Dealing with 15 pin Rs485 motor

[Sonderval]

Hey folks,

Having some great fun trying to figure out a way to hook up a serial RS485 motor to a PC. The clincher is that the damm thing is a sub D-15 pin connection and it seems most of the pins are used. Since there is a total absence of serial 15 pin PCI cards out there, I am turning to more esoteric means of hooking this motor up via some DAQ card. Thing is, I am not too sure what type of setup this would entail (and I have my eye firmly on a low cost solution). Does anyone have any ideas on dealing with a DAQ driven soltuion?

Thanks!

[Dennis_Knutson]

If it's truly RS-485, the cheapest and simplest solution would be a custom cable that you make or buy and connect that between the motor and any RS-485 interface in the pc. Trying to re-create a serial communication protocol with a DAQ board would require a failrly expensive board with hardware timed digital I/O and some voltage shifting to convert the TTL signals to RS-485 levels, and quite a bit of programming.

[Brian_Beal]

I think there is something missing here.  The RS-485 standard has no standard pinouts, so you would have to make your own cable anyways.  You say most of the pins are used, but I don't understand how that would affect the 485 comms.  What motor is it?

[Sonderval]

Its a stepper motor - I've listed the pinouts that the manual alludes too (this is possibly the worse manual I have ever read - spelling mistakes, incorrect grammar and non-sensical statements. Makes a strong case for proper documentation!)

1 + AT         Vdc
2 GND         Gnd
3 OUT1       Drive OK
4 OUT2       Motor status
5 In1            Direction
6 In2            Set microstep
7 InEn         Enable
8 RX-          RS485-
9 + AT         Vdc
10 GND      Gnd
11 Common  I/O Common
12 In3         Clock
13 In4         Set microstep
14 In5         Set microstep
15 RX+       RS485+

I guess the real problem here is the fact that the market only has either 9 or 25 pin PCI cards available - I have not see a single 15 pin serial card out there. Hence the idea of using some sort of alternate setup.

Any thoughts?

[Brian_Beal]

Again, a 15 pin serial card would do you no good.  Most of the signals are related to the stepper motor, not the 485 comms.  Making your own cable is the best answer.  Take your 15 pins to a terminal strip or breakout box and go from there to connect the proper signals.

[Sonderval]

Ok, I see what your implying - so my custom cable gets broken down into its 15 constituent connections, leading into the BOB. Where I am falling down is with regards talking with this BOB - if the stepper motor is expecting serial coms on 15 pins, and my PC only has 9 pin serial connections, then even with the breakout box in-between, is there not an obvious disparity between the 15 pins on the motor and the 9 pins on the PC?

Or am I missing something painfully obvious?

Stepper Motor --- via DB15 RS485 serial -----> Breakout Box ----------> 9 Pin Rs485 PCI card

[Brian_Beal]

Only 2 (or possibly 3 if a common is used) pins are used for the 485 comms.  The rest of the connections have nothing to do with comms and should be connected elsewhere.

[Sonderval]

Well, where else should they be connected? 3 wires for the RS485 as you mentioned, that leaves 12 more connections to be made, with only 7 points left on the serial port PCI card. Are you suggesting having those 3 wires hooked to the PC and they having the remaining being hooked to some standard DAQ card?

[Dennis_Knutson]

You may or may not have to connect the other signals to anything. Without seeing the data sheet for the motor, I don't know. It's possible that the vendor just bundled all possible connections into a single connector. If you have the option to control the motor with RS-485 or with discrete signals, then pick the control method you prefer - either serial or a DAQ card. If the RS-485 interface does not provide full control or it turns out that a serial connection is too slow, then directly control/monitor the motor with the DAQ board. Presumably, you have the manual on it. What does it say? If you need help in understanding the manual, post it here or provide a link to it.

[Sonderval]

Here is the motor in question, and its relevant data sheets/manuals.

Thoughts?