RF-Star RF-BM-ND04 User manual

nRF52832 Bluetooth Low Energy 5.0
Master-Slave Module and Protocol
Version: V1.4
Shenzhen RF-star Technology Co., Ltd.
Jan. 8th, 2021

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RF-BM-ND04
RF-BM-ND04I
RF-BM-ND08

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Table of Contents
Table of Contents................................................................................................................................................................ 2
Table of Tables..................................................................................................................................................................... 5
Table of Figures................................................................................................................................................................... 5
1 Summary............................................................................................................................................................................ 6
2 Overview ............................................................................................................................................................................ 7
2.1 Introduction........................................................................................................................................................... 7
2.2 Features ................................................................................................................................................................ 7
2.3 Supporting Working Mode.............................................................................................................................. 8
2.4 Default Configuration at Slave Mode ......................................................................................................... 8
2.5 Default Configuration at Beacon Mode ..................................................................................................... 9
2.6 Device Status ...................................................................................................................................................... 9
2.7 Multi-Connection ................................................................................................................................................ 9
3 Package and Pin Assignment ..................................................................................................................................11
3.1 RF-BM-ND04(I) ................................................................................................................................................11
3.2 RF-BM-ND08(I) ................................................................................................................................................14
4 UART Transparent Transmission Protocol (Bridge Mode) ...........................................................................17
5 BLE Protocol Specification (APP Interface) .......................................................................................................18
UART Service UUID...............................................................................................................................................18
BLE Data Receiving UUID (RX Characteristic) ...........................................................................................18
BLE Data Transmitting UUID (TX Characteristic).......................................................................................18
AT Command Operation UUID...........................................................................................................................18
Device Information UUID: 0x180A....................................................................................................................19
Manufacturer Name................................................................................................................................................19
Hardware Revision .................................................................................................................................................19
Firmware Revision ..................................................................................................................................................19
System ID...................................................................................................................................................................19
Generic Access UUID: 0x1800 ..........................................................................................................................20
Device Name.............................................................................................................................................................20
Device Appearance ................................................................................................................................................20
Peripheral Preferred Connection Parameters..............................................................................................20
Central Address Resolution.................................................................................................................................20

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6 AT Command..................................................................................................................................................................21
6.1 AT Command Format .....................................................................................................................................21
6.2 AT Command List.............................................................................................................................................22
6.3 Detailed AT Command...................................................................................................................................24
•Enter AT Command Mode ......................................................................................................................24
•Exit AT Command Mode .........................................................................................................................24
•Device Name...............................................................................................................................................24
•MAC Address ..............................................................................................................................................25
•Serial Port Echo .........................................................................................................................................25
•Device Status Display..............................................................................................................................27
•Device Role..................................................................................................................................................28
•Slave Role Broadcast Parameters......................................................................................................29
•Connection Interval...................................................................................................................................30
•Slave Service ..............................................................................................................................................31
•Master Scan.................................................................................................................................................32
•Master Connection ....................................................................................................................................34
•Disconnect....................................................................................................................................................35
•Automatically Reconnection ..................................................................................................................36
•Designate Role Who Sends Data (Master-Slave at the Same Time)....................................38
•Display Current Connected Devices ..................................................................................................38
•Designate Transmission Device...........................................................................................................39
•Delete Device..............................................................................................................................................40
•Observer........................................................................................................................................................41
•Beacon...........................................................................................................................................................42
•Tx Power.......................................................................................................................................................43
•Sleep Mode..................................................................................................................................................44
•Baud Rate.....................................................................................................................................................46
•User Authentication...................................................................................................................................47
•Restart Device ............................................................................................................................................48
•Reset Device ...............................................................................................................................................48
•Firmware Version.......................................................................................................................................48
Query the firmware version information and the date........................................................................................48
7 Transparent Transmission Test ...............................................................................................................................49

