IRXON BT578 V3 RS232 Bluetooth Adapter

1. Introduction

Thank you for purchasing the BT578_V3 Serial Bluetooth adapter! This adapter is typically connected to an RS232 serial communication device via its DB9 serial port and then linked to a computer or mobile phone via Bluetooth SPP or BLE. This creates a wireless bridge between the serial device and the computer or mobile phone, eliminating the need for conventional RS232 serial cables and providing a wireless serial connection with greater freedom and convenience.

Diagram: Conventional vs. Wireless Serial Connection

Conventional Serial Connection: A "Desktop or laptop computer" is shown connected via a "RS232 serial cable" (with TX and RX lines indicated) to a "Serial Device".

Upgrade to wireless RS232 communication: A "Bluetooth enabled desktop or laptop, Android, iOS mobile phone and tablet" establishes a wireless connection (represented by Wi-Fi/Bluetooth symbols) to the "BT578 Bluetooth Serial Adapter". The adapter then connects to a "Serial Device" via TX and RX lines, forming a wireless bridge.

1.1 Features

• Supports Classic Serial Port Profile (SPP) and new generation Bluetooth LE (BLE).
• Utilizes the popular USB Type-C connector for power supply or charging.
• AT commands can be sent via Bluetooth link to personalize settings like name and baud rate.
• A green LED indicates TX/RX activity of the RS232 serial communication.
• Supports Pin 9 power supply; connect pin 9 to 5V and pin 5 to GND.
• Built-in battery and charging circuit, offering more than 40 hours of battery usage time.
• Can connect to female or male serial devices using the DB9 connector or a converter.

1.2 Package Contents

• BT578_V3 Serial Bluetooth adapter x1
• DB9 male to female converter (Gender Changer) x1
• USB to Type-C power/charging cable x1
• This User Guide (Electronic edition)

2. Specifications

2.1 Technical Specifications

• Standard: Bluetooth V3.0 (SPP) + Bluetooth V4.2 (BLE)
• Selectable Serial Baud Rate: 1200, 2400, 4800, 9600, 19200, 38400, 57600, 115200 bps
• Serial Communication BLE Characteristic: 0000ffe1-0000-1000-8000-00805f9b34fb
• Typical Wireless Connection Distance: 30 meters (line of sight)
• TX Power: 5dBm
• RX Sensitivity: -95dBm
• Typical Working Current: 8 mA
• Dimension and Weight: 78x34x16mm, 30g

2.2 RS232 Interface

The document shows two types of DB9 connectors used for RS232 serial communication:

• DB9-M (Male): A 9-pin male connector with pins labeled 1, 5, 6, 9.
• DB9-F (Female): A 9-pin female connector with pins labeled 5, 1, 9, 6.

A table details the pin assignments:

Pins 1, 4, 6, 7, 8 are noted as "No connection". The VCC Range is 4V-6V.

2.3 Factory Settings

The default factory settings of BT578_V3 are:

• RS232 Serial Port Baud Rate: 9600bps
• RS232 Serial Port Parity: None
• RS232 Serial Port Data bit: 8
• RS232 Serial Port Stop bit: 1
• RS232 Serial Port Flow Control: None
• Bluetooth Name: BT578_SPP_xxxx (where xxxx are the last 4 digits of the BD address)
• Bluetooth Name: BT578_BLE_xxxx (where xxxx are the last 4 digits of the BD address)
• Bluetooth SPP Pairing Password: 1234

3. Description

Please refer to the hardware structure diagram on the first page for visual reference.

3.1 Wake-up Button

This button is used in conjunction with the "AT+SLEEP" command. Sending the sleep command puts the adapter into a sleep state. Pressing the button then wakes the adapter up.

3.2 Power Supply

• Internal lithium battery power supply: With the Type-C cable disconnected, slide the internal battery power switch towards the serial port direction. The adapter will draw power from the internal battery. Slide it to the other side to shut down the adapter.
• External USB power supply: Slide the internal battery power switch away from the serial port direction. Connect the Type-C cable to a USB power source. The red LED will turn on, indicating the adapter is powered by the external supply. The internal battery charges when the adapter is connected to external power via the Type-C cable. The red LED will turn off once the battery is fully charged.
• Pin 9 of DB9 connector power supply: Connect pin 9 to a 4~6V source and pin 5 to GND.

3.3 LED Indicators

• Power/Charging LED (Red) ?: This LED is lit when external power is connected. It also functions as a charging indicator. When the internal battery is fully charged, the LED will blink or turn off. Charging time from empty to full is approximately 1 hour.
• Bluetooth Status LED (Blue) ?: The blue LED blinks to indicate that Bluetooth is broadcasting and the adapter is waiting for a Bluetooth search and connection. This mode is also used for sending serial AT commands. When the LED is constantly lit, it signifies that Bluetooth is connected to a computer or mobile phone, and the adapter is ready for AT commands and Bluetooth communication.
• Serial Data Activity LED (Green) ?: This green LED flashes to indicate when bytes are being sent or received through the BT578 serial port.

