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Equipment Discussions >> Mounts

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Jmel
member


Reged: 01/24/12

Loc: Eastern North Carolina
Re: Celestron Nexstar "AUX" port... Serial to TTL new [Re: ur7x]
      #6007250 - 08/05/13 09:11 AM

Wow, that is awesome ur7x! I'm eager to see your posts.

I would really have liked to have incorporated a couple of things into a replacement circuit, if I had the time. One would have been a built in aux splitter, to hook up a gps if one so chose... the other would have been to have incorporated a serial to usb adapter - but on the second point, I realize this may not be as good as it sounds; I understand there are limits not only on the usb length, but also on the length of the cable from the mount to the converter. Serial has the longest length limits.

I was struggling to get both joysticks working. It would have been nice to have a trigger set to shift (not a shoulder button), or to have one stick slew at 9 and the other at a slower slew. I won't be using the joystick much though, it was just fun to play with.


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ur7x
professor emeritus


Reged: 01/08/12

Re: Celestron Nexstar "AUX" port... Serial to TTL new [Re: Jmel]
      #6009904 - 08/06/13 04:56 PM

Regarding "extra" aux port if you are to believe the various CGEM and ASGT wiring diagrams all over the place.

A simple 6 connector RJ11/RJ12 splitter with a jumper over pins 2 and 4 should produce your extra aux port.
http://www.cloudynights.com/ubbthreads/attachments/3870190-Celestron%20HC%20a...

Take care with the jumper since pin 3 is +12V and that will not mix well with the sensitive CMOS level signal on pins 1,2,4 and 6


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Jmel
member


Reged: 01/24/12

Loc: Eastern North Carolina
Re: Celestron Nexstar "AUX" port... Serial to TTL new [Re: ur7x]
      #6011321 - 08/07/13 11:49 AM

I was going to use a surface mount dual rj12 jack from monoprice, but they have some weird color scheme going on, I'll have to number the pins with labels before working with the innards. I was going to mount the box to the head of the cg5 mount, with a 6 inch rj12 flat cable going to it. Then, the converter box would attach to the surface mount 'splitter' leaving another aux port, just in case.


What would be helpful is a pin number to pin number diagram... The 'icons' in that diagram you pasted (which I saw on this thread: http://www.cloudynights.com/ubbthreads/showflat.php/Cat/0/Number/3870386/Main... ) are a little misleading to a non-electronics guy like myself... orientation specifically... I don't want anything to be reversed...

http://www.commandfusion.com/wiki2/_media/rs232_pinout.png

Edited by Jmel (08/07/13 01:38 PM)


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ur7x
professor emeritus


Reged: 01/08/12

Re: Celestron Nexstar "AUX" port... Serial to TTL new [Re: Jmel]
      #6012516 - 08/07/13 10:04 PM

In your pinout link those are the same... The male connector is pictured top down and the female is bottom up... Or in other words... to plug one into the other, one needs to be turned over.

The only wire that should give you pause is the 12V red one... don't screw that one up... the others will not cause damage.

Of course Celestron Pinouts are different then your post. The use a TTL/CMOS signal at the scope, NOT RS232


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Jmel
member


Reged: 01/24/12

Loc: Eastern North Carolina
Re: Celestron Nexstar "AUX" port... Serial to TTL new [Re: ur7x]
      #6018346 - 08/10/13 11:08 PM

I think I'll work on that tomorrow. However, I believe the GPSlim 236 from Holux (which is what I'd use, since I have one currently hooked up to pc and connected to NexGPS) is already outputting TTL...

