Introduction

System design requirements are continually changing as systems become increasingly complex. In conventional systems where sensors and actuators are connected directly to a microcontroller (MCU), the number of pins available on the MCU limits system expansion. As a result, extra costs can be incurred if another MCU is required or if the hardware has to be redesigned to accommodate a higher pin count MCU. An alternative approach is to move to a distributed bus architecture. This option allows one master MCU to interconnect to many remote sensors and actuators.

The DSI communication bus is simple yet robust. Signals are superimposed onto the power line and, as communication between the master and slave nodes is bi-directional, the DSI makes efficient use of bus bandwidth. Also, to ensure message integrity, each message contains a 4-bit Cyclic Redundancy Check (CRC).

Slave nodes can be attached to the bus in daisy chain or parallel connections. Each slave device on a bus has a unique address. The daisy chain connection allows the central module to establish the node addresses at power-up. The parallel configuration can be used for devices that have pre-programmed or fixed addresses. It is possible to have a combination of the two on one bus with the maximum number of nodes on a DSI bus being 16 (1 master and 15 slaves).