Knowledge Base

SX10507: Connecting to your controller

The board can connect to your controller in one of two ways: Via the 2 pin TTL Xwire connector or via an RS485 adaptor, if your controller does not have an RS485 Xwire interface. You have to decide which interface you are using, select it via a jumper and then connect to the corresponding external terminals.

Xwire is our proprietary serial peripheral bus. It consists of the Xwire electrical interface and the Xwire data protocol that is used to convey data across the interface and wiring. The 2 pin TTL Xwire electrical interface is good for a few feet and up to 10 boards. The final choice of interface is dependent on the distance and the electrical environment (ie: the amount of electrical noise).

RS485 is an industry standard electrical interface suitable for direct wire connection between devices located up to hundreds of feet apart. RS485 will allow up to 32 boards to be connected. The programming is exactly the same but you will be able to go further for the cost of an extra RS485/Xwire converter on the controller. The RS485 interface is a lot more forgiving in terms of noise and is better protected against electrical transients and ground loop problems.

Selecting the Xwire or RS485 interface

A 3-pin jumper on the board is labelled ‘RS485 X‘. Inserting a jumper in the two pins labelled RS485 will activate the RS485 interface. Inserting a jumper in the two pins labelled X will activate the Xwire electrical interface.

Connecting to the Xwire interface

Two connectors on one long side of the board are labelled X1 and X2. These are the TTL Xwire electrical connections. The two connectors are wired in parallel on the board to facilitate daisy chaining, and are completely interchangeable. The left-hand pin of each connector is ground (0V). If you are wiring to other boards with X1/X2 connectors, simply wire like pins together. If wiring to MMi202 or SL100, see the Xwire connection instructions in their documentation. See also wiring in the Xwire documentation.

Connecting to the RS485 interface

The 3-pin screw terminal block is for RS485 connection. The A and B terminals should go to A and B on all other devices on the RS485 system.

The G terminals on all boards in a system should all be connected together. For best results, especially over long distances and/or where the devices each end are powered off different power supplies, use shielded pair cable, and use the shield for the G connection.

Just next to the terminals (to the left above) is a jumper marked “Term”. Installing a jumper in that position provides an RS485 line termination resistor. At the 38400 baud used by Xwire termination is not very critical. One termination resistor in a complete system is generally adequate.