Re: [CAD_CAM_EDM_DRO] RS-422 help please.

audiomaker2000 wrote:

> Thanks for looking....
>
> I have a machine that uses the RS-422 protocol.
>
> The pin-"in's" for the machine's connector (AMP style) are
>
> Pin 1/ Function: Receive / Direction: Input / Polarity: Positive
>
> Pin 2/ Function: Receive / Direction: Input / Polarity: Negative
>
> Pin 3/ Function: Transmit / Direction: Output / Polarity: Negative
>
> Pin 4/ Function: Transmit / Direction: Output / Polarity: Positive
>
> Pin 5/ Function: Shield / Polarity: Ground
>
> I'm familiar to some extent with RS-232, but I'm not sure where to
> get these values from the computer.

You can't. RS-232 is "single-ended", ie. there is one pin carrying
the information, and its voltage is compared to the signal ground pin.

RS-422 is differential, the information is carried on 2 pins, one going
positive and the other negative. The signal is derived by comparing
the two pins. If P is more positive than N, that is a one bit, if N is more
positive than P, that is a zero.

> I would really like to use the
> DB-9 connector if possible, but If I have to, I could use the DB-
> 25...except my program only allows for com1-com2 communication.

Either will work, but you need to get an RS-422 to RS-232 converter.
The outfits that sell networking gear (Data Comm Warehouse, Black
Box, etc.) have these available.

Jon