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7.1 Test by APP (Android)....................................................................................................................................49
7.2 Test by PC End.................................................................................................................................................52
Preparation before Use................................................................................................................................52
Connection Steps...........................................................................................................................................52
8 iOS APP Programming Reference.........................................................................................................................58
9. MCU Reference Code (Transparent Transmission) ......................................................................................61
10 Application, Implementation and Layout ...........................................................................................................62
10.1 Module Parameters ......................................................................................................................................62
10.2 Reference Design .........................................................................................................................................62
10.3 Antenna .............................................................................................................................................................63
10.3.1 Antenna Design Recommendation............................................................................................63
10.3.2 IPEX Connector ................................................................................................................................64
10.3.3 Antenna Output Mode Modification ...........................................................................................65
10.4 Basic Operation of Hardware Design....................................................................................................65
10.5 Trouble Shooting ...........................................................................................................................................66
10.5.1 Unsatisfactory Transmission Distance .....................................................................................66
10.5.2 Vulnerable Module ...........................................................................................................................67
10.5.3 High Bit Error Rate...........................................................................................................................67
10.6 Electrostatics Discharge Warnings.........................................................................................................67
10.7 Soldering and Reflow Condition ..............................................................................................................67
10.8 Optional Packaging ......................................................................................................................................69
11 Revision History ..........................................................................................................................................................70
12 Contact Us ....................................................................................................................................................................72
Appendix A: Certifications .............................................................................................................................................73
1 SRRC .......................................................................................................................................................................73
2 FCC...........................................................................................................................................................................73
3 CE..............................................................................................................................................................................74
Appendix B: Power Consumption Test Screenshot ............................................................................................75
1 Sleep Mode: 2.76 μA..........................................................................................................................................75
2 Broadcast Mode...................................................................................................................................................75
2.1 200 ms Broadcast Cycle: 76.98 μA .................................................................................................75
2.2 500 ms Broadcast Cycle: 32.79 μA .................................................................................................76
2.3 1000 ms Broadcast Cycle: 17.53 μA...............................................................................................76

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3 Connection Mode ................................................................................................................................................77
3.1 45 ms Connection Interval: 80.35 μA..............................................................................................77
3.2 100 ms Connection Interval: 27.25 μA...........................................................................................77
Table of Tables
Table 1. Power Consumption of nRF52832 .................................................................................................... 8
Table 2. Pin Functions of RF-BM-ND04(I).....................................................................................................12
Table 3. Pin Functions of RF-BM-ND08(I).....................................................................................................15
Table 4. AT Command Format Table................................................................................................................21
Table 5. AT Command List...................................................................................................................................22
Table 6. Temperature Table of Soldering and Reflow................................................................................67
Table of Figures
Figure 1. Multi-Connection Diagram ................................................................................................................10
Figure 2. PCB Footprint of RF-BM-ND04 ......................................................................................................11
Figure 3. PCB Footprint of RF-BM-ND04I.....................................................................................................11
Figure 4. Pin Assignment of RF-BM-ND04(I) ...............................................................................................12
Figure 5. PCB Footprint of RF-BM-ND08 ......................................................................................................14
Figure 6. PCB Footprint of RF-BM-ND08I.....................................................................................................14
Figure 7. Pin Assignment of RF-BM-ND08(I) ...............................................................................................15
Figure 8. Reference Design ................................................................................................................................63
Figure 9. Recommendation of Antenna Layout ...........................................................................................64
Figure 10. Specification of Antenna Seat.......................................................................................................64
Figure 11. Specification of IPEX Wire .............................................................................................................64
Figure 12. Antenna Output Mode Change of RF-BM-ND04I..................................................................65
Figure 13. Antenna Output Mode Change of RF-ND08(I).......................................................................65
Figure 14. Recommended Reflow for Lead-Free Solder.........................................................................68
Figure 15. Optional Packaging Mode ..............................................................................................................69

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1 Summary
RF-BM-ND04(I) and RF-BM-ND08 are RF modules based on Nordic BLE SoC nRF52832 with ARM® Cortex®-M4 32-bit
processor. It integrates a 32.768 kHz and a 32 MHz crystal, an LC filter, an antenna matching and a meander line
inverted-F PCB antenna / or an IPEX connector. The modules support BLE stack v5.0 including the high-speed 2 Mbps
feature and can be preprogrammed with serial interface communication protocols, such as NFC, ANT and 2.4 GHz
proprietary for simple programming. The modules also support Bluetooth mesh which can be run concurrently with
Bluetooth LE, enabling smartphones to provision, commission, configure and control mesh nodes. The module has NFC-
A Tag for use in simplified pairing and payment solutions. It also has numerous digital peripherals and interfaces such
as ADC, PDM, PWM, I2C and I2S for many applications. It features low power consumption, small size, robust connection
distance, and rigid reliability. 1.27-mm pitch stamp stick package for easy assembling and cost-effective PCB design.
RF-star can provide customers with the integration of the entire profiles, applications, radio and BLE protocol stack. With
compliance to Bluetooth Low Energy standard, the RF-star’s modules enable the creation of a new market for tiny, cost-
effective and power-efficient wireless consumer products such as watches, medical sensors, mice, TV remote controls
and fitness trainers.

