a _basic_ null modem (gathered from here: 
http://digital.ni.com/public.nsf/allkb/1EE0DD8AF67922FA86256F720071DECF) 
is that the TX and RX lines are swapped. For example, with the block 
pointed toward modem and an adapter in-line, TX on the //e side is 
connected to RX on the Pi side.

I figure that since pointing the block at Modem means I have to put a 
Null Modem adapter in-line before the Pi and, in Terminal, I can use 
straight-through, the block must be performing at least some basic null 
adaptation (or connecting RX to TX elsewhere?)

Looking at the schematic (available here: 
ftp://ftp.apple.asimov.net/pub/apple_II/documentation/hardware/schematics/super_serial_card_050-0045-a_schematic.pdf) 
I see the pin-out of the block and the lines on the spot where the 
block is inserted.

I'm not entirely sure how to ask my questions. I am going to try, but I 
may need to ask in different ways.

I think that the image of the block shows the physical pin-out while 
the spot on the schematic shows the pinout of the socket that's most 
convenient for the drawing. In other words, if you were able to 
physically pop-out the block drawing and insert is on the socket space 
in the schematic, pins showing a connection between 1 & 2 in the block 
pin-out wouldn't connect 1 & 15 on the socket.

Is that correct?

If that's correct, then pins on the block drawing showing 1 & 2 
connected would connect Pin 1 of 1489 to CTS.

Is that correct?

If both of those questions mean that I understand what's happening on 
the schematic, then ... what happens when you rotate the block? Where 
the connections inside the block represented in the drawing as it 
exists on the schematic -- 1&2, 3&4, 15&16, 13&14 -- now become 5&6, 
7&8, 12&11, 10&9?

If the block is creating a null adaptation internally (or if this is 
happening elsewhere), where is this happening?

Another question: The block as it is drawn on the schematic is Modem? Terminal?

I realize it might be easier to say, "Lookit, don't worry about it! It 
is what it is," but I would like to understand what's happening if 
possible, even though I'm finding it quite mind-bending.

Cheers,

Mike Whalen 

[toc] | [next] | [standalone]

#3105

Whoops. I didn't noticed I posted this and the other message to 
a2.programmer. Didn't mean to. Wonder if it would be better to post 
csa2.

[toc] | [prev] | [next] | [standalone]

#3108

You are making your brain hurt too much!

The jumper block is described in the Super Serial Card manual, for example at http://www.applelogic.org/files/SCCIIMAN.pdf . The graphic description is described on PDF page 53, the text on PDF page 109.

RS-232 devices are DTE (Data Terminal Equipment) or DCE (Data Communications Equipment). Straight through cables are used to connect them.

Crossover cables are (often) required when connecting computers to other computers or printers.

The SSC jumper block is a neat way to avoid needing a Modem Eliminator (crossover) cable. Sadly the jumper block itself is quite fragile.

And yes, posting to comp.sys.apple2 would have gotten you a faster reply. (I only realized that comp.sys.apple2.programmer was still active after 4AM tweeted it.)

[toc] | [prev] | [next] | [standalone]

#3109

On 2016-10-10 04:18:03 +0000, roger.shimada@gmail.com said:

> You are making your brain hurt too much!


You ain't kidding. :-)

I have puzzled out the main question about the different pins and how 
they map on the socket in different orientations. I have that part down.

But I'd like to know what happens in the SSC to nullify the null modem 
need when pointed toward Terminal.

I'll post that to the proper newsgroup, though. 

