Jump to content

Stargazers Lounge Uses Cookies

Like most websites, SGL uses cookies in order to deliver a secure, personalised service, to provide social media functions and to analyse our traffic. Continued use of SGL indicates your acceptance of our cookie policy.

sgl_imaging_challenge_banner_dslr_mirrorlesss_winners.thumb.jpg.9deb4a8db27e7485a7bb99d98667c94e.jpg

Alaness

Why are new mounts still coming with serial cables?

Recommended Posts

It's something that really confuses me. My HEQ5 pro has come with only a serial cable to connect the mount to a PC. Serial ports haven't been used for over 10 years now. It's disappointing that I have to go out and buy a USB adapter as if I'm trying to use some ancient hardware. It can'be be that hard for them to upgrade the mounts to include a simple USB port can it?

Share this post


Link to post
Share on other sites

I'm sure it wouldn't be that hard, no. But where's the motivation? Whilst people can still go out and buy a USB<->RS232 converter if they want to connect the mount to a PC (which many users may not ever do) I don't imagine they'll bother.

Lots of non-consumer grade hardware does still use RS232, or perhaps RS423 these days. Personally I reckon it would all be much easier if everyone used ethernet instead :)

James

Share this post


Link to post
Share on other sites

I'm glad they don't otherwise my LXD couldn't be run by my HP Laptop (or is that Lapblock) running Windows 98. Why do I use that old HP thing........ I don't have a observatory as such and as it gets warm it seems to do ok when damp. Not the sort of conditions for a nice shiny new laptop with usb ports!!

But I do know where you are coming from.

Clear Skies

Share this post


Link to post
Share on other sites

The serial port doesn't take standard voltages - don't hook it up directly. You need an EQDIR adapter (or a special USB-serial cable with the adapter built in).

Share this post


Link to post
Share on other sites

Ps - the supplied cable (and instructions regarding USB) is to connect a PC to the handset, not to the mount.

The mount takes 5V TTL signalling and you need a big boxy EQDIR module, an FTDI TTL232R cable plus a bit of work, or see Shoestring for a ready built cable.

Also - look at EQTOOTH for a Bluetooth wireless option.

Share this post


Link to post
Share on other sites

RS232 (serial) is still the standard connection for professional engineering.

USB only replaced serial for consumers electronics products.

I am sure you know about the Murphy's law - Anything that can go wrong will go wrong.

There is a lot less to go wrong with a serial port than a USB. Furthermore, USB has a max cable length of 5m, which is a bit short if you want to control your mount from inside your house. In comparison, RS232 can do 15m with a standard cable and excess of 300m with low capacitance cable, which makes it a much more sensible choice for mount control.

Vixen updated their GOTO from RS232 to a modern IP based Ethernet connection in the Starbook. You may think it's a sensible option, every computer has Ethernet port and CAT5 cables can run up to 100m, but everyone hated it. The protocol is harder to understand and much less user friendly than serial.

Share this post


Link to post
Share on other sites

Vixen updated their GOTO from RS232 to a modern IP based Ethernet connection in the Starbook. You may think it's a sensible option, every computer has Ethernet port and CAT5 cables can run up to 100m, but everyone hated it. The protocol is harder to understand and much less user friendly than serial.

I really don't understand why that had to be. In terms of the way the OS presents the connection to the application there need be no real difference whatsoever in protocols and in fact if you look back at UNIX systems before and after ethernet became common, many of the protocols used for communication (eg. email) remained exactly the same.

Granted if you're building an embedded system to control the mount it's much more tricky, but these days some of those are layered on top of some sort of microkernel that does much of that work for you.

James

Share this post


Link to post
Share on other sites

USB sockets and connectors are quite flimsy and easily broken, the connections made between the plug and socket pins are often poor too.

  • Like 1

Share this post


Link to post
Share on other sites

You get the same problem with after market car ECUs only now are some of the manufacturers moving over to USB. I guess they stick with it to keep their costs down and because it moves all the data it is required to. But it certainly is a pain for connecting modern PC kit to.

Sent from my Nexus 7 using Tapatalk 2

Share this post


Link to post
Share on other sites

The reason is simple: if it ain't broke don't fix it. Serial is about the simplest protocol possible, a standard UART and job done.

Sent from my iPhone using Tapatalk

Share this post


Link to post
Share on other sites

Another thing I like about serial connectors is that they usually have some sort of retaining screw. I always feel a bit nervous with USB connectors because there seems to be so little holding them in place.

James

Share this post


Link to post
Share on other sites

Another thing I like about serial connectors is that they usually have some sort of retaining screw. I always feel a bit nervous with USB connectors because there seems to be so little holding them in place.

Tell me about it!

Lost count how many times USB plugs have come out for one reason or another.

This is what should have been done ...

http://www.usbgear.com/computer_cable_details.cfm?sku=SC-U2MAB&cats=102&catid=187%2C102%2C188

SC-U2MAB11.jpg

Edited by Cath

Share this post


Link to post
Share on other sites

Personally I reckon it would all be much easier if everyone used ethernet instead :)

Can but hope!

Most people have wireless lan these days, the handset/mounts ort to have wireless modules built in these days.

Share this post


Link to post
Share on other sites

Tell me about it!

Lost count how many times USB plugs have come out for one reason or another.

Especially when a lot of USB devices uses the tiny Mini-B or Micro-B connector rather than the larger and more robust Type-B at the accessories end.

