[GreenKeys] TTY-CONNECT circuit board

[gil smith]

Hi folks:

You have probably been wondering what ever happened to the TTY-CONNECT 
circuit board I started some time ago.  I have been busy as usual, but I 
managed to steal some time over the holidays.  I just put the finishing 
touches on the board, and sent it off for a few protos.  You can see what 
it looks like:

http://www.vauxelectronics.com/gil/tty-connect/091-0714-A-assy-wide.pdf

As I have more available on this project, I will add the files to:

http://www.vauxelectronics.com/gil/tty-connect/

I have also acquired the domain baudot.net, and hope to get my tty stuff 
set up under that -- I'll let you know when that happens.

I'll provide more info after I get a proto together.  I then need to spend 
some time with the software.  While the board will be handy without the 
optional micro, it should be quite flexible with the features the micro can 
provide.


A brief description of TTY-CONNECT:
-----------------------------
This second-generation design provides everything needed for connecting 
most teletype machines in up to three local current loops, and for 
connecting a computer (PC) and/or a radio terminal-unit (TU) via RS-232 
serial ports.  Power is provided for the TTY loops (and current-limiting), 
as well as full opto-isolation.  Note: this unit is NOT designed to connect 
to externally-powered loops.

You can use the unit simply as a loop supply for connecting multiple TTYs 
on a loop.  Or, you can patch a loop to a computer's 232-serial (com) port, 
allowing a program on the computer to talk to the tty gear.  Or, you can 
patch a loop to a radio terminal-unit's 232-serial port, and have the tty 
gear print the received rtty broadcast.  Or, you can include the optional 
microcontroller to provide loop routing, and automatic features like 
ascii/baudot conversion, speed conversion, CR-LF insertion, etc.

The board is 9.6 x 2.9 inches, and the parts fit easily into a 2U rack 
chassis that is 7" deep, or into a metal box of about 12 x 7 x 3 minimum.

Features (you may need to widen your window to read this properly):

1)  HV1 -- High-Voltage TTY Loop 1:
     This loop has a 150V loop supply, 60-mA (or 20-mA) current limiting, 
two insulated
     1/4" jacks for TTYs (M14, M15, M19, M28...), and full opto-isolation 
for data in and out.
     A switch configures the two jacks for full- or half-duplex mode.  In 
full-duplex mode,
     one jack is an input loop (HV1-IN, for keyboard/td-contacts) and the 
other jack is an
     output loop (HV1-OUT, for typing-unit/reperf selector magnets).  In 
half-duplex mode, the
     jacks are connected in series for a local loop of keyboard/td-contacts 
and/or selector
     magnets.

2)  HV2 -- High-Voltage TTY Loop 2:
     This second HV loop is identical to HV1.

3)  LV -- Low-Voltage TTY Loop:
     This loop has a 22V loop supply, 20-mA current limiting, two insulated 
3.5mm (1/8") jacks
     for TTYs (M32, M33...), and full opto-isolation.  The 3.5mm jacks are 
not standard,
     but are small and convenient, and prevent inadvertent connection to a 
150V loop (units
     like the M32/33 are only rated to 120V, and high-voltage is not needed 
as with older gear).
     A switch configures the two jacks for full- or half-duplex mode.  In 
full-duplex mode,
     one jack is an input loop (LV-IN, for keyboard/td-contacts) and the 
other jack is an
     output loop (LV-OUT, for selector magnets).  In half-duplex mode, the
     jacks are connected in series for a local loop of keyboard/td-contacts 
and/or selector
     magnets.  Note: this unit is NOT designed to connect to an 
externally-powered loop.

4)  TU-232 -- an RS-232 interface for connecting to a Radio/Terminal-Unit:
     A 6P6C modular jack allows connection of a TU for receive and/or 
transmit use.
     The signals are available for either driving an optional on-board 
microcontroller,
     or for patching directly to one of the opto-isolated TTY loops.
     If the TU-232 port is patched directly to a loop, the TTYs must be 
able to receive the
     correct word format received by the radio/TU (eg: 75-wpm baudot).
     This interface is for standard RS-232 signals (mark < -3V, space > 
+3V).  If the optional
     PIC microcontroller is installed, there is a software inversion 
available for connecting to
     a TU with MIL-188 signals (mark = +5V, space = -5V).

