Hi-Link HLK-B50 Dual Mode Bluetooth Module User Manual

: June 13, 2024
: Hi-Link

Table of Contents

Shenzhen Hi-Link Electronic Co., Ltd.
HLK-B50

Shenzhen Hi-Link Electronic Co., Ltd.

HLK-B50

Dual Mode Bluetooth Module

User Manual

Terminology, terminology explanation

Name

| Explanatory notes
---|---

Transmission

| Transparent transmission, forwarding data between Bluetooth and serial port as is

Bluetooth

| Bluetooth, a short-range wireless communication technology

BLE

| Bluetooth Low Energy, low Power Bluetooth, a new Bluetooth specification with lower power consumption and longer transmission and communication distances

GATT

| Low Power Bluetooth (BLE) connections are built on the GATT (Generic Attribute Profile) protocol, a common specification for sending and receiving data on top of a Bluetooth connection

Bluetooth Host

| One of the device roles in the Bluetooth connection, the host goes to scan the slave device and initiates the connection to the slave device, etc. Its leading role in the Bluetooth connection

Bluetooth Slave

| One of the device roles in a Bluetooth connection, the slave goes to broadcast its own information and passively waits for a connection

Bluetooth Radio

| Bluetooth slave devices send broadcasts periodically so that the surrounding host devices can scan and recognize themselves, and the host devices can initiate connections to the slaves based on the scanned slave information

Broadcast interval

| Bluetooth slave device to send broadcast interval, the smaller the interval the faster it is scanned but the greater the power consumption, the greater the power consumption is smaller

Connection interval

| After two Bluetooth devices establish a connection, the beat of the transmission data, the smaller the interval, the faster the transmission speed, the smaller the delay, but the greater the power consumption

Pair Binding

| A mechanism for communication security in Bluetooth technology, which is implemented in the Bluetooth link layer

OTA

| Over-the-air upgrade, i.e. firmware upgrade of the module via Bluetooth wireless

Reconnection interval

| When the module is the host, when the Bluetooth connection is not connected or disconnected, how long the interval is automatically reconnected

SPP

| Bluetooth serial protocol, which is a subset of classic Bluetooth

Table 1 Terminology name explanation table

1 Product function introduction

HLK-B50 is a BLE5.0 dual-mode Bluetooth-serial port pass-through module developed and produced by Hi-Link Electronics, which can support both Bluetooth SPP and GATT pass-through, and various devices with serial ports can use Bluetooth wirelessly to send and receive data simply and quickly through this module.

The basic functions and features are as follows :

Built-in 32-bit ARM Cortex M3 core with main frequency up to 48MHz
Fast and stable Bluetooth-serial pass-through with serial baud rate up to 921600
Master-slave Bluetooth BLE 5.0, can be set as master or slave mode, support binding encryption
Dual-mode Bluetooth with data transit via GATT or SPP and simultaneous connectivity
Support A2DP V1.3 and AVRCP V1.6, built-in Audio CODEC
Built-in lithium battery charging circuit, charging current up to 200mA
Built-in LDO, adjustable LDO output voltage
Built-in Watchdog for long and reliable operation
Wide operating voltage 2.6~4.2V, 3.3V typical
Rich output pins (UART, I2C, SPI, GPIO, ADC, PWM, I2S, etc.) for flexible and in-depth hardware and software customization development services

2 Pin definition

Figure 1 Pin location schematic

Pins

| Symbols|

IO types

| Function
---|---|---|---

1

| TX0|

O

| Module pass-through serial output

2

| RX0|

I

| Module pass-through serial input

3

| PC0|

IO

| Reserved function, not used

4

| PC1|

IO

| Reserved function, not used

5

| PC2|

IO

| Reserved function, not used

6

| PC3|

IO

| Reserved function, not used

7

| PC4|

IO

| Reserved function, not used

8

| PC5|

IO

| Reserved function, not used

9

| PC7|

IO

| Function button input, internal pull-up, bottom board connected to ground button
Short press (0.2~3s): enter AT command mode
Long press (8~20s): Restore the default configuration

