Pinouts for rs232 cable

[greywolf]

Hello all,

          I have just been looking on ebay and found some cables to control my telescope that have a serial plug one end and what looks like a db4 phone plug the other.

They are cheap enough to buy but all take a while to ship. However I have both ends and a heap of cable here at home if I can find the pinouts to make one myself.

I have a Celestron Nexstar 130 and a laptop with a serial port running Stellarium. If anyone has made one I would love a link to the pinouts, that way I could make a control cable of a decent length and not have to wait for shipping.

Any suggestions would be greatly appreciated.

Cheers

[gkec]

http://www.nexstarsi.../RS232Cable.htm

Note that this plugs into the hand controller, not the mount which uses TTL level signals not RS232 signals.

[greywolf]

http://www.nexstarsi.../RS232Cable.htm

Note that this plugs into the hand controller, not the mount which uses TTL level signals not RS232 signals.

Thank you for that, you mean the plug on the bottom of the keypad, didnt even notice it had one till your post.  So what is the advantage/disadvantage to connecting there and via the spare plug near the power plug on the base. Does one offer an more functionality?

Thanks again.

[gkec]

Thank you for that, you mean the plug on the bottom of the keypad, didnt even notice it had one till your post.  So what is the advantage/disadvantage to connecting there and via the spare plug near the power plug on the base. Does one offer an more functionality?

Thanks again.

The one on the bottom of the handset connects to the computer in the handset and is rs232.  This allows you to talk to the handset computer and tell it to go to a RA/DEC position things like that.  This is used by many of the mount control packages available.

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

The mount as mentioned uses TTL level serial and it is almost certainly a "lower level" protocol that allows the handset to move the RA and DEC motors. I don't know if this protocol is documented anywhere.

As it uses TTL you would have to get a USB to TTL cable which is different to the RS232 more usually found.  If you connect TTL to RS232 it will probably be damaged as the RS232 voltages are a lot higher (typically +-12Volts v 5Volts )