A public technical documentation edition covering module overview, chip solution, pin definitions, performance parameters, reference circuit, AT command configuration, PCB layout guidelines, module usage and application experiments with open-source driver and sample code.

Module Overview

The BLE Bluetooth module based on EBYTE E104-BT02 implements Bluetooth communication using the E104-BT02 serial-to-BLE module. The module is built on the Dialog DA14580 solution, operates in the 2.4GHz ISM band, and integrates the BLE protocol stack, advertising and connection management, transparent transmission and serial AT-command configuration. The module operating voltage is 2.5~3.6V (3.3V recommended); the carrier board in this project accepts +5V input and regulates it to the module supply through an AMS1117-3.3V.

The module supports master/slave role switching. Users can exchange data with an external MCU over UART, and in configuration mode can modify the device name, baud rate, advertising, UUID, MTU, MAC binding and power-related parameters. By default the module works in slave role with advertising enabled, UART 19200bps, no parity and 1 stop bit — suitable for smart home, industrial telemetry, automated data acquisition, wearables and BLE human-machine interaction scenarios.

• Supports the BLE 5.1 standard and is compatible with common BLE Central devices.

• Supports master/slave integration; the master can connect to up to 2 slave modules.

• Supports UART transparent transmission, default 19200bps, 8N1.

• Supports low-power sleep, UART wake-up, data-valid indication and connection-status indication.

• Supports 16-bit / 128-bit UUID, MTU 20~128 bytes, Beacon / iBeacon advertising and Bluetooth sniffing.

• Comes with an on-board PCB antenna; module size approx. 14.6mm × 21.9mm.

Main Chip Introduction

This module adopts the E104-BT02 BLE serial communication module design with the Dialog DA14580 as the core solution. The module already integrates RF, protocol stack and serial transparent transmission internally, so the external host MCU does not need to configure the DA14580 registers directly — it only needs to control the MODE, WKP, RESET_H and UART interfaces per this manual.

Chip Overview

The DA14580 is an SoC solution for low-power Bluetooth applications. The E104-BT02 builds on it by integrating BLE protocol processing, UART transparent transmission and parameter storage. The official product datasheet describes the current module as BLE 5.1; early Specification summaries still state BLE 4.2, so both the module firmware version should be recorded for certification, interoperability and production traceability.

Pin Definition

The E104-BT02 is a 20-pin, 1.27mm-pitch SMD module. The table below is compiled from the official product datasheet. Keep the reserved pins P01, P02, P07, P10, P12, P13 and P15 unconnected to external logic.

Functional Block Diagram

The official documentation does not provide a detailed internal block diagram of the DA14580. Combining the external functions of the E104-BT02, the module can be abstracted as the data path "UART interface → module firmware → BLE protocol stack / GATT → RF antenna". P00/MOD, P06/WKP, RESET_H and P14 handle module state, wake-up, reset and role initialization, while P03/APP and P11/STA provide status outputs.

Performance Parameters

The main performance parameters of the E104-BT02 are listed below; values are from the official E104-BT02 product datasheet. Typical values are affected by advertising, connection, LED load, power supply and PCB layout.

Reference Circuit

The reference circuit of the carrier board in this project consists of +5V input, 3.3V regulation, power filtering, the E104-BT02 module, UART / wake-up interface, MODE control, connection-status LED and power LED.

 5V-to-3.3V Power Conversion

U2 uses an AMS1117-3.3V to convert the carrier-board +5V input to the +3.3V required by the module. C1 and C2 provide input/output filtering and module supply decoupling. When designing, check the regulator dropout, heating and power-on overshoot to ensure the module VCC never exceeds 3.6V.

 E104-BT02 Module Section

The E104-BT02 is the core functional device: VCC connects to +3.3V, GND to system ground; P04 / P05 handle UART, P06 is wake-up, P00 is mode control, and P11 outputs connection status. Reserved pins are left floating per the official pin definition.

Buttons and Indicator LEDs

In the schematic, LED1 indicates +5V power and LED2, driven by the P11 net, indicates the Bluetooth connection state. The MODE-related button or interface pulls P00 low to enter AT configuration and resumes transparent transmission when released. LED current should be included in low-power measurements.