10

| PC6|

IO

| Reserved function, not used

11

| RESET|

AI

| Reset restart module, active high, not dangling, external 10K pull- down resistor required

12

| VBAT|

PWR

| Power input DC 3.3V, battery powered case connected to the battery

13

| GND|

GND

| Power ground

14

| VCHG|

AI

| Charger input, prohibit use without battery power

15

| TX1|

O

| Burn serial output

16

| RX1|

I

| Burn serial input

17

| PB4|

IO

| Reserved function, not used

18

| PB5|

IO

| Reserved function, not used

19

| MIC_IN|

AI

| Reserved function, not used

20

| MIC_BIAS|

AO

| Reserved function, not used

21

| GND|

GND

| Power ground

22

| GND|

GND

| Power ground

23

| EXT_FLAS|

AO

| Reserved function, not used

24

| SPK_N|

AO

| Reserved function, not used

25

| SPK_P|

AO

| Reserved function, not used

26

| PB3|

IO

| Reserved function, not used

27

| PB2|

IO

| Reserved function, not used

28

| PB1|

IO

| Reserved function, not used

29

| PB0|

IO

| Reserved function, not used

30

| PA3|

IO

| Reserved function, not used

31

| PA2|

IO

| Reserved function, not used

32

| PD7|

IO

| Reserved function, not used

33

| PD6|

IO

| Bluetooth connection status output, high level: not connected, low level: connected

34

| PD6|

IO

| Bluetooth connection status output, high level: not connected, low level: connected

Table 2 Pin definition table

3 Typical application circuits

The following is the basic application circuit reference of this module, for more functions, please refer to the module manual, or contact our engineers for assistance.

Hi-Link HLK-B50 Dual Mode Bluetooth Module - Figure 2 Figure 2 Basic minimum circuit

Note:

RESET pin can not be suspended, need to connect 10K pull-down resistor.
Metal objects will affect the Bluetooth signal transmission and reception, the use of the module should be as far away as possible from metal objects, PCB design requirements of the module

Antenna part of the hollow below can not lay copper.

4 Basic function description

4.1 Transparent transmission principle

HLK-B50 is a cost-effective dual-mode Bluetooth-serial port pass-through module launched by Hi-link Electronics, designed to enable user devices with serial ports only to use Bluetooth for wireless transmission quickly and easily, with serial port pass-through, the user’s product does not need to care about the complex Bluetooth protocol stack and RF circuit, just a simple serial port transceiver, that is, the data can be transmitted directly on the Bluetooth wireless connection.

Transparent transmission is short for transparent transmission, that is, the role of the module is equivalent to the establishment of a transparent transmission pipeline between the serial port and the Bluetooth connection, the data sent by the user in the serial port will be forwarded to the device connected through the Bluetooth, the data sent through the Bluetooth will also be forwarded to the serial port, the whole process of the user does not need to care about the complex Bluetooth connection how to achieve, and HLK-B50 module from the beginning to the end only The HLK-B50 module only carries out the original data handling and forwarding without parsing and processing the data transmitted by the user, so the user can safely and conveniently use this transparent transmission capability.

The principle of Bluetooth-serial pass-through function is shown below, please see <5 Quick Start Guide> for the specific test verification method.

Hi-Link HLK-B50 Dual Mode Bluetooth Module - Figure 3 Figure 3 Schematic diagram of the Bluetooth connection pass- through function

This module supports master and slave when using BLE connection, the module can be set not as a master role or slave role. In the master role, the module can actively connect to other slave devices or modules, and in the slave role, it can be connected by other Bluetooth host devices, including other as the master B50 module.
SPP connection and BLE connection can exist at the same time, the data received by the module serial port will be forwarded to each connected Bluetooth device via Bluetooth, and the data sent by each connected Bluetooth device will also be forwarded to the module serial port.

