AUTOSTAR INFORMATION Last updated: 19 January 2004

Autostar #494 and #506 Cable Information

Date: 1/16/04, 05:31
From: Signal20FHP@aol.com
re: cable for pc to scope I think the modular jack is on the scope not
on the handset. In that case which way is the correct orientation foe
Pin 1. and i assume that the pinout is read from the jack back not the
front
please advise
george in Miami Fl

And:

I think I found the info on the 506 cable
the the 70 scope uses a different protacal not rs232 and the cabe is
just not a cable but a electronic circuit to chage the info
I am I correct in my info

And:

From: Richard Seymour (rseymour@wolfenet.com)
He has an ETX70... which requires a must-be-bought-from-Meade
506 cable/converter unit.

You do NOT connect the PC serial port directly to an AUX socket
on the telescope base.

(if you had an Autostar 495 or 497, with the serial socket IN THE
AUTOSTAR, then you -could- home-build a 505-type cable,
as shown on Mike's site).  But with a no-numeric-keypad 494
Autostar, you -must- BUY the cable (or a different Autostar,
which is my usual recommendation)

have fun (but don't smoke your scope)
--dick

On the off-chance that you really DO want the AUX pinout,
-all- of the ETX/Autostar/LX90 sockets are portrayed here:

http://jan.eaglecreekobservatory.org/pinouts.html

have fun
--dick

The I2c serial bus is a bi-directional 2 wire inter IC communication
link between IC circuits.

it has 3 speeds Standard,High and Fast and is what is used in the 506
cable It operates under dofferent voltages and  it more then likley has
a Zeiner voltage regulator diode and a resistor in the DB -9 plug end of
the cable to lower the voltage to the I/O board in the base of the
scope. The 497 Handbox more then likeley has it built into it as the PC
plugs into the Handbox and not directley into the base of the scope as
it does when you use the 494 handbox

If you can find out the voltage needed from the pc to the i/o board in
the base of the scope you will be able to clone the cable.I bet if you
open the DB-9 plug the diode and resistor are inside.

the reason that the pc board gets cooked is that you are putting 9 volts
that runs the scope into the I/O  and it may need only 3 volts

George in Miami

From: Richard Seymour (rseymour@wolfenet.com)
Your guesses (bets?) about the 506 cable/converter would be a
nice theory... but are very close to totally inaccurate.
You also do not account at all for the bipolar operation
of rs232 signalling.  Nor for the full-duplex nature of
the I2C data lines somehow being turned into the two
half-duplex wiring system of rs232 communications.

> The I2c serial bus is a bi-directional 2 wire inter IC
> communication link between IC circuits.
> it has 3 speeds Standard,High and Fast and is what is
> used in the 506 cable
> It operates under dofferent voltages and  it more then
> likley has a Zeiner voltage regulator diode and a resistor
> in the DB -9 plug end of the cable to lower the voltage
> to the I/O board in the base of the scope.

You missed many critical aspects (especially in Autostar usage):
The I2C bus is an -addressed- bus.. and allows -multiple-
devices to be connected to it. 
Meade does -not- simply change the rs232 voltages (which
drop below zero as well as rise above) and use the AUX
connector as a serial port dedicated to -only- the 506.
You can have focusers and other devices plugged into the
AUX sockets -with- the 506, and each operates without
confusing the other.

Visit:
24.237.160.4/files/astronomy/Autostar/506_cable/

for a photograph of the insides of the 506. Image
24.237.160.4/files/astronomy/Autostar/506_cable/05040005.jpg
(AUX cable comes in on the left, rs232 cable on the right)

shows everything... see the AT89C1051 ? 
That's an 8-bit microprocessor. 
It "intelligently" communicates with the Autostar, and that
89C1051 then performs all of the rs232 operations.

I agree that one -could- (possibly) create merely a
voltage level shifter (which the "232C8N" chip is, mostly),
but the Autostar's programming does not deal with the 506 in
that fashion... it sends an address to inform the 89C1051 to
"listen" or "speak", and then sends (or waits for) data.
But it depends upon the 89C1051 to do the 9600 baud to
(roughly) 100 kbaud speed elevation for the shared AUX bus
usage  (in the 497 Autostar, the AUX bus is an independent
pair of wires... in the 494 Autostar, the AUX data line is
-shared- with the motor circuits.. so it cannot be tied up
by the slow transitions of a "resistor-converted" rs232 signal.

> The 497 Handbox more then likeley has it built into
> it as the PC plugs into the Handbox and not directley
> into the base of the scope as it does when you use the 494 handbox

The 497 (photo at
http://www.weasner.com/etx/autostar/as_schematic.html ) uses a 232
level converter (similar to the 232C8N in the 506), but that is
then fed to the on-chip serial port (UART) in the mc68hc11 processor.
As it happens, that same UART -is- connected to the AUX cabling
in the 494... but the =programming= does not use it, so that fact
cannot be used to operate a normally-programmed 494 Autostar.

> If you can find out the voltage needed from the pc to the
> i/o board in the base of the scope you will be able to
> clone the cable.

If it were true, you could, and there would be articles on Mike's
site about it.

> I bet if you open the DB-9 plug the diode and resistor are inside.

See above photo.  (memo: don't bet on things that are easily disproved)

> the reason that the pc board gets cooked is that you are
> putting 9 volts that runs the scope into the I/O  and it
> may need only 3 volts

The reason things get cooked is that rs232 levels range from
negative 12 volts to positive 12 volts... which (if fed into
the AUX port) destroy the AUX port drivers... which (in the 494)
means you have destroyed the motor data drivers.
Merely resistor-lowering the "12v" to "3v" (and you need a
-series- diode as well, to block the negative voltages) will
merely interfere with motor operation.

Please do more reading on the functioning of the I2C **BUS**
It is not just a simple "data only" cable like rs232.
For that matter, rs232 has -two- unidirectional wires
(send and receive), but I2C only has -one- (and a clocking line).
So (if it were merely resistor/diodes) which of the rs232 wires
do you connect to that  bidirectional line?  Both?  Then you
would be looping the PC's data stream right back to the PC..
(and would not be providing the negative voltages -required-
by the PC to be -seen- as "rs232" signals.

I have always said that making a 506 is -difficult- (not impossible),
since one -could- analyze the I2C signals and program an I2C
device to perform the same activities:
(a) recognize my address, accept a data byte to send as rs232;
(b) recognize a different address, send the last-received rs232
byte to the Autostar;
(c) recognize a -third- address, and supply a "status" word
to the Autostar  (character available, data overrun, etc.)
(there may be a (d),(e) and (f))

So that's "simple", but would involve far more effort than a
506 is worth.

have fun
--dick

And more:

Thanks Mike for the info from both yourself and Dick.

But one more question.

If all of this info on the 506 is being discussed.why has no one ever
taken a 506 cable apart and find out what is has inside of it and build
there own Is this cable sealed in a potted material or has no one every
tried

George in Miami

And this:

From: Richard Seymour (rseymour@wolfenet.com)
As Mike said, this:
24.237.160.4/files/astronomy/Autostar/506_cable/05040005.jpg
is a very detailled photo of the inner components.

All components are easily identified (the oblong is the crystal)

have fun (but follow the links)
--dick

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