BS2 serin and serout communication through RS-485 cable

lindseydallas

Hello,

Is it possible to have communication through an RS-485 cable using the Serin and Serout commands on the BS2? My program works using a USB cable and USB2Ser board, but I need to convert it to RS-485 to allow the connection to go longer distances and possibly in the future be a multi-drop network. The Serin and Serout commands each have a transmit and receive pin, but from what I understand of RS-485, being a "balanced" signal, it actually uses both wires at the same time.

Any insight would be appreciated!

Phil Pilgrim (PhiPi)

For RS485, you will need an additional transceiver chip to provide the balanced signalling. One example is this one:

http://www.digikey.com/product-detail/en/SP485ECP-L/1016-1170-5-ND/2411102

You can connect RI and DO together to one BS2 pin (used for both SERIN and SEROUT), and /RE and DE together to another BS2 pin to control the direction.

-Phil

Publison

There is a good column in Nuts and Volt on RS-485 with the BS-2:

http://www.parallax.com/downloads/nuts-and-volts-basic-stamps-volume-1

Column #28

Genetix

Just remember that the BS2 doesn't have a buffer and it can only do 1 thing at a time.

Publison

Genetix wrote: »

Just remember that the BS2 doesn't have a buffer and it can only do 1 thing at a time.

I see to remember the BS2 can only do Half Duplex on RS-485?

Phil Pilgrim (PhiPi)

Publison wrote:

I see to remember the BS2 can only do Half Duplex on RS-485?

RS-485 is a half-duplex mode for any micro. And, yes, the BS2 can only do half-duplex anyway, since it's single-tasking; so there's nothing to be gained from going to RS-422, which is full-duplex.

-Phil