Operators of construction equipment, agricultural machinery, mining vehicles, and other mobile machines need a reliable way to interact with the machine.
Two common operator interfaces are:
An HMI can display machine data, alarms, operating modes, and diagnostic information, while a CAN keypad provides physical buttons for fast and direct operation.
So which interface should an OEM choose?
The answer depends on the machine, the operating environment, and the type of functions the operator needs to control. In many applications, the best solution is not HMI or CAN keypad, but a combination of both.
An HMI (Human-Machine Interface) is a display that allows the operator to monitor and interact with the machine.
A mobile machinery HMI may display:
Engine information
Hydraulic pressure
Fuel level
Machine speed
Operating modes
Sensor values
Warning messages
Fault codes
Maintenance information
Depending on the HMI, operators may interact through a touchscreen, physical keys, rotary controls, or a combination of these methods.
A typical architecture is:
Sensors / ECU
↓
Mobile Controller
↓
CAN
↓
HMI Display
↓
Operator
The HMI is particularly useful when a machine needs to present a large amount of information through a single interface.
A CAN keypad is a physical button panel that communicates with the controller through CAN Bus.
Instead of wiring every switch individually to controller inputs, the keypad can send button status and commands over CAN.
English
Operator
↓
CAN Keypad
↓
CAN Bus
↓
Mobile Controller
↓
Machine Function
Buttons can be assigned to functions such as:
Work lights
Hydraulic attachments
Fan control
Auxiliary functions
Operating modes
Machine settings
Function enable/disable
LED indicators can also provide visual feedback about the status of a function.
The main difference is the type of interaction they provide.
| Feature | HMI Display | CAN Keypad |
|---|---|---|
| Information display | Excellent | Limited |
| Physical buttons | Depends on model | Yes |
| Fault diagnostics | Excellent | Limited |
| Parameter settings | Excellent | Limited |
| Frequent machine commands | Suitable | Excellent |
| Visual machine data | Excellent | Limited |
| Menu navigation | Yes | Usually limited |
| Direct tactile feedback | Depends on interface | Excellent |
| Customizable interface | High | Function-dependent |
An HMI is primarily suited to information, visualization, settings, and diagnostics.
A CAN keypad is particularly suited to direct and frequently used machine commands.
An HMI is useful when the operator needs to see and manage a significant amount of machine information.
The HMI can combine multiple operating parameters on one screen.
For example:
ENGINE SPEED 1850 rpm
HYD. PRESSURE 210 bar
COOLANT TEMP. 82 °C
FUEL LEVEL 68%
Instead of installing separate gauges and indicators, this information can be integrated into the HMI.
When the controller detects a fault, the HMI can provide detailed information.
For example:
HYDRAULIC SYSTEM FAULT
Boom Valve Output
Open Circuit
Check wiring and connector.
This provides considerably more information than a single warning lamp.
HMIs are also suitable for settings such as:
Speed limits
Hydraulic parameters
Operator preferences
Attachment selection
Maintenance intervals
A menu-based interface makes it possible to manage many parameters without adding more physical switches.
A CAN keypad is useful for functions that operators need to activate quickly and repeatedly.
For example, an operator may frequently control:
Work lights
Auxiliary hydraulics
Attachments
Fans
Machine modes
With dedicated physical buttons, the operator does not need to navigate through several HMI menus to find a function.
This can be particularly useful when the operator is wearing gloves or needs to operate the machine while concentrating on the work area.
A physical button can provide a simple interaction:
Press Button
↓
CAN Message
↓
Controller
↓
Work Light ON
The button LED can then indicate that the function is active.
One important consideration is how frequently a function is used.
Imagine an operator needs to switch an auxiliary hydraulic function on and off many times during a working shift.
If the function requires:
HMI Home
↓
Hydraulic Menu
↓
Attachment Menu
↓
Enable
the interaction may become unnecessarily complicated.
A dedicated keypad button can provide faster access.
By contrast, a function such as changing a maintenance interval or reviewing a fault history may only be used occasionally. These functions are much better suited to an HMI menu.
A practical rule is:
Frequent command → physical control
Detailed information or configuration → HMI
In many mobile machines, the most effective solution is to use both interfaces.
For example:
Operator
↙ ↘
CAN Keypad HMI
↘ ↙
CAN Network
↓
Mobile Controller
↓
Machine Functions
The CAN keypad handles frequent commands, while the HMI provides detailed information and configuration.
The operator can quickly control:
Work lights
Hydraulic functions
Attachments
Fan functions
Common operating modes
The operator can view or configure:
Engine data
Hydraulic pressure
Sensor information
Fault diagnostics
Machine settings
Maintenance information
The controller receives commands from both interfaces and executes the machine control logic.
This separates frequent operation from information and configuration.
Consider an excavator equipped with a mobile controller, HMI, and CAN keypad.
The keypad might provide dedicated controls for:
[LIGHTS] [AUX 1] [AUX 2]
[FAN] [MODE] [ENABLE]
Meanwhile, the HMI could display:
Engine Speed
Hydraulic Pressure
Coolant Temperature
Fuel Level
Operating Mode
Active Faults
If the controller detects a hydraulic sensor fault, the HMI can display detailed diagnostic information.
The keypad does not need to reproduce this information. Its purpose is to provide quick access to commonly used functions.
Each interface therefore performs the task for which it is better suited.
Traditional physical switches may require individual wiring back to controller inputs.
For example:
Switch 1 ─────────→ Digital Input 1
Switch 2 ─────────→ Digital Input 2
Switch 3 ─────────→ Digital Input 3
Switch 4 ─────────→ Digital Input 4
A CAN keypad can consolidate multiple commands through a CAN connection:
┌─────────────────┐
│ CAN Keypad │
│ 1 2 3 4 5 │
└────────┬────────┘
│
CAN Bus
│
↓
Mobile Controller
This can reduce the number of individual signal wires required between the operator panel and controller.
The exact wiring benefits depend on the overall machine architecture and keypad design.
The choice should be based on the actual operator workflow rather than simply selecting the interface with the most features.
OEM engineers should consider:
How many functions need operator control?
Which functions are used frequently?
How much machine information must be displayed?
Are detailed diagnostics required?
Does the operator need parameter configuration?
Will operators frequently wear gloves?
How quickly must important functions be accessed?
What CAN architecture is already used in the machine?
Is a combined HMI and keypad interface more practical?
The physical installation environment should also be considered, including vibration, dust, moisture, temperature, visibility, and available panel space.
Rather than treating the HMI and CAN keypad as isolated components, they can be designed as part of the complete machine control architecture.
For example:
Engine ECU ────────┐
Sensors ───────────┤
Remote I/O ────────┤
↓
Mobile Controller
↙ ↘
CAN Keypad HMI
↓ ↓
Quick Commands Monitoring
Diagnostics
Configuration
The controller remains responsible for the machine logic, while the HMI and keypad provide different forms of operator interaction.
This allows OEMs to create an interface that is both informative and practical to operate.
HMI displays and CAN keypads serve different purposes in mobile machinery.
An HMI is better suited to:
Machine visualization
Sensor data
Parameter settings
Fault diagnostics
Complex information
A CAN keypad is better suited to:
Frequently used commands
Direct physical operation
Dedicated machine functions
Fast access without menu navigation
For many mobile machines, the best solution is therefore not HMI vs CAN keypad, but:
HMI + CAN Keypad + Mobile Controller
By assigning each interface to the functions it handles best, OEMs can create a control system that provides both detailed machine information and efficient operator interaction.
