The HC-05 Bluetooth wireless serial module is a classic Bluetooth (BR/EDR) transceiver designed to replace a wired UART cable with a short-range wireless link. It is commonly used for Bluetooth SPP (Serial Port Profile) style communication, allowing microcontrollers and embedded systems to transmit and receive serial data as if connected by a direct TTL UART connection. This version includes a 6-pin TTL-to-UART adapter backplane, making it easier to power the module and connect RX/TX lines using standard headers, breadboards, or Dupont jumpers.
The HC-05 Bluetooth wireless serial module is a classic Bluetooth (BR/EDR) transceiver designed to replace a wired UART cable with a short-range wireless link. It is commonly used for Bluetooth SPP (Serial Port Profile) style communication, allowing microcontrollers and embedded systems to transmit and receive serial data as if connected by a direct TTL UART connection. This version includes a 6-pin TTL-to-UART adapter backplane, making it easier to power the module and connect RX/TX lines using standard headers, breadboards, or Dupont jumpers.
HC-05 modules are widely used in prototyping and production-like DIY builds because they provide a simple UART interface while handling Bluetooth pairing and link management internally. Depending on the module revision and firmware, the HC-05 can typically operate in Slave mode (accepting connections from a phone/PC) and may also support Master mode (initiating a connection to another Bluetooth device). Configuration is generally performed through AT commands over the serial interface. How you enter AT mode (button/KEY pin behavior, power-up sequence, and baud rate used for AT commands) can vary by module revision, so it is important to confirm the correct procedure for your specific board.
The included backplane/adapter board is intended to simplify integration by providing a stable power input range and a convenient 6-pin header breakout. Many adapter boards include onboard regulation and level-conditioning features, but the exact electrical behavior (including whether RX is 3.3V tolerant only, whether a divider is present, and the regulator type) varies by manufacturer. For best reliability, treat the UART logic as 3.3V-level unless your specific module documentation confirms 5V-tolerant inputs. When interfacing with 5V microcontrollers, a simple resistor divider or level shifter on the module RX line is a common best practice if the board does not already include it.
1) Power: Supply the adapter board within 3.3V–6V as specified. If powering from a noisy source (motors/servos), add local decoupling near the module and keep power wiring short.
2) UART wiring: Cross-connect TX to RX and RX to TX, and share a common ground. Confirm the module’s UART voltage requirements; if your MCU uses 5V UART and the module RX is not 5V tolerant, use a level shifter or resistor divider.
3) AT configuration: Enter AT mode using the method required by your board revision (often involving a KEY/EN pin or a button during power-up). Use the correct AT baud rate for your firmware.
4) ESP32 note: ESP32 UART is 3.3V logic, which typically matches HC-05 UART levels well. Choose a free hardware UART or remap pins as needed.
5) Mounting and RF: Keep the antenna area clear of metal and high-current traces for better link stability. Orientation and enclosure materials can affect range.
HC-05 Bluetooth module with 6-pin TTL UART backplane
Honest takes from buyers who built with this part.
Ask anything — the team and other customers will reply.
