RS-485 Communications in Benchmark Games

Benchmark's R&D department is constantly developing new concepts for our industry, always looking for ways to incorporate new technologies so that our games will contain a high level of features without a dramatic increase in cost. In other words, trying to give more "Bang for the Buck."

For this reason, we have implemented the use of RS-485 serial communications in all of our games. This allows for more versatility as well as smaller and less complicated harnessing.

RS-485 serial communications is a technology that has been used in industrial environments for many years. It has proven to be immune to the electrical noise and interference that is so common in arcades and FEC's.

In each of our games, all of the Printed circuit boards (PCB's) communicate with each other using RS-485, which requires only two wires. The Main Controller acts as the "Master," and all of the other PCB's are "Slaves." The Main Controller sends commands to the different boards, and receives data in return or simply an answer indicating that the board received the command. Each Slave has a unique address that is set by the dip switches on the board. The simple two wire connection is "daisy chained" from one board to the next.

The main controller is constantly communicating with the different boards to ensure that they are online and operational. This allows for better diagnostics of the entire game.

If there is a problem with the communications, such as a board not responding, it is usually one of two things:

1. The RS-485 two-wire bus is broken or disconnected. Since it is daisy-chained, this is usually easy to track down because all of the boards that are "upstream" of the break will continue to operate, while all of the ones downstream will not respond.

2. The dip switches are not set correctly. Since each board has a unique address that is called by the Main Controller, if the dip switches are not set correctly the board will not respond to the command.

In many cases Benchmark Games’ in-house design team uses a different philosophy than others in the industry in order to deliver higher performance and reliability. As in the case of the RS-485 serial communications, a basic understanding can help you with your operation.