Here is the manual:

http://www.holux.com/JCore/UploadFile/3205400.pdf

"4.6. Output and Interface
z Output
I. Output protocol
Baud Rate: 38400 bps
Data bit: 8
Parity: No
Stop bit: 1
II. Format. NMEA0183 V2.2: GPGGA (1time/1 sec), GPGSA (1 time/5 sec.),
GPGSV (1time /5 sec.), GPRMC (1time /1 sec.), GPVTG (1 time/1 sec), (GLL,
or SiRF binary format for optional).
III. Datum: WGS84.
z Input/ Output Interface:
I. Compatible Bluetooth Serial Port Profile (SPP), Version1.1 and class 2(up
to 10 meter range).
II. In/Out Port. GPS signal (Out)/Command(In) with CMOS/TTL Level。"

I have the usb to serial cable, which is essentially a prolific serial to usb adapter built into a chip near the usb plug on the computer side:

Table 1
Pin Pin Name Signal and description
1 GND Signal ground, Battery charging ground.
2 VOUT Unregulated voltage out: 3.6 V max 100mA.
3 TXD
Transmit Data. From organizer to peripheral.(Voltage Level is 3.3V ~
5.0V).
4 RXD
Receive Data. Form peripheral to organizer.(Voltage level is 3.3V ~
5.0V).
5 VCHARG
Positive terminal of DC adaptor that powers the internal charging
circuit of Li-Ion battery. The approved power supply is 5.0V +/-
5%@1A.

Edited by Jmel (08/10/13 11:11 PM)


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ur7x
professor emeritus


Reged: 01/08/12

Re: Celestron Nexstar "AUX" port... Serial to TTL new [Re: Jmel]
      #6034948 - 08/19/13 05:03 PM

Understand that two things need to happen here to make this work...

First you need to get the two devices (mount and GPS receiver) to "talk" over the right pinouts at the expected TTL/CMOS levels.

Second you need to get the mount and the peripheral to basically speak the same language.

Celestrons communication protocol is detailed (at least in part) here:

http://www.celestron.com/c3/images/files/downloads/1154108406_nexstarcommprot...


You can see, as you might expect, that there are some rules as to how the mount talks to the hand controller or other attachments... It expects the device to say "Hey, here comes some GPS coordinates" before it sends three (or four) large number sets that denote log, lat, and date/time.

And there is a handshake protocol where the mount after successfully getting the correct information basically says "Thanks, I'm good"

Of course the "Hey, here comes some GPS coordinates" can be as simple as the letter "W" and the "Thanks" can be as simple as "#"

But if this info isn't there it will be like your GPS receiver is speaking German and the mount is speaking Chinese.

I would not just randomly start plugging things into the HC or AUX port unless the manufacture and/or Celestron certifies the device will work.


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Jmel
member


Reged: 01/24/12

Loc: Eastern North Carolina
Re: Celestron Nexstar "AUX" port... Serial to TTL [Re: ur7x]
      #6035228 - 08/19/13 07:20 PM

Agreed... I guess I will continue to use the gps on the pc from here on out. If there was a hardware device that was inexpensive that expected serial output of a gps and could translate to the mount, I'd buy it. But typically these types of devices (if they exist) are not inexpensive.

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ur7x
professor emeritus


Reged: 01/08/12

Re: Celestron Nexstar "AUX" port... Serial to TTL new [Re: Jmel]
      #6130138 - 10/10/13 11:16 PM

Bringing this thread back from the dead....

I have updates...

It took me months but I etched a PC board, bought all of the necessary IC's, Capacitors, cables, connectors, and what not... All of the bits and pieces can be easily sourced for less than $10 if you are willing to wait 20 days of shipping from the far east.

Completed soldering the whole thing today...

I have pictures of all of it that I will happily post and I have PDF's and other formats of my PC board that I will also share...

Also of interest, while I was waiting for parts... a unused #93965 converter came up for sale on flee-bay and I scooped it. It is shipping slower than the second coming, as I watch it track through several USPS sorting facilities on the wrong side of the continent... I suspect I won't have it till after Columbus Day...

My plan is to first get this all working with the #93965...

If it works I may never plug in my home brew version of the #93965... Frankly I'm not all that interested in risking either mount on this circuit... If the #93965 doesn't work I will likely give up and drive it through the HC which I know works.

If it does work... then I will probably build a 12V power connecter/tester to make sure that the voltages are all with in the comfortable range before I risk my mount.