4.2 Operating modes of the module (pass-through and AT command modes)

The HLK-B50 module has two operating states: pass-through mode and AT command mode.
In AT command mode, you can send AT command to the module through serial port to query and set the parameters of the module.
In the pass-through mode, the module will pass the serial port data and the Bluetooth connection data in both directions.
When the module is started, the default is the pass-through mode. Exiting the pass-through mode to enter AT mode will not affect the Bluetooth connection status, and the serial The data transmission of serial-Bluetooth is suspended and the data received by the serial port is processed by the current AT command; the data transmission will be continued after the transmission is resumed.
In the pass-through mode, input pin 9 PC7 low for a short time (0.5~3s), the module will exit the pass-through and switch to AT command mode.
In AT command mode, sending AT+TS=1 command will exit AT command mode and resume to pass-through mode.
The conversion logic of the pass-through mode and AT command mode is as follows:

Hi-Link HLK-B50 Dual Mode Bluetooth Module - Figure 4 Figure 4 Transmissive mode and AT command mode conversion logic diagram

4.3 Input and output pin function descriptions

Name	Chip pin	Description
Reset button input	RESET	Active high, external 10K pull-down resistor

required
Input high level module to restart the module
Function button input| PC7| Internal has been pulled up, pull down action;
pull low 0.5 to 3 seconds: exit the pass-through switch to AT command mode;
Pull down 8~20 seconds: restore factory default settings
Bluetooth connection status output| PD6| High level = not connected, low level = connected, the transmission channel is established;
When the pair binding function is enabled, the successful pair encryption means connected

Table 3 Input and output pin function descriptions

4.4 Bluetooth BLE device roles and connectivity

Devices at both ends of a Bluetooth BLE connection have fixed roles, always a host role and a slave role. The different roles define the corresponding operations and responsibilities of the devices.
The host takes the lead role in a Bluetooth connection by scanning the slave broadcast to discover the slave device and initiating and maintaining the connection to the selected slave device (identified by MAC address or Bluetooth name).
The slave broadcasts its own information, such as the device name, and the slave passively waits for a connection request from the host and accepts the request to make a successful Bluetooth connection. This module can be connected to multiple host devices at the same time when it is a slave.
The default mode of B50 module is slave mode, which can be switched by AT+ROLE command.
After two BLE devices establish a Bluetooth connection, they can send data to each other via Bluetooth (GATT).
The Bluetooth GATT service and feature UUID of this module can be modified by the AT command with the following default values:

Service UUID: 0000fff0-0000-1000-8000-00805f9b34fb

Feature UUID

| Operation permissions| Function definition
---|---|---
0000fff1-0000-1000-8000-00805f9b34fb| Read/Notify|

Module send, APP receive

0000fff2-0000-1000-8000-00805f9b34fb

| Write Without Response|

APP send, module receive

Table 4 Bluetooth pass-through service UUID default value

You can choose to open the pairing and binding function of Bluetooth connection, after opening, it can increase the security but the operation steps are increased accordingly, it is effective in slave or host mode, the pairing method is PASSKEY ENTRY, 6-digit Ping Code. after opening the binding function, the pairing and binding must be done to send and receive Bluetooth data, the unpaired device cannot transmit data through Bluetooth and the module.
In host mode, you need to set the MAC address of the target slave to be connected, the module will automatically scan and connect to the target slave device after starting, and will automatically reconnect if no slave is found or the connection is disconnected, etc. The interval of automatic reconnection can be set by AT+RECONNI command, the default is 5s, i.e. when it is not connected, it will try to reconnect once every 5 seconds until it is connected.

4.5 Bluetooth SPP connection

Devices that do not support Bluetooth BLE can establish a connection and transmit data through the traditional Bluetooth SPP protocol and module.