3.4 DB9 Male/Female Slide Switch

• The BT578 has a DB9 male serial interface. It can be directly connected to commonly used female DB9 serial devices. In this case, the switch should be slid to the "M" side.
• To connect the BT578 to a male DB9 serial device, use the provided DB9 gender changer. In this scenario, the switch should be slid to the "F" side.

4. Configuration

AT commands are used to query or change settings, such as the serial baud rate of the BT578 adapter. You can send AT commands via either a Bluetooth connection or a serial connection.

4.1 Sending AT Commands via Bluetooth Connection

It is recommended to use an Android phone with an app to connect to the BLE name of BT578_V3 and send AT commands. Several suitable apps are available; "Serial Bluetooth Terminal" is recommended and can be installed from Google Play. After installation, open the app, select "Devices", click "SCAN" in the "Bluetooth LE" column, and then select "BT578_BLE_xxxx" from the scan results to connect to the BT578. On the subsequent "Terminal" interface, you can send AT commands. The app's operation interface is illustrated in the provided figure.

Android App Interface: A screenshot from an Android application named "Serial Bluetooth Terminal". It shows a list of Bluetooth LE devices, including "BT578_BLE_7700", and a terminal screen displaying AT commands like +BAUD=8, AT+NAME, +NAME=BT578_SPP_7700, AT+PIN, +PIN=1234, AT+LADDR, and AT+BAUD.

4.2 Sending AT Commands via Serial Connection

Connect the adapter to the RS232 port of a Windows computer using the DB9 gender changer, sliding the Male/Female switch to the "F" side. If your computer lacks an RS232 port, you will need a USB-to-RS232 serial cable to add a COM port. Download the "BT578 Tester" program from http://www.irxon.com/download/BT578-Tester.rar. Extract the RAR file to obtain an executable file. Run the program, select the COM port number to which the BT578 is connected, and set the baud rate and other parameters to match the BT578 adapter's serial settings (factory default: 9600, 8, 1, N). Check "new line" to append a carriage return and line feed to AT commands. Click "OpenCom" to open the serial port. Type "AT" twice in the data sending area and click "Send". If "+OK" is returned in the data receiving area, the test command was successful, and you can proceed with other AT commands. The program's interface is shown in the figure.

Windows Software Interface: A screenshot of the "BT578 Tester" program on a Windows PC. It displays sections for "Computer COM Port Setting Area" (showing COM20, BaudRate 9600, DataBit 8, StopBit 1, Flow Control None), "Data Sending Area" (where "AT" commands are typed and sent), "Data Receiving Area" (showing responses like "+OK"), and "User Preset Commands or Data".

4.3 AT Commands

AT commands must be in uppercase English letters. The "+" character is also English. Each AT command must be terminated by a Carriage Return (CR, Hex:0D) and a Line Feed (LF, Hex:0A).

Query/Change Adapter's Serial Baud Rate

• Querying command: AT+BAUD. Return message example: +BAUD=4
• Changing command: AT+BAUDn, where "n" is the code for the desired baud rate. Refer to the table below.

For example, sending AT+BAUD8 will change the baud rate to 115200 bps. The new baud rate takes effect immediately. Update your computer's baud rate accordingly if sending serial AT commands.

Query/Change SPP Broadcast Name

• Querying command: AT+NAME. Return message example: +NAME=BT578_SPP_01A8
• Changing command: AT+NAMESPPname. Return message: +OK

The SPP name can consist of letters, numbers, dashes, or slashes, and must not exceed 18 characters.

Query/Change BLE Broadcast Name

• Querying command: AT+NAMB. Return message example: +NAMB=BT578_BLE_01A8
• Changing command: AT+NAMBBLEname. Return message: +OK

The BLE name can consist of letters, numbers, dashes, or slashes, and must not exceed 18 characters.

Query/Change Bluetooth SPP Pairing Password

• Querying command: AT+PIN. Return message example: +PIN=1234
• Changing command: AT+PINpassword. Return message: +OK

The password is fixed at 4 digits and can be composed of letters or numbers. The factory default is 1234. (Password is not required for BLE connections).

Query Bluetooth Address of Adapter

• Command: AT+LADDR. Return message example: +LADDR=36630D0401A8

Query/Change Adapter's Serial Parity

• Querying command: AT+UARTMODE. Return message example: +UARTMODE=0,0
• Changing command: AT+UARTMODEm,n. Code 'm' is fixed to 0. Code 'n' represents the parity mode:
  • n=0: None (no parity, factory default)
  • n=1: Odd (odd parity)
  • n=2: Even (even parity)

For example, sending AT+UARTMODE0,2 will change the parity mode to even. After changing the parity mode, the adapter will restart automatically.