The guys at work, who helped me build this thing are taking an office pool if I will be able to wait to do the necessary testing or if I will just chance it.


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dmdouglass
professor emeritus


Reged: 12/23/07

Loc: Tempe, AZ
Re: Celestron Nexstar "AUX" port... Serial to TTL new [Re: ur7x]
      #6130237 - 10/11/13 12:22 AM

Keep us posted...

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ur7x
professor emeritus


Reged: 01/08/12

Re: Celestron Nexstar "AUX" port... Serial to TTL new [Re: dmdouglass]
      #6147517 - 10/19/13 10:15 PM Attachment (43 downloads)

Update... So my little 93965 arrived... and while it did cross the continent its path seemed as simple and as fast as Hannibal's crossing of the Alps... Be that as it may... the second thing I did when I got this "newish" box home... was take it apart... the first thing was to make sure it works.

So here are what the front of guts look like:


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ur7x
professor emeritus


Reged: 01/08/12

Re: Celestron Nexstar "AUX" port... Serial to TTL new [Re: ur7x]
      #6147537 - 10/19/13 10:25 PM Attachment (37 downloads)

And the back looks likes like this...

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ur7x
professor emeritus


Reged: 01/08/12

Re: Celestron Nexstar "AUX" port... Serial to TTL new [Re: ur7x]
      #6147576 - 10/19/13 10:45 PM

This should solve a lot of the mysteries about the Aux ports and the home built converters...

First off this little OE gizmo's has two IC's and a voltage regulator just like the "home brew" version... and the two IC's are a Max232 and an 74HC125... and the Voltage regulator is a simple 12V-5V regulator... so far so good... interesting that the Home brew has 2 resistors... this one technically has 2 as well... but one is required to support the LED... so really it only has one... And the Home brew has 6 capacitors and this thing has 8! It looks like some of those capacitors might come into play in the Aux split... Maybe they act a form of voltage spike protection that can occur when you plug and unplug things...

And while most of the interesting traces are hidden by the RJ45 and RJ12 connectors... The ones that we can see don't match the Home brew schematic... For example in the photos you can see that pin 9 of the Max232 seems to go to pin 13 of the 74HC125 and yet the wiring diagram has pin 9 going to pins 1 & 4 of the buffer chip... If you follow some of the traces the HC125 chip and at least one of the capacitors is involved in the Aux split... looks like the Aux split is a little more complicated then originally thought too.

With this knowledge in hand.. and after testing that the signal ports on the telescope side of my home built converter weren't outputting more than 5V's I plugged it into my laptop and scope and no surprise... It didn't work... and it didn't do any damage either..

Back to the test of the 93965 with NexRemote...

In short.. Wow.. works fine over a long haul (35') Cat 6 wire... telescope slews, tracks, hibernates and homes with direction from the remote laptop like it was being driven from a hand controller. Mission accomplished... too bad that I couldn't get the home brew to work... The good news is I only wasted about $6 building the thing...

Celestron should consider bringing this back as part of a pier adapter kit for some of their "heavier" mounts.


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ur7x
professor emeritus


Reged: 01/08/12

Re: Celestron Nexstar "AUX" port... Serial to TTL new [Re: ur7x]
      #6154414 - 10/23/13 08:58 PM

Another update.

Not able to leave well enough alone, the two circuits were sent to my radio shop at work to see why one works and one didn't

An employee of mine who understands TTL circuits and IC logic way better than me took a look at both and specifically at the Homebrew circuit... His observation is that the Homebrew should work.

Turns out that as a result of initially installing the 12-5v rectifier backwards I had fried the 74HC125 buffer chip... I swapped that out... and tada... the home brew came to life.

I will post pics and Pdf versions of the PC board tomorrow.

With a little effort this can be made small enough to fit inside of a 2XAA battery box.


