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Cascadas Protocol:

Firefox on Linux

MB-HMI uses the Cascadas Protocol to communicate between the web browser and the data server (e.g. MBLogic or HMIServer). Cascadas is an open protocol designed for HMI applications.

The Cascadas protocol is based on JSON (Javascript Object Notation). It has the following characteristics:

Tag based addressing

Tag based addressing allows the client (browser) to address data elements independently of the physical data table addresses.

Read and write data

Integer, floating point, and string data types are supported. The protocol representation avoids problems caused by native word size or byte ordering.

Events, Alarms, and Alarm History

Events, alarms, and alarm history is directly supported. The use of "zones" allows events and alarms to be filtered according to origin.

Error detection and reporting

Protocol or data errors are reported back to the client.

Multiple operations in a single transaction

Multiple read and write operations can take place in a single transaction. This minimises the number of messages required, reducing bandwidth requirements and processing overhead.

Flexible Protocol:

The Cascadas protocol is flexible and can be adapted for other applications in addition to HMIs. For example, the read and write capabilities are idea for enterprise data integration (e.g. ERP).

Most programming languages have JSON parsers, which makes implementing the Cascadas protocol on new platforms relatively simple. The tag based addressing hides the machine control details from the other systems, and also allows memory write protection to avoid unintentional over writing of machine control addresses.

Protocol Specification:

The current draft of the Cascadas protocol can be found here: Cascadas Protocol Document This is a draft version, and is subject to revision.