5 Quick start guide

5.1 Debug base board for testing

In order to enable users to quickly start verification and debugging of the module, we have developed a special B50 test base board, which is recommended for the first time when using the module.
The test base board is directly powered by USB and comes with USB to serial function. After connecting to the computer through USB cable, you can connect to the serial port of the module through USB to serial port, no need to connect additional serial cable, easy to use.

5.2 Quickly verify Bluetooth serial pass-through functionality

Our company has developed a special cell phone Bluetooth pass-through test APP for this module, so that users can use it. please refer to “HLK-B50 Bluetooth pass-through module cell phone APP instructions” for APP introduction and usage instructions.
Using the module test base and cell phone Bluetooth pass-through test APP, you can immediately start to test and verify the serial-Bluetooth pass-through function of the module.
The specific test operation procedure is as follows:

Connect the module to the test base correctly, and connect the test base to the computer via USB cable.
Open the corresponding serial port on the computer with the serial debugging tool.
Open the transmission test APP on the cell phone, the APP will automatically search the surrounding Bluetooth devices and display the list.
The default name of the B50 module is HLK_B50__**** and the suffix is The default name of the B50 module is HLK_B50B50, with the last four digits of the MAC address.

Figure 5 Diagram of the transmission test tool

After the APP is successfully connected to the module, the connection status LED on the test base will turn on, that is, it is connected.
At this time, you can send data to the serial port of the module in the serial debugging tool on the computer, and the sent content will be received and displayed by the cell phone APP as it is;
Send data to the module from the pass-through test APP on the cell phone, the sent content will be received by the module as it is and output to the serial port of the module, in The received data can be seen in the serial port debugging tool on the computer, and the effect is as follows:

Module serial port Mobile App side

Figure 6 Serial port and APP pass-through data testing

6 AT command

6.1 AT command format description

All AT command contents are in ASCII string format, and commands end with a carriage return newline character.
The settings are not lost after power down, and all settings are made to take effect after reboot.

Query class command:

Send	Answer
AT+=?\r\n	Query successfully:

AT+=\r\n
OK\r\n

Or query failure:

AT+=\r\n
ERROR\r\n

AT+=\r\n| Set up successfully:

AT+=\r\n
OK\r\n

Or set up failure:

AT+=\r\n
ERROR\r\n

\r\n stands for ASCII code: 0x0D 0x0A

6.2 List and description of AT commands

No

|

Command name

| Description| Parameter range|

Example

---|---|---|---|---

1

| VER|

Software version number

| Read only| Send| Answer
AT+VER=?| AT+VER=1.03(20092421)
OK

2

| MAC|

MAC address

| Read only| Send| Answer
AT+MAC=?| AT+MAC=112233445501
OK

3

| DEFAULT|

Restore the default configuration

| 1| Send| Answer
AT+DEFAULT=1| AT+DEFAULT=1
OK

4

| REBOOT|

Reboot module

| 1| Send| Answer
AT+REBOOT=1| AT+REBOOT=1
OK

5

| TS|

Restore passthrough mode

| 1| Send| Answer
AT+TS=1| AT+TS=1
OK

6

| NAME|

Module bluetooth name

7

| BAND|

Serial port baud rate

8

| CONNI|

Bluetooth connection interval

| 6~3200,unit 1.25ms, i.e. 7.5~4000ms,
Default value: 24
The smaller the transceiver, the faster the power consumption; the larger the transceiver, the slower the delay, the lower the power consumption| Send| Answer
AT+CONNI=?| AT+CONNI=24
OK
Send| Answer
AT+CONNI=8| AT+CONNI=8
OK

9

| ADVI|

Bluetooth broadcast interval

10

| ADVDATA|

Customized broadcast data

11

| ROLE|

BLE roles for modules

12

| ENCRYPT|

Pair binding enable

13

| PINCODE|

Matching code

14

| SCANMODE|

Connection scanning method in host mode

15

| PEERMAC|

MAC address of the slave that is automatically de- connected when the module is the host