     If the optional PIC micro is installed, there is also a push-to-talk (PTT)
     signal available on the TU-232 jack -- this is an open-collector 
transistor
     (not opto-isolated), for keying a transmitter.  When the micro drives 
this line active,
     the transistor will pull to ground and sink up to 100 mA (40V 
max).  If you are driving
     a relay (or other inductive load), be sure to add a freewheel diode 
across the coil
     (anode to collector, cathode to v+) to protect the transistor from the 
di/dt spike.

     For connection to the Tempest Dovetrons, a special cable with a couple 
of BNC
     plugs and a 6P6C modular plug will be needed, to connect to the 
dovetron's POLAR (232 in)
     and OUTPUT (232 out) jacks.  Or, you could tap into these points 
internally, and just
     bring a 6P6C cable out the back of the dovetron.

5)  PC-232 -- an RS-232 interface for connecting to a PC:
     A DB9-F jack allows a PC to connect using a standard straight 9-pin 
male-female cable.
     The signals are available for either driving an optional on-board 
microcontroller,
     or for patching directly to one of the opto-isolated TTY loops.  If 
the PC-232 port
     is patched directly to a loop, the PC program must be able to send the 
correct word
     format required by the TTYs (eg: 60-wpm baudot).

     The DTR and RTS signals on the PC-232 jack are buffered and available 
on the AUX jack,
     an 8P8C modular connector.  These buffered outputs may be used for 
radio keying, or other
     functions;  the PC program can then control the state of these lines 
as needed.
     These lines drive open-collector transistors (not 
opto-isolated).  When the RTS or DTR
     line is active (positive) the associated transistor will pull to 
ground and sink up to
     100 mA (40V max).  If you are driving a relay (or other inductive 
load), be sure to add
     a freewheel diode across the coil (anode to collector, cathode to v+) 
to protect the
     transistor from the di/dt spike.

6)  Optional PIC microcontroller:
     This micro may be used to provide signal routing between the loops, 
TU, and PC,
     ascii-to-baudot conversion, baud-rate conversion, auto-line-feed 
insertion, detection
     of command sequences, motor control, digital i/o...
     There is also a memory (eeprom) socket, used for buffering during 
high-to-low-speed
     conversions.  If the PIC is not installed, fixed patching of the 
TU-232 and PC-232 ports
     directly to the tty loops may be performed at the J4 (INTERCONNCT) header.

7)  Optional Motor Control:
     A future accessory board will connect to connector J10 (EXP-1/MOT) and 
provide relay
     switching for TTY motors.  The PIC micro will switch TTY motors on/off 
automatically...

8)  Optional LCD display:
     An LCD display/keypad from Matrix Orbital connects to the PIC at 
connector J11 (EXP-2/LCD).

Not all of the circuitry needs to be installed.  The board is flexible, so 
you can build it
the way you need it.  Build only the sections you need:  HV1, HV2, LV, 
TU-232/PC-232, and/or
the microcontroller.


Changes from original TTY232 board (circa 2000):
-------------------------------
- new form factor to put all connectors on rear
- soldermask and silk this time
- Simplified loop interface circuitry a bit.
- HV loop RC snubber interfered with the loop sense, and had to be
    disconnected in half-duplex -- using diode clamp now -- simple and clean.
- Added second (optional) HV loop.
- Lowered voltage on LV loop.
- Added duplex switch to LV loop (was half-dup only).
- got rid of the rs-485 and X10 ports.
- added second 232 port for TU, and PTT output
- added buffered DTR and RTS outputs
- added expansion ports for motor control and lcd
- all 232 and opto-isolated loop signals are available at 20-pin header
    for loop/232 patching (if micro not used) or cabling to other location.

later,

gil



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