Restart Adapter

• Command: AT+RESET. It is recommended to restart the adapter after making AT command settings.

5. Application

The adapter is typically connected to a serial device via its DB9 port and communicates with a mobile phone or computer using Bluetooth SPP or BLE, thereby establishing a wireless serial connection between the serial device and the mobile phone or computer.

5.1 Preparation

RS232 serial communication requires both sides to have identical serial settings. For the serial device to which the BT578 adapter will be attached, consult its manual to determine its serial settings. The default settings for the BT578 serial port are 9600, N, 8, 1. If these differ from the serial device's settings, refer to section 4.3 to adjust them so both sides match.

Connect the adapter to the serial device using the DB9 connector. If the device's DB9 port is male, use the Gender Changer and slide the M/F switch to the "F" side. Turn on the adapter's power and wait for Bluetooth searching and connecting.

The BT578_V3 can connect to a computer or Android device via Bluetooth SPP, or to an Android or iOS device via Bluetooth LE. (SPP and BLE connections cannot be active simultaneously on the BT578 adapter).

5.2 Communicate with Computer via SPP

On a laptop or desktop computer, search for Bluetooth devices and select "BT578_SPP" from the list (do not select "BT578_BLE"). Send a pairing request from the computer and enter the BT578 pairing password (default is 1234). After pairing, check "Device Manager" on the computer; the system will have assigned a Bluetooth virtual COM port to the adapter. In your serial device application program, select the virtual COM port number and open the COM port. A Bluetooth link will be established between the computer and the adapter (the blue LED will turn constant on), enabling communication with the adapter and subsequently with the serial device attached to it.

5.3 Communicate with Android Device via SPP or BLE

Bluetooth SPP is well-supported on Android systems (iOS has limitations), and numerous apps are available. The "Serial Bluetooth Terminal" app is recommended and can be installed from the Google Play store. This app supports both SPP and BLE, making it suitable for connecting the BT578_V3 adapter, which supports dual-mode SPP and BLE. To connect the adapter to an Android device via SPP, first search and pair with "BT578_SPP_xxxx" in the system "Settings" -> "Bluetooth". After pairing, open "Serial Bluetooth Terminal", click "Devices", and select "BT578 SPP" under the "Bluetooth CLASSIC" column to establish an SPP connection. To exit SPP connection, navigate to the "Bluetooth LE" column, click "SCAN", and select "BT578_BLE_xxxx" from the scan list to establish a BLE connection. The adapter's blue LED will remain constantly lit when either an SPP or BLE connection is successfully built, indicating readiness for communication with the adapter and the attached serial device.

5.4 Communicate with iOS Device via BLE

BLE communication is performed by writing to and listening to the Bluetooth characteristic "FFE1" of the adapter. Install an app named "LightBlue" from the App Store. Run the app, select "BT578_BLE_xxxx" from the Bluetooth scan list, click "0xFFE1" on the next interface, check "Listen for notification" to enable data reception, and click "Write new value" to send data to the adapter.

6. FAQ

Q: What is Bluetooth SPP and what is Bluetooth BLE, and what is the difference?

A: Bluetooth SPP is the abbreviation for Serial Port Profile. SPP is a protocol of traditional Bluetooth that can virtualize a Bluetooth link into a serial connection. Bluetooth BLE is the abbreviation for Bluetooth Low Energy. BLE is a newer Bluetooth technology introduced with Bluetooth 4.0. There are several differences between the two protocols:

1. Different user interfaces: The interface provided by SPP is a Bluetooth virtual serial COM port; the interface provided by BLE is a Bluetooth characteristic.
2. Different communication target: SPP is typically used to connect to computers; BLE is usually used to connect to Android or iOS devices.
3. Different applications: Serial device applications can still be used over a Bluetooth SPP connection; however, Bluetooth characteristics provided by BLE often require new application development.

Q: After pairing a Windows computer with BT578_SPP_xxxx, the computer generates two virtual Bluetooth COM ports. Which COM port should be selected in the serial communication application?

A: The "outgoing" COM port should be selected. Click "More Bluetooth Options" in the computer's Bluetooth settings interface, then click "COM Port" in the new window. You will see "outgoing" and "incoming" signs under "Direction". The outgoing port usually has "Dev B" appended to it.

Q: What are the changes in the V2.0 user guides compared to the original version?

A: Since November 2024, newly produced BT578_V3 serial Bluetooth adapters include the function of sending AT commands via Bluetooth connection. The V2.0 user guides have added an introduction to this feature.

For more information, please visit http://www.irxon.com/english/.