CANopen / SAE J1939 / SSI
Control Area Network (CAN) bus, is a high-integrity serial bus system originally created as an automotive vehicle bus, which later came to be used as one of the fieldbuses for industrial automation. CANopen® is a CAN-based communication system. It comprises higher-layer protocols and profile specifications and provides a physical and data link layer for serial communication with speeds up to 1 Mbps. CANopen® and DeviceNet™ are higher level protocols standardized on top of CAN bus to allow interoperability with devices on the same industrial network. CANopen® supports 127 nodes on the network while DeviceNet™ supports 64 nodes on the same network.
EPC CANopen® encoders use communication profile CiA 301 and device profile CiA 406 V3.2 class C2.
SAE J1939, a set of standards defined by the Society of Automotive Engineers (SAE), is primarily used for communication and diagnostics in heavy-duty vehicles like trucks, buses, and construction equipment, as well as other commercial vehicles.
J1939 defines how Electronic Control Units (ECUs) transmit data over the Controller Area Network (CAN) bus protocol, enabling communication and diagnostics between vehicle components.
It creates a universal shared “language” for devices to interact, allowing heavy-duty vehicles to be fitted with devices from different manufacturers without worrying about incompatibility.
Synchronous Serial Interface, or SSI, is a commonly used point-to-point serial communications protocol. It is widely used in industrial applications due to its simplicity and proven history. SSI is the most straight-forward communication protocol that EPC offers for its absolute encoders. SSI is a master/slave technology; the controller serves as the master device and the encoder acts as the slave device. The master controls the speed of data transfer based on clock frequency; each clock pulse from the master prompts a response of 1 bit of information from the slave device until the entire packet has been received. The graphic below illustrates the master/slave relationship:
