Shoestring Astronomy USB vs Parallel for HEQ5 Pro

[glasseyes (John)]

Hi all,
I have read a few posts regarding autoguiding with a webcam and I notice that a lot of you out there are using the Shoestring USB interface ($66) rather than the Parallel ($35) interface. Is there any reason why the USB is a better way to go?
My laptop has a DB25 parallel port and a DB9 serial port as well as USB1 & 2.
Can I use the software upgrade cable supplied with my HEQ5 Pro (DB9 serial -> RJ12) to guide my HEQ5 Pro via the handset RJ12 jack, or is the slower data transfer rate gonna cause probs ?
Thanks in advance.

[ballaratdragons (Ken)]

My only motive for using the USB is because I need the parallel port for my Toucam's long exposure lead, as it plugs into the parallel port.

[glasseyes (John)]

OK thanks Ken. I thought that the parallel version had all the pins extended out at the back so that you could piggy back another parallel plug behind it for extra functions?
I guess that could get a bit messy though?

[ballaratdragons (Ken)]

I enquired about that one too, but Darren (wombat) explained the good and bad of the different connections. USB is the way to go, even if you don't use the Parallel port for anything else.

I don't understand why, but I trust Darrens Computer Technician experience.

[rsbfoto]

Hi,

I do guide with the parallel port and before that direcslty through the RS232 port. No difference at all.

I have to admit that I have never guided trough USB but what should be better using USB ?

From my point of view ? Nothing.

Just to shot a few commands through a cable in order to get the mount moving faster or slower ?

By the way I use also the parallel port to control the shutter of my DSLR at the same time as I am guiding. No collisions at all. As Shoestring says it is a Pass through adapter and you just have to take care to use for other controlling software the free pins of the parallel port.

If you have a parlallel port use it and spare the USB port for other things.

Just my 2 cents

[74tuc]

Yes I agree with the last post - no difference between USB (usb to parallel) control and parallel port control which also allows DSLR shutter control.

The pins on the HEQ5's RJ12 connector indicate that it is ST4 compatible which means that it needs 4 sepatate signals (Dec-up/Dec-dn and Ra-up/Ra-dn) to autoguide with. This implies that it is a parallel connection so you may autoguide using the parallel port (via a protective relay box by Shoestring or home made etc). The USB interface (Shoestring's) is a USB to Parallel converter that installs as a "human Interface Device". One may also use a USB to Parallel interface - NOT the Dick Smith's variety. The commonly available "USB to Parallel converters" ($ 39)are DO NOT provide a parallel port (IEEE 1284 standard) but a PRINTER port only which is not what you want here. For a laptop the only one that that I know that is fully IEEE 1284 compliant is the "QUATECH SPP-100" pcmcia card:
http://www.quatech.com/catalog/parallel_pcmcia.php
These cards are somewhat expensive but they definitely work unlike other cheaper versions that somewhat work!!

Jerry.

[g__day (Matthew)]

Wrong!

The parallel port starts up in an undefined state in windows, the USB starts up in a power down state and is kept that way by the shoestring product.

So start a scope with parallel port attacher guider and things may go astray as I found. You can get by by creating a text file with a binary editor and writing binary null (00) to it then binary copying (copy /b ) this file as a start up service under windows to the LPT1 port

create a file called null.txt and a null.bat file with the follwoing DOS command in it, then add it as a scheduled task under Control Panel

copy /b c:\null.txt LPT1

The printer port remembers the last data written to it and keeps re-broadcasting, so writing binary zero fixes the issue - but what a hassle!

So I'd recommend the parallel port - and think this warning should be on the parallel port version!

[glasseyes (John)]

Thank you all for your valuable input.
I will try the serial option using the RS-232 com port of the PC into the RJ-11 SynScan handset and if that is not successful I will look at buying one of the Shoestring adapters. I think that I am leaning toward the USB option to keep things standard (less leads and adapters to worry about if everything uses USB).
Cheers all

[74tuc]

Re:
The parallel port starts up in an undefined state in windows, the USB starts up in a power down state and is kept that way by the shoestring product.

Whew!! Is that all thats wrong ?

But surely the cure is worse than the disease. I make the port connections after the guiding program initialises the port.

Jerry.

[g__day (Matthew)]

I leave my connections permanently wired between the mount and the observatory PC. So from mount and power on the mount will be getting slew commands from the parallel port if its not been last written by nulls - yucky.


glasseyes

If you're going to wire the serial port to the autoguider rather than the hand controller (and I do both for different purposes), use RJ12 wiring and - be very sure to use electro couplers with the right resistors / diodes wired the right way to prevent damage! This is what the shoestring products does (probably using 2-3 resistors, a capacitor and maybe an inductor in the right place). Alternatively you can try a design using two diodes http://www.bbastrodesigns.com/autoguide.html

You can find wiring diagrams on the net, it isn't as simple as RS232 pin 3 goes to pin in 1 of the autoguide port, the volatge and ampage and impedance have to be altered from the serial out to the autoguider in!

[glasseyes (John)]

Thanks for your input guys. I reckon I am convinced now. I can see why most people have gone for the Shoestring USB option.
1. The optocouplers protect the mount electronics against user/cable error.
2. Standardisation of cables (USB cables for nearly everything).
3. Provides for a future connection of a USB remote extender hub using a single CAT5 cable between the scope (out in the cold) and the PC (inside where it's warm). These will work up to 140 metres!
4. My next laptop probably won't have a parallel or serial port on it.

If I mount the Shoestring USB interface near the mount, all that I will need is one RJ-12 cable from the mount autoguider port to the interface box.
Serial ports, parallel ports, who needs 'em, USB - way to go !!

[ballaratdragons (Ken)]

I doubt if it makes any difference, but my shoestring interface is on my control desk, and I run a cable out to the mount.

At least I can see that the interface is sending signals. It has an LED that flashes when it sends pulses to the mount.