WiFi Modbus Gateway for Danfoss EKC 202C
Budget: $250 – $750 USD
Project Overview
This project aims to develop a small WiFi gateway that connects to a Danfoss EKC 202C refrigeration
controller via Modbus RTU (RS-485) and provides a local web interface. The system should allow
monitoring of key controller values and limited control via a browser. The first version is a local-only
solution without cloud connectivity, but the architecture must allow future expansion to cloud services.
Hardware Assumptions
• ESP32 or similar WiFi-enabled microcontroller
• RS485 interface module for Modbus RTU communication
• Connection to Danfoss EKC 202C controller (via Modbus adapter)
Setup Flow
• On first boot the device starts its own WiFi Access Point
• User connects via smartphone or laptop
• User opens configuration page at 192.168.4.1
• User enters WiFi SSID, WiFi password, and device name
• Device connects to the local network and becomes reachable via hostname (example:
http://coolroom1.local)
Core Features
1. Live Data Monitoring
• Current air temperature
• Temperature setpoint
• Fan status
• Cooling / compressor / solenoid status
• Defrost status
• Alarm status
• Last successful update timestamp
2. Temperature Logging
Temperature values should be logged every 60 seconds and stored locally for 24 hours. This results in
approximately 1440 data points per day. The web interface should display a 24-hour temperature chart.
3. Setpoint Modification
• Display current setpoint
• Allow user to enter a new setpoint
• Send new value to controller via Modbus
• Read back value to confirm successful change
4. Web Interface
• Temperature display
• Status icons for fan, cooling, alarm
• 24-hour temperature chart
• Parameter view
• Setpoint modification form
• Responsive layout for smartphones, tablets, and desktop browsers
Important Technical Requirements
• Separate Modbus communication layer
• Internal API for system data (example: /api/status, /api/temperature)
• Modular architecture separating Modbus, storage, web server and UI
Not Included in Version
• Cloud connectivity
• Remote internet access
• Multi-device dashboard
• User accounts
• OTA firmware updates
Deliverables
• Working firmware
• Source code
• Wiring diagram
• Setup instructions
• Documentation of Modbus register mapping used
Expected Timeline
Estimated development time: 1–2 weeks.
Future Expansion
The architecture should allow future cloud integration where the gateway can send data to a remote server
(e.g., MQTT or HTTPS API) for remote monitoring and multi-device dashboards
This project aims to develop a small WiFi gateway that connects to a Danfoss EKC 202C refrigeration
controller via Modbus RTU (RS-485) and provides a local web interface. The system should allow
monitoring of key controller values and limited control via a browser. The first version is a local-only
solution without cloud connectivity, but the architecture must allow future expansion to cloud services.
Hardware Assumptions
• ESP32 or similar WiFi-enabled microcontroller
• RS485 interface module for Modbus RTU communication
• Connection to Danfoss EKC 202C controller (via Modbus adapter)
Setup Flow
• On first boot the device starts its own WiFi Access Point
• User connects via smartphone or laptop
• User opens configuration page at 192.168.4.1
• User enters WiFi SSID, WiFi password, and device name
• Device connects to the local network and becomes reachable via hostname (example:
http://coolroom1.local)
Core Features
1. Live Data Monitoring
• Current air temperature
• Temperature setpoint
• Fan status
• Cooling / compressor / solenoid status
• Defrost status
• Alarm status
• Last successful update timestamp
2. Temperature Logging
Temperature values should be logged every 60 seconds and stored locally for 24 hours. This results in
approximately 1440 data points per day. The web interface should display a 24-hour temperature chart.
3. Setpoint Modification
• Display current setpoint
• Allow user to enter a new setpoint
• Send new value to controller via Modbus
• Read back value to confirm successful change
4. Web Interface
• Temperature display
• Status icons for fan, cooling, alarm
• 24-hour temperature chart
• Parameter view
• Setpoint modification form
• Responsive layout for smartphones, tablets, and desktop browsers
Important Technical Requirements
• Separate Modbus communication layer
• Internal API for system data (example: /api/status, /api/temperature)
• Modular architecture separating Modbus, storage, web server and UI
Not Included in Version
• Cloud connectivity
• Remote internet access
• Multi-device dashboard
• User accounts
• OTA firmware updates
Deliverables
• Working firmware
• Source code
• Wiring diagram
• Setup instructions
• Documentation of Modbus register mapping used
Expected Timeline
Estimated development time: 1–2 weeks.
Future Expansion
The architecture should allow future cloud integration where the gateway can send data to a remote server
(e.g., MQTT or HTTPS API) for remote monitoring and multi-device dashboards