JDY-31 SPP-C Bluetooth Serial Pass-Through Module User Manual

1. Product Overview

The JDY-31 SPP-C Bluetooth Serial Pass-Through Module is designed for wireless serial communication, offering a reliable and efficient solution for various embedded systems and IoT applications. It functions as a Bluetooth 3.0 SPP (Serial Port Profile) module, enabling seamless data transmission between devices. This module is a suitable replacement for HC-05 and HC-06 modules, providing stable performance for projects requiring Bluetooth connectivity.

Figure 1: Two JDY-31 SPP-C Bluetooth modules, showcasing their compact design and pin headers.

2. Key Features and Specifications

The JDY-31 module boasts several features making it ideal for serial communication:

• Working Frequency: 2.4GHZ
• Communication Interface: UART
• Bluetooth Version: Bluetooth 3.0 SPP
• Working Voltage: 1.8-3.6V (3.3V recommended)
• Transmitting Power: 8db (max)
• Receiving Sensitivity: -97dbm
• Transmission Distance: Up to 30 meters (open area)
• Antenna: Built-in PCB antenna
• Master-Slave Support: Slave mode only
• Unconnected Working Current: 4.7mA
• Current After BLE Connection: 7.3mA
• SPP Maximum Throughput: 16K bytes/s
• Working Temperature: -400C to 800C

Detailed Specifications:

Figure 2: A JDY-31 SPP-C Bluetooth module with dimensions indicated, showing its length of 37.4mm and width of 15.9mm.

3. Setup and Connections

Proper connection of the JDY-31 module is crucial for its functionality. The module features several pins for power, data, and control.

Figure 3: Bottom view of the JDY-31 SPP-C module, clearly labeling the pin functions: LEVEL (3.3V), STATE, RXD, TXD, GND, VCC, and EN, along with power input range (3.6V-6V).

Pin Descriptions:

• VCC: Power supply input. Recommended 3.3V, but supports 1.8V to 3.6V. The module has an onboard regulator for 3.6V-6V input.
• GND: Ground connection.
• TXD: Transmit Data. Connects to the RXD pin of your microcontroller/device.
• RXD: Receive Data. Connects to the TXD pin of your microcontroller/device.
• EN: Enable pin. Pull high to enable the module.
• STATE: Status indicator pin. Typically goes high when connected to another Bluetooth device.
• LEVEL: Voltage level selection for UART. Indicates 3.3V logic level.

Basic Connection Steps:

1. Connect VCC to your power supply (e.g., 3.3V or 5V, ensuring it's within the 1.8V-6V range).
2. Connect GND to the ground of your power supply and microcontroller.
3. Connect TXD of the JDY-31 to RXD of your microcontroller.
4. Connect RXD of the JDY-31 to TXD of your microcontroller.
5. Ensure the EN pin is pulled high (connected to VCC) for the module to operate.

Note: When connecting to 5V microcontrollers, ensure proper voltage level shifting for TXD/RXD if the microcontroller is not 5V tolerant on its RX pin, as the JDY-31 operates at 3.3V logic levels.

4. Operating Instructions

The JDY-31 module operates as a Bluetooth SPP slave device, meaning it can be discovered and connected to by a Bluetooth master device (e.g., a smartphone, computer, or another Bluetooth module configured as master). Data is then transmitted transparently over the serial port.

Pairing and Connection:

1. Power on the JDY-31 module. The STATE pin will typically be low or blinking, indicating it's discoverable.
2. On your master device (e.g., smartphone), scan for Bluetooth devices. The JDY-31 module will usually appear as "JDY-31" or a similar name.
3. Select the JDY-31 module to pair. The default pairing code is typically "1234" or "0000".
4. Once paired and connected, the STATE pin on the JDY-31 module will usually go high, indicating an active connection.

Serial Data Transmission:

After a successful connection, any data sent to the JDY-31's RXD pin will be transmitted wirelessly to the connected master device. Conversely, any data received wirelessly from the master device will be outputted through the JDY-31's TXD pin.

The module can be configured using AT commands sent via the serial port before a Bluetooth connection is established. Common AT commands allow setting the module's name, baud rate, and pairing code. Refer to the specific JDY-31 AT command set documentation for detailed configuration options.

Figure 4: Top view of a single JDY-31 SPP-C Bluetooth module, highlighting the main chip and antenna.

5. Maintenance

The JDY-31 module is a robust electronic component, but proper handling and care can extend its lifespan and ensure reliable operation:

• Handle with Care: Avoid dropping or subjecting the module to physical shock.
• Static Electricity: Always handle the module in an ESD-safe environment to prevent damage from static discharge.
• Environmental Conditions: Operate and store the module within its specified temperature range (-400C to 800C) and avoid high humidity or corrosive environments.
• Power Supply: Ensure the power supply voltage is stable and within the recommended range (1.8V-3.6V, or 3.6V-6V if using the onboard regulator) to prevent damage.
• Cleaning: If necessary, gently clean the module with a soft, dry cloth. Avoid using liquids or harsh chemicals.

6. Troubleshooting

If you encounter issues with your JDY-31 module, consider the following troubleshooting steps:

• Module Not Powering On:
  • Verify VCC and GND connections are correct and stable.
  • Ensure the power supply voltage is within the specified range.
• Module Not Discoverable:
  • Confirm the EN pin is pulled high.
  • Check if the module is already connected to another device. The JDY-31 is a slave module and can only connect to one master at a time.
  • Ensure the module is powered correctly.
• Cannot Pair/Connect:
  • Double-check the pairing code (default is usually "1234" or "0000").
  • Ensure the master device's Bluetooth is enabled and functioning correctly.
  • Try restarting both the module and the master device.
• No Data Transmission:
  • Verify TXD and RXD connections are correctly cross-connected (TXD to RXD, RXD to TXD).
  • Ensure the UART baud rates on both the module and your microcontroller/device match.
  • Check if the module is actively connected (STATE pin high).
  • Confirm that the serial port on your microcontroller is correctly initialized and sending/receiving data.
• Intermittent Connection/Data Loss:
  • Check for interference from other 2.4GHz devices.
  • Ensure the transmission distance is within the 30-meter limit and there are no significant obstacles.
  • Verify power supply stability.

7. Warranty and Support

For specific warranty information, please refer to the purchase documentation or contact the seller directly. As a general guideline, electronic components typically come with a limited warranty against manufacturing defects.

For technical support or further assistance, please reach out to the manufacturer or the vendor from whom you purchased the JDY-31 SPP-C Bluetooth Serial Pass-Through Module. Provide your product model and a detailed description of the issue to facilitate a quicker resolution.