[toc] | [prev] | [next] | [standalone]

#3111

ultramagnus_tcv <mikew@thecomputervalet.com> wrote:
> On 2016-10-10 04:18:03 +0000, roger.shimada@gmail.com said:
> 
>> You are making your brain hurt too much!
> 
> 
> You ain't kidding. :-)
> 
> I have puzzled out the main question about the different pins and how 
> they map on the socket in different orientations. I have that part down.
> 
> But I'd like to know what happens in the SSC to nullify the null modem 
> need when pointed toward Terminal.
> 
> I'll post that to the proper newsgroup, though. 
> 
> 

Nothing happens in the SSC, just as nothing happens in the SSC when you
connect to it with a null modem cable. The connector block simply permutes
the cable wires, making a straight-through cable into a null modem and vice
versa. 
-- 
-michael - NadaNet 3.1 and AppleCrate II:  http://michaeljmahon.com

[toc] | [prev] | [next] | [standalone]

#3115

On 2016-10-10 17:58:06 +0000, Michael J. Mahon said:

> Nothing happens in the SSC, just as nothing happens in the SSC when you
> connect to it with a null modem cable. The connector block simply permutes
> the cable wires, making a straight-through cable into a null modem and vice
> versa.

Let me try to state this differently to see if I understand.

Presumption is two DTE devices (SSC and a Raspberry Pi). Since there is 
no DCE (Modem, for example), we need a modem eliminator.

I point the block arrow up toward modem. To communicate with the Pi, I 
have to use a modem eliminator (a null modem cable or adapter) to speak 
to the Pi from the SSC. Inside the modem eliminator, wires are adjusted 
to elminate the need for a modem (e.g. RTS (pin 4 on a 25-pin) is 
connected to CTS (pin 5)). -- 
https://en.wikipedia.org/wiki/Null_modem#/media/File:D25_Null_Modem_Wiring.png 


I point the block down toward terminal. To communicate with the Pi, I 
have to use a straight through cable because, by way of the wires 
inside the block, I have eliminated the need for a modem.

Do I understand?

Thanks!!!

m

[toc] | [prev] | [next] | [standalone]

#3116

On Tuesday, October 11, 2016 at 6:52:01 PM UTC-5, ultramagnus_tcv wrote:
> Do I understand?

Yes.

Hopefully you also have a 3.3V/TTL converter between the SCC and the Raspberry Pi, otherwise you may toast your Pi.

A voltmeter can be used to determine if an RS-232 device is wired as DTE or DCE by measuring TX. TX should normally be negative voltage. (TX goes positive when a one bit is sent.)

Live output lines should have voltage on them. When bi-color LEDs came out they were great to have on RS-232 breakout boxes.

[toc] | [prev] | [next] | [standalone]

#3121

On 2016-10-12 00:47:13 +0000, roger.shimada@gmail.com said:

> Hopefully you also have a 3.3V/TTL converter between the SCC and the 
> Raspberry Pi, otherwise you may toast your Pi.


Hmmm... I don't and I have been using this setup for many months. 
Indeed, ADTPro's website makes no mention of this.

You bring up a good point. What is preventing the Pi from toast?

On the Pi, I am using a USB to serial converter. Perhaps that is 
performing the level shifting?

m

[toc] | [prev] | [next] | [standalone]

#3125

On Wednesday, 12 October 2016 07:36:15 UTC-7, ultramagnus_tcv  wrote:
> On 2016-10-12 00:47:13 +0000, roger.shimada@gmail.com said:
> 
> > Hopefully you also have a 3.3V/TTL converter between the SCC and the 
> > Raspberry Pi, otherwise you may toast your Pi.
> 
> 
> Hmmm... I don't and I have been using this setup for many months. 
> Indeed, ADTPro's website makes no mention of this.
> 
> You bring up a good point. What is preventing the Pi from toast?
> 
> On the Pi, I am using a USB to serial converter. Perhaps that is 
> performing the level shifting?
> 
> m

Yes, that will do all the proper RS-232 levels. The only time you would need to worry about the 3.3V/TTL serial interfacing is if you were connecting to the Pi's GPIO serial port. You're not, so you're good.

Dave...

[toc] | [prev] | [next] | [standalone]

#3122

On 2016-10-12 00:47:13 +0000, roger.shimada@gmail.com said:

> A voltmeter can be used to determine if an RS-232 device is wired as 
> DTE or DCE by measuring TX. TX should normally be negative voltage. (TX 
> goes positive when a one bit is sent.)


