[GreenKeys] New Loop Converter Prelim specs

Wed, 26 Feb 2003 13:25:53 -0500

I think we'll start calling you 'Saint Gil"...  My gracious.  you couldn't
ask for more.

Let us know how much.  You've saved me a lot of work, and my result was
gonna be just a loop interface, and nothing more.

Thanks,
(the other) Gil

----- Original Message -----
From: "gil smith" <[email protected]>
To: <[email protected]>
Sent: Wednesday, February 26, 2003 1:14 PM
Subject: Re: [GreenKeys] New Loop Converter Prelim specs

> Hi folks:
>
> Thanks to all who responded with feature requests -- I hope I have them
all
> covered here.  This interface is sounding a lot like the one I did a
couple
> of years ago.  Many of you got these boards, and a few of you even built
> them up:
>
> http://www.vauxelectronics.com/gil/tty232/tty232/
>
> I think all we need is a second-generation of this board;  some thoughts:
> I will get rid of full-duplex, since it seems to be rarely used and it
will
> simplify things.  I will get rid of the rs-485 and X10 ports.  I want to
> try a constant-current HV loop to replace the big-frickin'-resistors
(maybe
> a TO-3 on a heatsink).  I need to investigate the snubber, since it
> interfered with the loop sense, and had to be disconnected in half-duplex.
> I will keep the optional low-voltage loop, since even though no one here
> needs it, there are applications for hanging a 33 onto a computer with
> speed conversion (I have such an application, so it stays).  I can use up
> to maybe 200 bytes of internal pic memory for speed-conversion buffering,
> but I want to investigate adding an sram chip -- adding a 32K, 128K, or
> 512K chip should handle your buffering needs, I would think.  Jack tells
me
> the speed-converting versions of dovetrons used 200-char fifos, so the
sram
> may only be needed for streaming text.
>
> So some prelim specs:
>
>
> 1)  External box with loop supply transformer, DB-9 232 connector, loop
> jacks...  But it could still mount inside a dovetron if desired, and take
> advantage of the HV winding and power supply voltages.  Otherwise a
special
> cable with a couple of BNC plugs and a DB-9 will be needed to connect to
> the dovetron's POLAR (232 in) and OUTPUT (232 out) jacks.  Or a straight
> DB-9 cable to connect to a PC.  I might just put a DB-9 on my dovetron to
> make cabling easy.
>
> 2)  High-Voltage (120-150V), 60- or 20-mA loop, and four insulated 1/4"
> jacks for one to four TTYs (M15, M28...).  Half-duplex only.
>
> 3)  Low-Voltage (30V), 20-mA loop, and one insulated 3.5mm jack (M32,
M33...).
> Half-duplex only.
>
> 4)  RS-232 interface using fully opto-isolated connections to either HV or
> LV loops.
>
> 5)  Optional PIC microcontroller -- provides configurable options such as:
> baud-rate conversion, ascii-to-baudot conversion, auto-CR-CR-LF-LTRS at N
> chars (default 72), auto-line-feed insertion after CR, etc.  If PIC is not
> installed, jumpers connect the 232 port directly to the tty loop
interface.
>
> I did the baud-rate conversion and ascii-to-baudot conversion code already
> on the TTY232 pic, but it only had a small internal pic buffer, and relied
> on serial port xon/xoff flow control to throttle data.  Flow control is
not
> an option on a TU, so need to add ram chip as well.  The code for the
> TTY232 pic was ascii-only input, and baudot or ascii out.  I need to
> provide for baudot input as well.
>
> 6)  Auto-power the TTY, by detect incoming data, buffering it, turn on a
> TTY motor relay, delay for spin-up, then let data flow.  Some sort of
> SelCal is possible here as well, if you help me define a string to watch
> for (programmable, but perhaps default of ZCZC).  Shutdown string would be
> handy too (perhaps default of NNNN).  Input appreciated.
>
> 7)  A char counter might be more work than it is worth, but I could likely
> activate a signal line at N chars (default 70).  This could be used for a
> bell, or could activate a light until CR entered.  Let me know what might
> be handy.
>
> 8)  Store and replay test messages?  Answerback string?  Lots of
> possibilities for stuff stored in eeprom.
>
> 9)  Provision for an externally-powered loop, instead of an internal loop
> supply?  Let me know.
>
> 10)  Commonly-available parts, of course.  Bare-boards, or full kits will
> be available.
>
>
> thanks,
>
> gil
>
>
>
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