HMILink: a zero-code programming system for embedded screen-type HMI

With the development of IoT(Internet of Things) technology, the number of IoT applications which involve embedded screen-type HMI is increasing rapidly. The development of embedded HMI programming needs to go through the procedure of UI programming, embedded programming, back-end programming, etc. Because of the long development chain and the high requirements for developers, embedded HMI programming has not only the weakness of high expenditure and long development period, but also the pain point of long iteration and difficulty in later upgrading. This paper designs and implements an embedded HMI zero code system, including screen driver module, screen event processing module, format conversion module and MQTT link module on the embedded side; micro-service router module, various microservices, format conversion module and MQTT link module on the background server side. This system achieves the goal of zero code on embedded end by the means of using screen drive module to migrate the embedded HMI FSM to background server; screen event processing module to realize the display of HMI data controls. The micro-service router transmits the HMI events to each microservice through the micro-service router module, which uses 1-to-1 mapping mode between events and microservices, and the mapping relationship is stored in the relational database. To discriminate different HMI terminals, K/V database is used to store business process number and business intermediate data, which are differentiated through different tags. Experiment results are consistent with system design, The HMI interaction average delay time is 3ms after passing through the screen event module and screen drive module, which is at the same level as traditional embedded HMI applications; by passing the zero code middleware, the embedded end code is reduced to zero, the back-end code is increased by about 10%, and the overall development time is reduced by 30%. The practice of intelligent manufacturing digital factory indicates that zero code is realized at the embedded HMI end, the back-end code is only increased by 10%, and the overall development cycle is shortened by 30%; The practice of smart home shows that zero code is realized at the embedded HMI end, the back-end code is only increased by 5%, and the overall development cycle is shortened by 20%.