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ur7x
professor emeritus


Reged: 01/08/12

Re: Celestron Nexstar "AUX" port... Serial to TTL new [Re: ur7x]
      #6155454 - 10/24/13 12:32 PM Attachment (52 downloads)

So now that I actually have my version of the Home brew working I feel a little more comfortable posting photos.

Here is the PC board in the vice ready to be soldered.


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ur7x
professor emeritus


Reged: 01/08/12

Re: Celestron Nexstar "AUX" port... Serial to TTL new [Re: ur7x]
      #6155465 - 10/24/13 12:36 PM Attachment (75 downloads)

And here is a PDF version of the PC board.

You will see that there are two versions the one in the vice is the smaller one on the right. Since then I moved the 12V rectifier to a more open spot of the board... in version 1.0 it is too jammed up with the buffering capacitors and with its heat sink it is too tall to fit in the 2XAA box that I got on ebay for 99 cents.


In version 2.0 the rectifier has enough room to be bent over and lie flat.

I have tested and can confirm that this circuit works great with both my CGEM and ASGT.

Of course as always... double check your work, and use at your own risk...

If you are following this... on my first attempt I installed the rectifier backwards and was pushing a full 12V through the whole circuit. This fired the 74HC125. Of course if it had of been attached to the scope at the time it would have likely fired something in the scope too...

BEFORE you plug anything like this to your scope, attach it to an external 12V power supply (jumped with the right polarity to the red and yellow RJ12 wires from the scope) and read the volage levels coming back to the scope on the blue, black and green wires... if you see ANYTHING over 5v STOP, and figure out what is wrong.

If anyone wants the native drawing of the PC board or a list of components and cheap ebay vendors to supply them... PM me and I will happily provide them.

I literally bought enough parts to build two of these for about $8.


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derelicte
member


Reged: 08/30/13

Re: Celestron Nexstar "AUX" port... Serial to TTL new [Re: ur7x]
      #6155702 - 10/24/13 02:47 PM

Great work!

Is nextremote the only sw that can communicate with the mount over this interface? The reason I ask is I'd like to build a bluetooth serial adapter that plugs into the aux port and communicates with a tablet running Sky safari.

I have this setup working now, but the bluetooth adapter is plugged into the hand control. I'd like to move it to the aux port so I can power it from the mount and not use another battery.

This circuit is pretty simple. I could design a pcb pretty easily that should only cost a few dollars from my favorite cheap pcb house, oshpark.com

Thanks!


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ur7x
professor emeritus


Reged: 01/08/12

Re: Celestron Nexstar "AUX" port... Serial to TTL new [Re: derelicte]
      #6156320 - 10/24/13 08:40 PM

As far as I have been able to determine, the scope needs either NexRemote or the HC (and not both at the same time) to store the scope alignment... No NexRemote or no HC and the scope is basically clueless as to where it is pointing.

All connections that I have seen that attempt to control the scope need to go through either NexRemote or the HC

There are bluetooth and wifi tools that will let an iPad perform a remote takeover of a PC (or a laptop) but this just add layers of complexity.

Have you tried running the Sky Safari through the virtual com port in NexRemote... That seems to be how it is done.


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derelicte
member


Reged: 08/30/13

Re: Celestron Nexstar "AUX" port... Serial to TTL new [Re: ur7x]
      #6157177 - 10/25/13 10:43 AM

That's a bummer. I was hoping to eliminate the bt connection to the hc.

I haven't tried connecting nexremote to the bt adapter because of a limitation in the nexremote software. It won't let you connect to a serial port above 16. The bt stack running on my laptop creates a virtual com port in the 40's. I haven't bothered to try a different bt adapter and stack to try this out as I don't want to use nextremote as a bridge. I just want the tablet to connect to the scope directly via bt.

So until sky safari can talk to the mount via the aux port, I guess my idea is dead.


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vicd
newbie


Reged: 03/03/13

Re: Celestron Nexstar "AUX" port... Serial to TTL new [Re: ur7x]
      #6244238 - 12/10/13 08:41 AM

First off, congratulations on seeing this undertaking through to the end! Based on this thread it was a wild and challenging ride!