16

| PEERNAME|

Bluetooth name of the slave that automatically goes to the connection when the module is the master

17

| AUTHPWG|

Access codes for OTA and over-the-air configurations

18

| RECONNI|

Bluetooth auto reconnect interval when module does host

| Integer, unit: s
0: represents only one connection attempt at startup, no reconnection
1~60: automatically reconnect after a specified number of seconds after the connection is disconnected
Default value: 5| Send| Answer
AT+RECONNI=?| AT+RECONNI=0
OK
Send| Answer
AT+RECONNI=10| AT+RECONNI=10
OK

19

| UUIDS|

Bluetooth transmissions service UUID

| 32 hexadecimal numbers
Default value: 0000fff000001000800000805f9b34fb| Send
AT+UUIDS=0000fff000001000800000805f9b34fb
Answer
AT+UUIDS=0000fff000001000800000805f9b34fb
OK

20

| UUIDR|

Read feature UUID in passthrough service (sent by module, received by APP)

| 32 hexadecimal numbers
Default value: 0000fff100001000800000805f9b34fb|

21

| UUIDW|

Write feature UUID in passthrough service (sent by APP, received by module)

| 32 hexadecimal numbers
Default value: 0000fff200001000800000805f9b34fb|

22

| DISCONN|

Proactively disconnect all current bluetooth connections to the module

| 1| Send| Answer
AT+DISCONN=1| AT+DISCONN=1
OK

23

| ADVEN|

Module bluetooth broadcast enable

| 0 Disable Bluetooth broadcasting for the module
1 Enables Bluetooth broadcasting for the module
Default value: 1
When disabled, the module cannot be scanned by cell phones or other Bluetooth hosts| Send| Answer
AT+ADVEN=?| AT+ADVEN=0
OK
Send| Answer
AT+ADVEN=1| AT+ADVEN=1
OK

24

| BTNAME|

Module BT legacy bluetooth name

25

| BTMODE|

SPP and GATT mode settings, dual-mode or single-mode

26

| BTMAC|

BT legacy blue MAC address (not the same as BLE MAC)

| Read only| Send| Answer
AT+BTMAC=?| AT+BTMAC=112233445501
OK

Table 5 AT command list and description

7 Wireless setup and query via bluetooth

You can check and set the parameters of the module through Bluetooth wireless in the cell phone APP, please refer to “HLK-B50 Bluetooth Transparent Module Please refer to the “HLK-B50 Bluetooth Transparent Module Mobile Phone APP Instructions” for detailed operation.

8 OTA Function

The firmware of the module can be upgraded wirelessly via Bluetooth in the cell phone APP, please refer to “HLK-B50 Bluetooth Transparent Module Mobile Phone APP Instructions for use”.

FCC Caution:
Any Changes or modifications not expressly approved by the party responsible for compliance could void the user’s authority to operate the equipment.

This device complies with part 15 of the FCC Rules. Operation is subject to the following two conditions: (1) This device may not cause harmful interference, and (2) this device must accept any interference received, including interference that may cause undesired operation.

IMPORTANT NOTE:

NOTE: This equipment has been tested and found to comply with the limits for a Class B digital device, pursuant to part 15 of the FCC Rules. These limits are designed to provide reasonable protection against harmful interference in a residential installation. This equipment generates, uses and can radiate radio frequency energy and, if not installed and used in accordance with the instructions, may cause harmful interference to radio communications. However, there is no guarantee that interference will not occur in a particular installation. If this equipment does cause harmful interference to radio or television reception, which can be determined by turning the equipment off and on, the user is encouraged to try to correct the interference by one or more of the following measures:
—Reorient or relocate the receiving antenna.
—Increase the separation between the equipment and receiver.
—Connect the equipment into an outlet on a circuit different from that to which the receiver is connected.
—Consult the dealer or an experienced radio/TV technician for help.