 External Interface

The schematic labels CN1 as a 4-pin connector with nets +5V, P06, MTX and MRX; H1 is the MODE-related interface / button connection. Before mass production, add Pin1 orientation and wiring order to the PCB silkscreen and assembly drawings to avoid connector direction errors.

Chip Configuration

The E104-BT02 is a plug-and-play module; there is no need to configure DA14580 registers externally. All common settings are configured via UART AT commands and saved to the module after successful configuration. Before executing AT commands, the module must be awake and P00/MOD must be pulled low.

Communication Interface and Related Protocols

Serial Transparent Transmission Principle

The internal E104-BT02 acts as the core: it wraps the data stream sent by the external MCU over UART into BLE data for wireless transmission, and restores BLE-received data into a UART data stream output to the MCU. The module does not parse user data content — it only performs the bidirectional transparent conversion of "serial electrical signal → BLE wireless data → serial electrical signal".

 AT Commands

AT commands uniformly use the <command> format without appending CR, LF or CRLF. Common commands in configuration mode:

Command differences: The AT manual, product datasheet and early Specification files come from different historical versions. Before importing into software, rely on the actual firmware echo and record the firmware version and any abnormal returns.

PCB Layout Guidelines

• Keep the area under and around the on-board antenna clear per official recommendations: no copper pour, no traces.

• Place the antenna tip near the carrier-board edge and avoid metal enclosures, batteries, screws, shields and high-speed digital lines nearby.

• Provide multi-point ground return for the module GND; place the supply filter capacitor close to VCC / GND; do not route UART or LED lines through the antenna area.

• After changing module orientation, antenna clearance, enclosure material or grounding structure, re-test range, RSSI, throughput and reconnection.

Circuit Engineering & Module Usage

Circuit Source Project

To obtain the circuit source project, follow the official WeChat account 【Freak 嵌入式】.

Module Usage

This module requires attention to three things at the same time: UART direction, MODE configuration level and WKP wake-up state. Recommended hardware connections:

The verified RP2040 wiring uses UART0: GP16 TX → carrier MTX/TX → E104 P05 RX; E104 P04 TX → carrier MRX/RX → GP17 RX. GP16 / GP17 here are only test connections, not mandatory GPIO assignments of the driver.

Important note: The carrier-board net names in this project use host-perspective naming: the MTX/TX net connects to module P05 (module RX), and the MRX/RX net connects to module P04 (module TX). Follow the actual schematic nets — do not cross-connect based on names alone.

Connect the module to the GraftPort-RP2040 development board's UART0 interface using an HY2.0-4P cable:

Application Experiments

The following uses a Raspberry Pi Pico / RP2040, MicroPython and a phone BLE Central as an example to complete AT queries and bidirectional BLE/UART transparent transmission. Before the experiment, confirm the module is powered correctly, the host and module share a common ground, and prepare a connection that can control P00/MOD.

Search for the driver package e104bt02_driver on uPyPI (https://upypi.net/zh/ ), copy the local install command, and import the module driver library via the mip tool:

mpremote mip install https://upypi.net/pkgs/e104bt02_driver/1.3.1

After importing the EBYTE E104-BT02 serial-to-BLE module driver code, copy the main.py code  into your project:

Flash the code, open a terminal, connect to the host with the mpremote tool and run main.py:

1. Keep P06/WKP in the awake state.

2. Hold MODE so P00/MOD is low.

3. Read the module baud rate, name, state, MTU, role and MAC address.

4. Release MODE so P00/MOD returns high.

5. Open the WeChat mini-program (Bluetooth Serial — Jiangxie Tech / 江协科技).

6. Use the Bluetooth assistant to connect to the E104-BT02.

7. Set the receive and send UUIDs (e.g. FFF1 Notify / FFF2 Write).

8. Observe both ends working.

Driver

• Driver library: e104bt02_driver (v1.3.1)

• Install command: mpremote mip install https://upypi.net/pkgs/e104bt02_driver/1.3.1

• For more content, see the original article: Feishu Wiki