However, the USB type connection does have one advantage. It will pop out when you trip over it. If the RS232 port wasn't design properly and the connector was only secured to the PCB rather than to the chassis (like the one on Starbook S) then you risk ripping the whole thing from the PCB if you tripped over the cable.

Share this post


Link to post
Share on other sites

However, the USB type connection does have one advantage. It will pop out when you trip over it. If the RS232 port wasn't design properly and the connector was only secured to the PCB rather than to the chassis (like the one on Starbook S) then you risk ripping the whole thing from the PCB if you tripped over the cable.

There is that, although best to try and make sure you cover/route the cables so you can't trip over them anyway.

USB cables can still give a nice big tug on something if you happen to trip over the cable and pull it to one side of the USB connection rather than straight out, or so I found :rolleyes2:

Share this post


Link to post
Share on other sites

There is that, although best to try and make sure you cover/route the cables so you can't trip over them anyway.

USB cables can still give a nice big tug on something if you happen to trip over the cable and pull it to one side of the USB connection rather than straight out, or so I found :rolleyes2:

True, I broke two USB headset doing just that. Fortunately it didn't damage the USB port in the computer.

Share this post


Link to post
Share on other sites

Ethernet. Period.

I simply cannot understand why an RS232 connection should be used at all. Has anyone eyeballed the original specification for EIA RS-232? I recall the maximum communication distance is ten feet or so. Of course it will go longer, but a non-differential transmission method is very sensitive to interference and shouldn't be used. That is probably why the marine and industrial worlds have opted for RS-422 and RS-485.

So, you connect your mount to a PC via 2400 bps RS-232. One start bit, one stop bit, ten bits per byte. Or a whopping 240 characters per second! Yeah! Send a set time command to your mount (let's assume LX communication) and you need a good 100ms just to get the data over to the mount. Poll it for Ra and Dec five times a second and the serial line is at half capacity and your application is slowing down.

No, I stay away from serial ports.

As for the protocol... I have written a full ASCOM driver for the GM-series of mounts from 10Micron. The whole ASCOM initiative is a .NET environment and as such it provides exactly (exactly) the same API:s for serial ports and TCP connections. So, is it harder to handle TCP compared to RS-232? Nope. It just ain't ;)

So I say KILL THE SERIAL PORTS NOW! Just leave one for a standard NMEA 0183 GPS...

/per

Edited by perfrej
  • Like 2

Share this post


Link to post
Share on other sites

To be fair, I regularly used to use serial connections at far faster rates than that in electrically noisy environments without any problems. But let's not worry about that because fundamentally I agree with you :) Ethernet is cheap, easy, ubiquitous, reliable and allows multiple high speed connections to be multiplexed over tens of metres down a single cable (or several, if you need the bandwidth). What's not to like?

Just don't let someone at the mount manufacturers say "You know, I've got a load of this thicknet stuff and vampire taps..."

James

Share this post


Link to post
Share on other sites

If you really don't want the cable ... http://www.usconverters.com/index.php?main_page=product_info&cPath=70&products_id=404 ... yes, Radio Shack part number 232 dragged kicking and screaming into modern times. Not only connects to your own telescope, but those of all your neighbours - and with the optional "ASTROSNORT SUPER SIGNAL BOOSTER" ($12,000,000) and HUBBLEHACK mod you can greatly improve your viewing experience.

People who bought this item also bought:

  • 25 Megatonne thermonuclear cloud dispeller (single use only - no refunds, adult supervision advised)
  • "Turn Right at Orion" - southern hemisphere version of the popular book
  • Norton's Virus Atlas - electronic version, filters out all spam from alien civilisations
  • Counter-Rotating Earth Mass Black Hole - solve tracking errors once and forever (shipping charges apply)
  • Like 2

Share this post


Link to post
Share on other sites

Part of my day job involves connecting PCs to electron microscopes. By far the most reliable connection method is RS232. Better than Ethernet or some sort of DCOM over a network. With those you are in a world of incompatibility and fighting your way past modern security on networks and PCs.

I had three days in Marseilles last week helping to get connection to a TEM working.

RS232 is not fast or modern but works, and when it doesn't it's easy to find out why.

Share this post


Link to post
Share on other sites

Ah, but do not confuse a naked TCP with DCOM or the likes. TCP is just as simple as RS232. DCOM lives a couple of steps up the OSI ladder and is plagued by a couple of annyoing, albeit simple, problems that a lot of people have a problem understanding. I have spent years with DCOM ;)

/per

Share this post


Link to post
Share on other sites

I'm not confusing naked TCP/IP with DCOM, some systems use that. It's next in ease to implement after RS232. If you already have it or need the speed then fine but for something simple like a mount, focuser, filter wheel or rotator Ethernet is far more complex and expensive. For a camera I'd go for Ethernet over USB.

Share this post


Link to post
Share on other sites

The thing is that a mount is not as simple as it seems. There is a lot of data flowing. Let's take an example. I use the following software packages at the same time:

  • CCD Autopilot
  • FocusMax
  • MaximDL
  • Model Maker
  • Cartes du Ciel

All of them poll the mount for position information and capabilities. The frequency of polls varies from once a second to five times per second. If I used a serial connection for that I would have two problems: more than one client and speed.

This is not a problem if you're doing visual and just need a planetarium program running, but with all that stuff running the serial port becomes the narrowest part of the chain.

USB is fine were it not for the connectors. mechanically they're as bad as can be.

/per

Share this post


Link to post
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.


  • Recently Browsing   0 members

    No registered users viewing this page.

×
×
  • Create New...

Important Information

By using this site, you agree to our Terms of Use.