When you are working on the human-machine interface of a device, you are likely to encounter these situations: the microcontroller cannot display a good-looking interface, the host computer touch screen is too expensive, or the built-in HMI of the PLC is not flexible enough. The serial port screen is born for such scenarios - a module with an MCU and a screen, where you just need to bind the variable address to the control, and the screen handles the display and touch by itself, while the underlying communication is handled by the screen firmware.
VisualHMI is a configurable serial port screen development platform launched by Guangzhou Dacai Technology. It is different from the "drag a few buttons and done" screens on the market. The core selling point isvariable drive + complete separation of UI and control logic: you draw the interface and bind variables on the PC software, while the screen firmware is responsible for parsing messages and refreshing controls. You only need to touch the variable address when writing business logic, without worrying about how the screen describes points.
First, what practical problems does it solve?
To put it simply: originally, you had to use an MCU to directly drive the LCD, and just a curve graph and a Chinese input method could take half a month. With VisualHMI, these become drag-and-drop controls + a few lines of LUA. For projects with tight deadlines, this is a qualitative difference.
| Pain points | How does VisualHMI solve the problem of |
|---|---|
| MCU driving the screen, with a large amount of development work? | There are 30+ types of configurable controls, which can be dragged and used, with 100% preview and restoration. |
| Switching between multiple languages is troublesome. | One-click switching, up to 30 languages |
| To communicate with Modbus/PLC | Native integration of Modbus master/slave, FX2N, Delta, Xinye, Siemens PPI, etc. |
| To perform data recording/curve plotting | Built-in historical curve, data recording, alarm recording, operation recording |
| Complex logic is not supported | LUA scripting, register operations/timers/custom protocols can be written |
II. List of supported communication protocols
VisualHMI firmware runs directly on M-series hardware, with the protocol stack built-in. You just need to check in the project:
- DCBUS: Dacai's own configuration protocol, with a default frame header of 0xAA55, suitable for interfacing with proprietary motherboards
- XGUS: Another configuration protocol, with a default frame header of 0x5AA5
- Modbus RTU: Standard protocol, configurable as Master or Slave - this is the most relevant part for readers of modbus.cn
- FX2N / FX3U: Mitsubishi PLC protocol
- DELTA DVP: Delta PLC
- XINJE XC / XD: XINJE PLC
- FATEK FB: FATEK PLC
III. What Does the Development Process Look Like?
A Typical Development Path is as Follows:
- Install VisualHMI configuration software on a PC, create a new project, select a screen model
- Draw a screen, drag controls, and bind the controls to variable addresses (LW user area / system area)
- Configure communication protocols in the project properties (such as Modbus Master, set baud rate, slave number)
- Write LUA to handle complex logic (reading from the slave, calculating total electricity, alarm judgment, etc.)
- Download to the screen via SD card or serial port
- Debug the virtual screen online, using Modbus Slave software to simulate the slave for verification
The following column will break down each section in the order of "Quick Start → Resources → Configuration Controls → Data Recording → LUA → Other → FAQ", focusing on practical examples and avoiding unnecessary details. The next article will delve into protocol details, especially how to configure Modbus master and slave and how to assemble frames.
This article is compiled from the VisualHMI development documentation of Guangzhou Dacai Technology (hmi-doc.gz-dc.com), copyright reserved by Dacai Technology. It is rearranged from an engineer's perspective for technical learning and reference purposes only.
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