HC-04 Bluetooth Module [Original]

SKU: FA2039-4
Bluetooth Protocol

Bluetooth V2.0 + EDR (Classic)
Operating Voltage

3.6V – 6.0V DC
Operating Current

~35mA (Pairing); < 10mA (Connected)
Logic Level (I/O)

3.3V TTL (VCC is 5V compatible)
Communication Interface

UART (Universal Asynchronous Receiver/Transmitter)
Default Baud Rate

9600 bps
Default Pairing PIN

1234
Frequency Band

2.4GHz ISM Band
Range

~10 Meters (Class 2)
Operating Temperature

-25°C to +75°C
Product Description
The Original HC-04 is a high-stability Bluetooth 2.0+EDR (Enhanced Data Rate) serial communication module designed for industrial-grade wireless data transmission. While it shares many similarities with the HC-06, the HC-04 is specifically engineered with an original chipset that offers superior frequency consistency and lower packet loss in environments with high electromagnetic interference.
This module acts as a “Slave-only” wireless serial bridge. It is designed to be discovered and connected to by “Master” devices such as Android smartphones, tablets, or PCs. Once a connection is established, the HC-04 provides a Transparent Data Pipe; any serial data (TTL) sent to the module’s RX pin is instantly transmitted over the air, appearing at the paired device’s terminal. It is the perfect solution for developers who require a robust, reliable, and “no-configuration” wireless link for their hardware.
Key Features
  • Original Industrial Chipset: Features genuine silicon for better long-term reliability and more consistent pairing compared to generic alternatives.
  • Plug-and-Play Slave Mode: Pre-configured as a Slave device, making it instantly discoverable by any Bluetooth Master (Phone/PC) without needing initial setup.
  • Transparent Serial Link: Requires no knowledge of complex Bluetooth stacks; it functions exactly like a wireless RS232 serial cable.
  • Built-in Logic Protection: The 6-pin breakout board includes a power regulator supporting 3.6V to 6.0V, ensuring compatibility with standard 5V and 3.3V power rails.
  • High-Speed Response: Optimized for low-latency data transmission, ideal for real-time sensor monitoring and remote control applications.
  • Diagnostic LED: The onboard LED indicates pairing status: fast blinking (unpaired/searching) and steady light (paired/connected).
Usage Scenarios
  • Single User / Hobbyist: Wireless control for Arduino/Raspberry Pi robots, DIY smart home sensors, and remote PC hardware monitoring.
  • Business / Industrial: Wireless serial debugging for CNC machinery, point-of-sale (POS) terminal communication, wireless data collection for medical devices, and industrial PLC programming.
Q: Can I use the HC-04 with an iPhone?

No. The HC-04 uses Bluetooth Classic (2.0). Apple iOS devices only support “Bluetooth Low Energy” (BLE 4.0+) for serial profiles. This module is fully compatible with Android, Windows, macOS, and Linux

Q: What is the difference between the HC-04 and the HC-05?

The HC-05 can be both a Master and a Slave. The HC-04 is a Slave-only module. Use the HC-04 when your device only needs to be “found” and connected to by a phone or computer

Q: How do I change the Baud Rate or Name?

You can change these settings using AT Commands while the module is not connected to a Bluetooth device. Simply send commands like AT+NAME=MyDevice or AT+BAUD4 (for 9600) via a serial monitor.

Q: Is it safe to connect the RX pin directly to a 5V Arduino?

While the power pin (VCC) is 5V compatible, the data pins are 3.3V logic. For industrial-level reliability, we recommend using a voltage divider (1kΩ and 2kΩ resistors) on the RX line of the HC-04 to protect the chip from 5V signals.

Q: Does it support audio or music streaming?

No. The HC-04 is strictly a Data Module meant for serial text and sensor information. It does not support A2DP or other audio profiles

Q: Will it remember my custom settings after power-off?

Yes. Any changes made to the Name, PIN, or Baud Rate via AT commands are stored in the onboard non-volatile Flash memory

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