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2 Overview
2.1 Introduction
The Bluetooth LE modules which are mentioned in this document can work in bridge mode (transparent transmission
mode).
After the module starts to broadcast, a smartphone with a specific APP running will scan and pair with it. When the
connection is successful, the smartphone can monitor and control the module through Bluetooth protocol.
In bridge mode, the user CPU can communicate with the mobile device bi-directionally through the serial ports of
modules. Users can also manage and control certain communication parameters through specific AT commands of serial
ports. The detailed meaning of the user data is defined by the upper applications. Mobile devices can write the module
through the APP. And the data are written will be sent to the user CPU through serial ports. Then the module will transmit
the data packet from the user CPU to the mobile devices automatically. Under the development in this mode, the user
needs to undertake the code design for the master CPU and the APP for mobile devices.
In order to ensure the stability of the firmware, the module will start to work normally after 500 ms of poweron.
When transmitting a big size data packet, it is recommended to start working after the module is connected for
6 s. MTU, connection interval, and other operations need to be confirmed when a connection is established. If
the high-speed transparent transmission is carried out at this time, packet loss or device jamming is very easy
to occur.
2.2 Features
1. Easy to use, no need of any application experience of Bluetooth protocol stack.
2. Support BLE master mode, slave mode, master-slave mode and Beacon mode.
3. Support concurrent slave mode and master, that is, the module can connect to other slave devices when it is
connected by one master device.
4. Support multi-connection during master mode and master-slave mode. Under master-slave mode, 7 slave devices
can be connected at the same time, and it also can be connected as a slave device by another master device at
the same time.
5. Default connection interval of 20 ms, which makes a quick connection and enhances the compatible stability of
Android and iOS phones.
6. UART design for user interface, full-duplex bi-directional communication, and support the minimum baud rate of
4800 bps and the maximum baud rate of 460800 bps.
7. Support software reset module by AT command.

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8. Support acquire and modify the MAC address (to take effect after resetting) by AT command.
9. Support adjust the Bluetooth connection interval and control different transmit rates (dynamic power consumption
adjustment) by AT command.
10. Support adjust the transmit power, modify the broadcast interval, modify the serial port baud rate, modify the module
name, by AT commands, please check for details in AT Command.
11. Support modify Service UUID by AT command.
12. AT commands can be sent through APP.
13. High-speed transparent transmission rate and the maximum is 46 kB/s (Use standard hardware flow control).
14. Ultra-low working power consumption, the measured power consumption of the module is as follows:
Table 1. Power Consumption of nRF52832
Event
Average Current
Test Condition / Remark
Sleep
2.76 µA
Broadcast
76.98 µA
Broadcast interval: 200 ms
Broadcast
32.79 µA
Broadcast interval: 500 ms
Broadcast
17.53 µA
Broadcast interval: 1000 ms
Broadcast
8.90 µA
Broadcast interval: 2000 ms
Broadcast
4.27 µA
Broadcast interval: 5000 ms
Connection
80.35 µA
Connection interval: 45 ms
Connection
27.25 µA
Connection interval: 150 ms
2.3 Supporting Working Mode
The device supports four working modes as below:
1. BLE slave mode
2. BLE master mode
3. BLE master-slave mode
4. Beacon mode
The default role after power-on is the slave mode. The role can be switched to adjust the working mode through the AT
command "AT+ROLE". Please check the AT Command in detail. In the Beacon mode, the serial port is closed, the
mode only can be switched through the mobile APP.
2.4 Default Configuration at Slave Mode
1. Device name: RF-STAR-SMMT.
2. Broadcast interval: 200 ms.

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3. Connection interval: 20 ms.
4. 128-bit UUID (by default)
5. Broadcast mode: connectable
6. Device status: transparent transmission
2.5 Default Configuration at Beacon Mode
1. Company ID: 0x0059 (Nordic).
2. Major UUID: 0x0102.
3. Minor UUID: 0x0304.
4. RSSI: -50 dBm.
5. UUID: 0x01, 0x02, 0x03, 0x04, 0x05, 0x06, 0x07, 0x08, 0x09, 0x0A, 0x0B, 0x0C, 0x0D, 0x0E, 0x0F, 0x10.
The serial port is closed and unavailable in this mode.
2.6 Device Status
1. DEVICE START: The device starts to work.
2. S:CONNECTED: BLE slave is successfully connected.
3. S:DISCONNECTED: BLE slave is disconnected.
4. B:CONNECTED: Beacon is successfully connected.
5. B:DISCONNECTED: Beacon is disconnected.
6. “XX:XX:XX:XX:XX:XX CONNEDTED”: BLE master is successfully connected (The string in red is the MAC address
of the connected slave).
7. “XX:XX:XX:XX:XX:XX DISCONNECTED”: BLE master is disconnected (The string in red is the MAC address of the
disconnected slave).
8. CONNECT XX:XX:XX:XX:XX:XX TIMEOUT: The time when the BLE master connects to the slave device is overtime
(The string in red is the MAC address of the connected slave device). When devices are not found within 5 s after
the command is operated, a timeout will be prompted.
9. BUSY...: The device is busy, please wait for the device to finish processing the current task.
10. WAKE UP: Serial port wake up
11. DEVICE ERROR!: An abnormal error occurred in the device. The device will automatically restore factory settings.
The above states can be turned on or off by the AT command. For details, please refer to AT Command.
2.7 Multi-Connection
1. Support multi-connection during master mode and master-slave mode. Under master-slave mode, 7 slave devices
can be connected at the same time, and it also can be connected as a slave device by another master device at