Regarding this, TX should normally be negative voltage for DTE? or DCE?

m

[toc] | [prev] | [next] | [standalone]

#3127

On Wednesday, October 12, 2016 at 9:37:47 AM UTC-5, ultramagnus_tcv wrote:
> On 2016-10-12 00:47:13 +0000, Roger Shimada said:
> > A voltmeter can be used to determine if an RS-232 device is wired as 
> > DTE or DCE by measuring TX. TX should normally be negative voltage. (TX 
> > goes positive when a one bit is sent.)
> 
> Regarding this, TX should normally be negative voltage for DTE? or DCE?

My bad, let me be more clear on this.

This assumes that there is nothing connected to the RS-232 port, specifically not to any other device.

A voltmeter will read a negative voltage on TX if the device is wired as a DTE. Zero means that it's an input not output, so measure RD for a voltage. A negative voltage on RD means the device is wired as a DCE.

Voltages on both TX and RD mean:
* Two devices are connected together (possibly correctly)
* Wrong pins are being measured

My concern about the Pi is that I understand that it has 3.3V serial pins whereas RS-232 is going to be using 5V. Since you're using USB, this should not be a problem.

[toc] | [prev] | [next] | [standalone]

#3132

On 2016-10-13 03:37:48 +0000, roger.shimada@gmail.com said:

> My concern about the Pi is that I understand that it has 3.3V serial 
> pins whereas RS-232 is going to be using 5V. Since you're using USB, 
> this should not be a problem.

Yeah, I'm supposing not since nothing smells funny.

I think it would be a problem if I were connecting the Serial 
connection to the onboard pins, though. There's no on-board level 
shifting there, from what I know... 

[toc] | [prev] | [next] | [standalone]

#3134

On 2016-10-13 03:37:48 +0000, roger.shimada@gmail.com said:

> A voltmeter will read a negative voltage on TX if the device is wired 
> as a DTE. Zero means that it's an input not output, so measure RD for a 
> voltage. A negative voltage on RD means the device is wired as a DCE.

Actually, this message comes to me at a good time. I was just trying to 
puzzle out what my RS232 Mini-Tester is telling me with its 
multicolored LEDs (RED/GREEN).

Last night, I tried to do some multimeter probing. My SSC is in 
Terminal mode and I measured the far end of a straight-through cable. 
My ground was on Signal Ground. I don't have a 25-pin breakout board so 
I was using a 9-pin breakout.

Pin 1 (CD) is green and +9 Pin 2 (RD) is red and is -9.

I've read that -3 to -25 is OFF (1) and +3 to +25 is ON (0), then I 
think that green is high and red is low.

Thanks!!!

[toc] | [prev] | [next] | [standalone]

#3117

On 10/11/2016 7:52 PM, ultramagnus_tcv wrote:
> Let me try to state this differently to see if I understand.
>
> Presumption is two DTE devices (SSC and a Raspberry Pi). Since there is
> no DCE (Modem, for example), we need a modem eliminator.
>
> I point the block arrow up toward modem. To communicate with the Pi, I
> have to use a modem eliminator (a null modem cable or adapter) to speak
> to the Pi from the SSC. Inside the modem eliminator, wires are adjusted
> to elminate the need for a modem (e.g. RTS (pin 4 on a 25-pin) is
> connected to CTS (pin 5)). --
> https://en.wikipedia.org/wiki/Null_modem#/media/File:D25_Null_Modem_Wiring.png
>
>
> I point the block down toward terminal. To communicate with the Pi, I
> have to use a straight through cable because, by way of the wires inside
> the block, I have eliminated the need for a modem.
>
> Do I understand?

Gosh, you made this complicated. ;-)  Have you seen this?
http://adtpro.sourceforge.net/connectionsserial.html#Super_Serial_cabling

[toc] | [prev] | [next] | [standalone]

#3120

On 2016-10-12 01:27:50 +0000, David Schmidt said:

> Gosh, you made this complicated. ;-)  Have you seen this?
> http://adtpro.sourceforge.net/connectionsserial.html#Super_Serial_cabling


I did; I know. I am hopeful for a more intimate understanding since I 
am writing that article. However, I don't really _need_ the knowledge. 
Your website and Ivan's Raspple II website explain what to do clearly 
and that is more than adequate.