FCC Radiation Exposure Statement:
This equipment complies with FCC radiation exposure limits set forth for an uncontrolled environment .This equipment should be installed and operated with minimum distance 20cm between the radiator& your body.
The modular transmitter must comply with any applicable RF exposure requirements (as defined §2.1091 and §2.1093,) in its final configuration, per KDB996369 D03.

OEM/Integrators Installation Manual

List of applicable FCC rules This module has been tested and found to comply with part 15.247 requirements for Modular Approval.
Summarize the specific operational use conditions This module can support both Bluetooth SPP and GATT pass-through, and various devices with serial ports can use Bluetooth wirelessly to send and receive data simply and quickly through this module. The input voltage to the module should be nominally 3.3 VDC, typical value 3.3VDC and the ambient temperature of the module should not exceed 85°C.
Limited module procedures N/A
Trace antenna designs N/A
Antennas The module of FR5082DM has a PCB antenna, and the maximum gain is 2.5dBi.

Label and compliance information When the module is installed in the host device, the FCC ID label must be visible through a window on the final device or it must be visible when an access panel, door or cover is easily re-moved. If not, a second label must be placed on the outside of the final device that contains the following text: Contains Transmitter Module
FCC ID: 2AD56HLK-B50, the FCC ID can be used only when all FCC ID compliance requirements are met.

Information on test modes and additional testing requirements

a) The modular transmitter has been fully tested by the module grantee on the required number of channels, modulation types, and modes, it should not be necessary for the host installer to re-test all the available transmitter modes or settings. It is recommended that the host product manufacturer, installing the modular transmitter, perform some investigative measurements to confirm that the resulting composite system does not exceed the spurious emissions limits or band edge limits (e.g., where a different antenna may be causing additional emissions).
b) The testing should check for emissions that may occur due to the intermixing of emissions with the other transmitters, digital circuitry, or due to physical properties of the host product (enclosure). This investigation is especially important when integrating multiple modular transmitters where the certification is based on testing each of them in a stand-alone configuration. It is important to note that host product manufacturers should not assume that because the modular transmitter is certified that they do not have any responsibility for final product compliance.
c) If the investigation indicates a compliance concern the host product manufacturer is obligated to mitigate the issue. Host products using a modular transmitter are subject to all the applicable individual technical rules as well as to the general conditions of operation in Sections 15.5, 15.15, and 15.29 to not cause interference. The operator of the host product will be obligated to stop operating the device until the interference has been corrected.

Additional testing, Part 15 Subpart B disclaimer
The final host / module combination need to be evaluated against the FCC Part 15B criteria for unintentional radiators in order to be properly authorized for operation as a Part15 digital device. The host integrator installing this module into their product must ensure that the final composite product complies with the FCC requirements by a technical assessment or evaluation to the FCC rules, including the transmitter operation and should refer to guidance in KDB 996369. For host products with certified modular transmitter, the frequency range of investigation of the composite system is specified by rule in Sections 15.33(a)(1) through (a)(3), or the range applicable to the digital device, as shown in Section 15.33(b)(1), whichever is the higher frequency range of investigation. When testing the host product, all the transmitters must be operating. The transmitters can be enabled by using publicly available drivers and turned on, so the transmitters are active. In certain conditions it might be appropriate to use a technology- specific call box (test set) where accessory devices or drivers are not available. When testing for emissions from the unintentional radiator, the transmitter shall be placed in the receive mode or idle mode, if possible. If receive mode only is not possible then, the radio shall be passive (preferred) and/or active scanning. In these cases, this would need to enable activity on the communication BUS (i.e., PCIe, SDIO, USB) to ensure the unintentional radiator circuitry is enabled. Testing laboratories may need to add attenuation or filters depending on the signal strength of any active beacons (if applicable) from the enabled radio(s). See ANSI C63.4, ANSI C63.10 and ANSI C63.26 for further general testing details.