1. Introduction
The KCX_BT_EMITTER module is a versatile wireless Bluetooth audio transceiver designed for both transmitting and receiving stereo audio. It incorporates Bluetooth 5.3 protocol, ensuring stable connections and supporting automatic reconnection to previously paired devices. The module offers advanced configuration options via serial AT commands, allowing users to customize device names, manage connections, and more. Its operational mode (transmit or receive) is easily configurable using short-circuit solder joints. Integrated indicator lights provide clear status feedback, and it supports connection status level output. This module is ideal for a wide range of applications including Bluetooth audio reception, transmission, and DIY audio projects.
2. Specifications
| Parameter | Value |
|---|---|
| Product Model | KCX_EMITTER |
| Bluetooth Name | Bluetooth Audio |
| Dimensions | 23.30 x 15.20 mm |
| Product Weight | 1.50 g |
| Working Voltage | 3.5-5V |
| Working Current | 35mA |
| Launch Distance | ≤ 20 meters |
| RF Output Power | +5dbm |
| RF Frequency Range | 2402-2480MHz |
| Audio Dynamic Range | 80dB |
| Total Harmonic Distortion of Audio | -70dB |
| Audio Frequency Response | 20Hz-20KHz |
| Audio Signal-to-Noise Ratio | 95dB |
| Audio Input/Output Signal Amplitude | ≤ 2Vpp |
| Number of Channels | 2 channels (stereo) |
| Transmission Delay | 250-300ms |
3. Product Overview
The module features a compact design with clearly labeled components and pinouts for easy integration.
Module Components:
- Onboard Bluetooth antenna
- IPX1 external 2.4G antenna interface
- High quality crystal oscillator
- Dual color LED status indicator light
- PCB antenna with breakable design
- Bluetooth pairing button
- Bluetooth 5.3 chip
- Send/receive mode setting solder joints
- 11PIN 1.25mm spacing, patch stamp hole
Pinout Description:
| Pin Number | Pin Name | Function Description |
|---|---|---|
| 1 | +5V | 3.5-5V power supply pin |
| 2 | PGND | Power Ground |
| 3 | LINK | Connection status pin (Bluetooth with connection output 3.3V, no connection output 0V) |
| 4 | RX | Serial port receiver (extended function pin, used for configuring Bluetooth related information on the serial port) |
| 5 | TX | Serial port sender (extended function pin, used for configuring Bluetooth related information on the serial port) |
| 6 | AUDIO_L | Input audio signal (transmit mode) / Output audio signal (receive mode) |
| 7 | AUDIO_R | Audio signal right channel input (transmit mode) / output (receive mode) |
| 8 | AGND | Audio Ground |
| 9 | DP | USBDM data cable interface (used to connect computer USB as a sound card) |
| 10 | DM | USBDM data cable interface (used to connect computer USB as a sound card) |
| 11 | CONNECT | External connection pairing button port (same as module connection pairing button function) |
4. Setup and Installation
4.1 Transmission/Reception Mode Settings
The module's operational mode (Bluetooth transmit or receive) is determined by the state of the RX/TX solder joints. By default, the module is in transmit mode (solder joints not connected). To switch to receive mode, connect the RX/TX solder joints.
4.2 Connection Methods
Connection Method 1: Analog Audio Input/Output
This circuit is suitable for both transmission and reception modes. In transmit mode, audio signals from devices like mobile phones, computers, or MP3/4 players are input via AUDIO_L/AUDIO_R. In receive mode, the module outputs audio signals via AUDIO_L/AUDIO_R, which can drive headphones or be connected to an amplifier.
Important Notes for Analog Audio Connection:
- A 10V/100uF filtering capacitor must be connected at the module's power supply end (+5V and PGND) for filtering. Position it as close as possible to these ports.
- The AGND (Audio Ground) pin requires an independent connection to the negative terminal of the power supply (e.g., battery negative, 5V regulated power supply negative). This ensures the analog audio circuit's ground is stable and not affected by other signals. Do not leave it suspended or disconnected.
- Ensure the 5V power supply has minimal ripple. Noisy power supplies (e.g., some mobile phone chargers or power banks) can introduce noise into the audio output.
Connection Method 2: USB Audio Input (Transmit Mode Only)
This method is exclusively for transmit mode. When the module is successfully connected via Bluetooth to a receiving device, connecting the module to a computer via its USB data interface (DP/DM pins) will cause the computer to recognize it as a 'USBAudio2.0' sound card. Audio played on the computer will then be wirelessly transmitted to the Bluetooth receiving module.
4.3 External 2.4G Antenna Instructions
The module includes an IPX1 RF output interface for connecting an external 2.4G antenna. An external antenna is necessary when the module is integrated into metal enclosures. To use an external antenna, you must break the onboard PCB antenna and then plug an IPX RF cable into the IPX interface. The external 2.4G antenna and IPX cable are not included with the module and must be provided separately.
5. Operating Instructions
5.1 Status Indicator Lights
The module features a dual-color LED (red and blue) to indicate its status:
Transmit Mode (Red LED active):
- Bluetooth not connected: The red light flashes uniformly.
- Bluetooth connection successful: The red light flashes twice every 5 seconds.
Receive Mode (Blue LED active):
- Bluetooth not connected: The blue light flashes uniformly.
- Bluetooth connection successful: The blue light flashes twice every 5 seconds.
5.2 Button Function Description
A single button on the module controls Bluetooth connection pairing and audio input switching:
- Short press: Disconnects the current Bluetooth connection and initiates re-pairing with a new device.
- Long press (2 seconds): Switches between line audio input and USB audio input. This function is only active when USB audio is connected and online.
5.3 Application Scenarios
Scenario 1: Mobile Phone to Wireless Headset/Speaker
Scenario 2: Computer to Wireless Headset/Speaker
6. Troubleshooting
If you encounter any issues, particularly with audio noise, please review the following common causes:
- Audio Noise: Modules typically do not generate noise inherently. If noise is present in the audio output, check your power supply and grounding:
- Power Supply Filtering: Ensure the 10V/100uF filtering capacitor is correctly installed and positioned as close as possible to the +5V and PGND pins of the module.
- Audio Ground (AGND): Verify that the AGND pin is independently connected to the negative terminal of your power supply. It should not be left floating or connected to other signal grounds, as this can introduce interference.
- Power Supply Ripple: Use a clean, stable 5V power supply with minimal ripple. Noisy power sources, such as some mobile phone chargers or power banks, can directly impact audio quality.
7. User Tips
No specific user tips were available from provided reviews or Q&A content.
8. Warranty and Support
For warranty information and technical support, please contact the seller directly. Keep your purchase records for reference.
9. Compliance and Safety Warnings
⚠ WARNING: This product can expose you to chemicals including lead, which is known to the State of California to cause cancer and birth defects or other reproductive harm. For more information go to www.P65Warnings.ca.gov.