I'm new here and this is my first post. I was hoping you could answer a question though.

I've got Parkinson's disease and the tremors that go along with it so I try to avoid (or at least minimize) soldering tasks. I'd like to try making this homebrew AUX-to-PC port adapter on one of those prototyping boards using sockets, pins, posts, and wire jumpers, etc. rather than soldering and then if/when I get it working I could drizzle it with epoxy to 'lock it down'.

With that in mind, I was wondering... based on what you know now would it be possible or advisable to try to leverage one of the prefab serial to TTL (or USB to TTL) interface modules found on eBay or are they not suitable for the application? Could the right prefab module (maybe one that already includes the 5 V regulator) be wired with the 74HC125 chip to streamline construction?

I saw that this was the root of your original question that kicked off this thread but I didn't see that this possibility got pursued or investigated. Is it worth exploring further?

I wonder why Celestron stopped making the auxiliary port accessory? It was definitely the easiest way to add a PC port to a Celestron mount. It's not like they wouldn't sell!

Thanks in advance for your time.
Vic


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ur7x
professor emeritus


Reged: 01/08/12

Re: Celestron Nexstar "AUX" port... Serial to TTL new [Re: vicd]
      #6244567 - 12/10/13 11:45 AM

Quote:

First off, congratulations on seeing this undertaking through to the end! Based on this thread it was a wild and challenging ride!

I'm new here and this is my first post. I was hoping you could answer a question though.

I've got Parkinson's disease and the tremors that go along with it so I try to avoid (or at least minimize) soldering tasks. I'd like to try making this homebrew AUX-to-PC port adapter on one of those prototyping boards using sockets, pins, posts, and wire jumpers, etc. rather than soldering and then if/when I get it working I could drizzle it with epoxy to 'lock it down'.

With that in mind, I was wondering... based on what you know now would it be possible or advisable to try to leverage one of the prefab serial to TTL (or USB to TTL) interface modules found on eBay or are they not suitable for the application? Could the right prefab module (maybe one that already includes the 5 V regulator) be wired with the 74HC125 chip to streamline construction?

I saw that this was the root of your original question that kicked off this thread but I didn't see that this possibility got pursued or investigated. Is it worth exploring further?

I wonder why Celestron stopped making the auxiliary port accessory? It was definitely the easiest way to add a PC port to a Celestron mount. It's not like they wouldn't sell!

Thanks in advance for your time.
Vic




Thanks for the post, your idea of starting with a prefab serial to ttl board was exactly my idea, but after I got into the project, it became clear to me that the risk to my mount(s) was not worth the few bucks I was going to save so I abandoned that line of thought. To do this I would have to build a test/simulate/stimulate system to ensure that a confortable <5V ttl signal was all that was coming out of the translater. Of course the curiosity here was that I had to build that setup anyway before I was willing to chance a $1200 (or even a $600) mount on a home brew project. And as you will note, as you follow my thread here, it is EASY to make a simple mistake and build something that could (and likely would have) killed my mounts electronics.

I have some luxury in that where I work, I have a small army of guys who work for me who would love to take a break from configuring servers and network equipment and solder something goofy "for the boss".

Ask around,I'm sure you will find friends and family who will solder this up for you in exchange for a bottle of wine or a 6pack of beer.

Failing that, the OE converter still do come up for sale from time to time on the classifieds here or on ebay. They seem to go for about $50 (I got mine for $40), vendor claimed it was "new" It had clearly been out of the box, but it was mint and it works perfectly so who am I to complain.

And ya, given that the guts of these things probably cost Celestron around $1.50 (I bought enough components to build 2 for less than $8...) I can not see why the new mounts don't come with PC ports built in or even better why they don't still sell these converters.

Once you have controlled your mount with a PC app like TheSky (or what have you), you will never got back to the hand controller. For those of us with a semi-permanent pier set up, or a permanent observatory, this is the first thing to buy/build/obtain.


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