# Heltec HRI-4853

> ESP32-based RS-485 to Ethernet/LTE converter (DTU) with built-in web configuration, Modbus support, DIN-rail mounting, and ESPHome compatibility for industrial IoT and Home Assistant integration.

## Quick Facts

- **Brand:** Heltec Automation
- **Board Type:** DTU
- **Price:** ~$22.9
- **CPU:** Xtensa LX6 dual-core @ 240MHz, FPU, hardware crypto (AES/SHA)
- **CPU Architecture:** Xtensa LX6
- **CPU Cores:** 2
- **RAM:** 520KB SRAM
- **Flash:** 4MB (QSPI)
- **USB:** None (UART-based programming)
- **Power:** 4.5-28V DC wide input
- **Operating Voltage:** 3.3V
- **Operating Temp:** -40°C to +85°C
- **Dimensions:** 120 × 70 × 32mm
- **Weight:** 90g
- **Antenna:** SMA (glue rod antenna included)
- **SD Card:** No

## Connectivity

- **Wifi:** 802.11 b/g/n
- **Bluetooth:** Bluetooth 4.2, BLE
- **Ethernet:** 10/100 Mbps (RTL8201 PHY)

## Use Cases

- modbus-gateway
- rs485-to-ethernet
- industrial-controller
- building-automation
- energy-monitoring
- smart-home

## Components

- **ESP32-D0WDQ6** (mcu): Espressif ESP32-D0WDQ6 dual-core Xtensa LX6 @ 240MHz with 520KB SRAM, WiFi 802.11 b/g/n, Bluetooth 4.2, and hardware AES/SHA crypto acceleration. — [Datasheet](https://openhardware.directory/r?to=https%3A%2F%2Fwww.espressif.com%2Fsites%2Fdefault%2Ffiles%2Fdocumentation%2Fesp32_datasheet_en.pdf&ref=openhardware.directory&product=heltec-hri-4853&source=md-export)
- **RTL8201** (ethernet-phy): Realtek RTL8201 single-chip 10/100 Mbps Ethernet PHY transceiver with RMII interface for wired network connectivity. — [Datasheet](https://openhardware.directory/r?to=http%3A%2F%2Frealtek.info%2Fpdf%2Frtl8201.pdf&ref=openhardware.directory&product=heltec-hri-4853&source=md-export)
- **MAX3485** (rs-485-transceiver): Maxim MAX3485 3.3V low-power half-duplex RS-485/RS-422 transceiver with 10 Mbps data rate, fail-safe receiver, and thermal shutdown protection. — [Datasheet](https://openhardware.directory/r?to=https%3A%2F%2Fwww.analog.com%2Fen%2Fproducts%2Fmax3485.html&ref=openhardware.directory&product=heltec-hri-4853&source=md-export)

## Protocols

- **Ethernet RMII**: MDC: GPIO23, MDIO: GPIO18, CLK: GPIO17
- **UART (Modbus RS-485)**: TX: GPIO33, RX: GPIO37
- **RS-485**: Power Control: GPIO16

## GPIO Map

| Pin | Name | Type | Functions |
|-----|------|------|-----------|
| GPIO2 | HA Online LED | LED | digital-input, digital-output, pwm, adc, touch |
| GPIO3 | Status LED | LED | digital-input, digital-output, pwm |
| GPIO16 | MAX3485 Power Control | GPIO | digital-input, digital-output, pwm |
| GPIO17 | Ethernet RMII CLK | Ethernet | digital-input, digital-output, pwm |
| GPIO18 | Ethernet MDIO | Ethernet | digital-input, digital-output, pwm |
| GPIO23 | Ethernet MDC | Ethernet | digital-input, digital-output, pwm |
| GPIO33 | Modbus UART TX | UART | digital-input, digital-output, pwm, adc |
| GPIO37 | Modbus UART RX | UART | input-only |

## Description

## Overview

The Heltec HRI-4853 is an industrial-grade Data Transfer Unit (DTU) that bridges RS-485 serial devices to IP networks via Ethernet or LTE. Built around the ESP32-D0WDQ6 dual-core MCU, it converts Modbus RTU data from RS-485 sensors and actuators into TCP, UDP, or MQTT packets, enabling remote monitoring and control of industrial equipment over standard network infrastructure.

The device features a wide 4.5-28V DC power input, an industrial operating temperature range of -40 to +85 degrees Celsius, and a DIN-rail compatible enclosure rated IP65. Configuration is handled through a built-in web interface accessible over WiFi at 192.168.4.1 — no external software is required. The RS-485 interface supports baud rates from 1200 to 115200 bps with a 1024-byte buffer and up to 240-byte single packets.

Thanks to its ESP32 foundation and the MAX3485 RS-485 transceiver, the HRI-4853 can be flashed with ESPHome firmware for deep integration with Home Assistant. The ESPHome configuration exposes Modbus sensor readings directly as Home Assistant entities, making it an excellent bridge between legacy industrial sensors (temperature, humidity, energy meters) and modern smart home or building automation systems. An RTL8201 Ethernet PHY provides reliable 10/100 Mbps wired connectivity for always-on deployments.

## Where to Buy

- [Heltec Official Store](https://openhardware.directory/r?to=https%3A%2F%2Fheltec.org%2Fproject%2Frs4853-tcp-udp-mqtt-converter%2F&ref=openhardware.directory&product=heltec-hri-4853&source=md-export) — 22.90

## Resources

- [product](https://openhardware.directory/r?to=https%3A%2F%2Fheltec.org%2Fproject%2Frs4853-tcp-udp-mqtt-converter%2F&ref=openhardware.directory&product=heltec-hri-4853&source=md-export)
- [wiki](https://openhardware.directory/r?to=https%3A%2F%2Fdocs.heltec.org%2Fen%2Fready_to_use%2Fhri-485x%2Findex.html&ref=openhardware.directory&product=heltec-hri-4853&source=md-export)
- [datasheet](https://openhardware.directory/r?to=https%3A%2F%2Fresource.heltec.cn%2Fdownload%2FHRI-485X%2FHRI-485x.pdf&ref=openhardware.directory&product=heltec-hri-4853&source=md-export)
- [github](https://openhardware.directory/r?to=https%3A%2F%2Fgithub.com%2FHelTecAutomation&ref=openhardware.directory&product=heltec-hri-4853&source=md-export)

## Tags

`rs485`, `modbus`, `ethernet`, `dtu`, `industrial`, `esp32`, `esphome`, `home-assistant`, `din-rail`, `mqtt`

## Images

![Heltec HRI-4853](https://nbg1.your-objectstorage.com/openhardware-directory/entities/heltec-hri-4853/39d68fc5e506.png)
![Heltec HRI-4853](https://nbg1.your-objectstorage.com/openhardware-directory/entities/heltec-hri-4853/429044ba3e36.png)
![Heltec HRI-4853](https://nbg1.your-objectstorage.com/openhardware-directory/entities/heltec-hri-4853/36b94b0dfc18.png)
![Heltec HRI-4853](https://nbg1.your-objectstorage.com/openhardware-directory/entities/heltec-hri-4853/122dfc8b1e4d.png)
![Heltec HRI-4853](https://nbg1.your-objectstorage.com/openhardware-directory/entities/heltec-hri-4853/0c30f5514bbc.png)

---
[View full device page](https://openhardware.directory/devices/heltec-hri-4853)