Parting the curtain just a little bit more, whenever I go into projects 
like this I am haunted by things I don't know or may not know. It's an 
obsession to defend against charges of parroting things I don't 
understand properly. It's a bit silly and overbearing at times... but I 
often can't help myself. This is a prime example.

My mental health bills are yuge.

m

[toc] | [prev] | [next] | [standalone]

#3124

On 10/12/2016 10:31 AM, ultramagnus_tcv wrote:
> On 2016-10-12 01:27:50 +0000, David Schmidt said:
>
>> Gosh, you made this complicated. ;-)  Have you seen this?
>> http://adtpro.sourceforge.net/connectionsserial.html#Super_Serial_cabling
>
> I did; I know. I am hopeful for a more intimate understanding since I am
> writing that article. However, I don't really _need_ the knowledge. Your
> website and Ivan's Raspple II website explain what to do clearly and
> that is more than adequate.
>
> Parting the curtain just a little bit more, whenever I go into projects
> like this I am haunted by things I don't know or may not know. It's an
> obsession to defend against charges of parroting things I don't
> understand properly. It's a bit silly and overbearing at times... but I
> often can't help myself. This is a prime example.

That makes perfect sense, actually.  And there's nothing like teaching a 
thing to learn it yourself.

> My mental health bills are yuge.

:-)

[toc] | [prev] | [next] | [standalone]

#3119

ultramagnus_tcv <mikew@thecomputervalet.com> wrote:
> On 2016-10-10 17:58:06 +0000, Michael J. Mahon said:
> 
>> Nothing happens in the SSC, just as nothing happens in the SSC when you
>> connect to it with a null modem cable. The connector block simply permutes
>> the cable wires, making a straight-through cable into a null modem and vice
>> versa.
> 
> Let me try to state this differently to see if I understand.
> 
> Presumption is two DTE devices (SSC and a Raspberry Pi). Since there is 
> no DCE (Modem, for example), we need a modem eliminator.
> 
> I point the block arrow up toward modem. To communicate with the Pi, I 
> have to use a modem eliminator (a null modem cable or adapter) to speak 
> to the Pi from the SSC. Inside the modem eliminator, wires are adjusted 
> to elminate the need for a modem (e.g. RTS (pin 4 on a 25-pin) is 
> connected to CTS (pin 5)). -- 
> https://en.wikipedia.org/wiki/Null_modem#/media/File:D25_Null_Modem_Wiring.png 
> 
> 
> I point the block down toward terminal. To communicate with the Pi, I 
> have to use a straight through cable because, by way of the wires 
> inside the block, I have eliminated the need for a modem.
> 
> Do I understand?
> 
> Thanks!!!
> 
> m
> 
> 

Yes, you do. 

Although there may be differences between "modem eliminator" cables,
because not all serial port configurations make the same use of the various
handshaking lines. 
-- 
-michael - NadaNet 3.1 and AppleCrate II:  http://michaeljmahon.com

[toc] | [prev] | [next] | [standalone]

#3123

On 2016-10-12 06:18:27 +0000, Michael J. Mahon said:

> Yes, you do.
> 
> Although there may be differences between "modem eliminator" cables,
> because not all serial port configurations make the same use of the various
> handshaking lines.

Yes, I have seen pinouts of many different types.

This page is full of different pinouts for all kinds of serial cables.

http://www.camiresearch.com/Data_Com_Basics/RS232_standard.html

Always nice to talk to you, Michael. Your presence is always calming.

m

[toc] | [prev] | [next] | [standalone]

#3110

On 2016-10-10 04:18:03 +0000, roger.shimada@gmail.com said:

> You are making your brain hurt too much!
> 
> The jumper block is described in the Super Serial Card manual, for 
> example at http://www.applelogic.org/files/SCCIIMAN.pdf . The graphic 
> description is described on PDF page 53, the text on PDF page 109.

On the other hand, those descriptions are very, very helpful, 
especially the graphic. Thank you for pointing that out.

m

[toc] | [prev] | [standalone]

Back to top | Article view | comp.sys.apple2.programmer

csiph-web