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the same time.
2. If AT+CONNECT command failed to connect to the device (prompt FAIL), please refer to the command description
for the reason.
3. Multi-connection means multiple devices automatically reconnect. When an opposite device disconnects
abnormally, the device will initiate reconnection. Please refer to the command description.
4. During multi-connection, the designated data transmission handle function is not saved after power off, and the
device will transmit data with the device with a handle value of 0 by default. If the device with the corresponding
handle is disconnected, the handle value will be automatically switched to the next effective handle. (The handle
can be queried with the command AT+CNT_LIST).
5. The user disconnects the device which is sets as automatic reconnection by AT commands, and the current
automatic reconnection of the device will be failed. It will take effect after the next abnormal disconnection.
Recommendation:
The source of multi-connection data transmission is more complicated, such as the master-slave: the data may come
from the following 4 devices, so the data source should be included in the data packet, otherwise, it cannot be identified
which device the data came from.
Figure 1. Multi-Connection Diagram

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3 Package and Pin Assignment
3.1 RF-BM-ND04(I)
RF-BM-ND04 is pin to pin compatible with and RF-BM-ND04I. The difference is that the antenna of RF-BM-ND04 is
PCB type, while RF-BM-ND04I is IPEX type.
Figure 2. PCB Footprint of RF-BM-ND04
Figure 3. PCB Footprint of RF-BM-ND04I

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Figure 4. Pin Assignment of RF-BM-ND04(I)
Table 2. Pin Functions of RF-BM-ND04(I)
Pin
Name
Function
Description
1
GND
GND
Ground
2
VCC
VCC
Power supply: 1.7 V ~ 3.6 V. Recommended to 3.3 V.
3
P21 / RST
I/O
Reset, active low.
4
P22
I/O
5
P23
I/O
6
P24
I/O
7
P25
I/O
8
P28
I/O
9
P29
I/O
10
P30
I/O
11
P26
I/O
12
P27
I/O
13
P02
I/O
14
P03
I/O
15
P04
I/O

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16
P05
RTS
Module output signal (Standard hardware flow control: Require
To Send). When it is at a high level, the module serial port is
busy, and the MCU is not allowed to send data to the module
serial port. When it is at a low level, the MCU is allowed to send
data to the module serial port.
17
P06
TX
Serial port TX
18
P07
CTS
Module input signal (Standard hardware flow control: Clear To
Send). When it is at a high level, the MCU serial port is busy,
and the module will not send data to the MCU serial port. When
it is at a low level, the module will send data to the MCU serial
port.
19
P08
RX
Serial port RX
20
P09
I/O
21
P10
I/O
22
P11
I/O
23
P12
I/O
24
P13
Wakeup IO
When the module is in a sleep state, the module can be
awakened through this IO.
Active on the falling edge
25
P14
I/O
26
P15
I/O
27
P16
I/O
28
SWDIO
－
Serial Wire Debug I/O for debugging and programming
29
SWCLK
－
Serial wire debug clock input for debugging and programming
30
P17
Status
indicator
Slave role (including Beacon) connection status indicator: in
low level during connection (LED always on).
31
P18
Status
indicator
Master role connection status indicator: in low level during
connection (LED always on).
32
P19
RESTORE
All parameters will be reset to factory settings after this pin is
set low for 3 s.
33
P20
I/O

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3.2 RF-BM-ND08(I)
RF-BM-ND08 is pin to pin compatible with and RF-BM-ND08I. The difference is that the antenna of RF-BM-ND08 is
PCB type, while RF-BM-ND08I is IPEX type. SWD debugging ports are on the bottom side of the module, which is not
pulled out in the stamp half hole way, please refer to the module pin diagram for details.
Figure 5. PCB Footprint of RF-BM-ND08
Figure 6. PCB Footprint of RF-BM-ND08I

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Figure 7. Pin Assignment of RF-BM-ND08(I)
Table 3. Pin Functions of RF-BM-ND08(I)
Pin
Name
Function
Description
1
ANT
—
2
GND
GND
Ground
3
VCC
VCC
Power supply: 1.7 V ~ 3.6 V. Recommended to 3.3 V.
4
P25
I/O
5
P17
Status
indicator
Slave role (including Beacon) connection status indicator: in
low level during connection (LED always on).
6
P21/RST
I/O
Reset, active low.
7
P13
Wakeup IO
When the module is in a sleep state, the module can be
awakened through this IO.
Active on the falling edge
8
P28
I/O
9
P27
I/O
10
P26
I/O
11
P09
I/O
12
P10
I/O
13
P19
RESTORE
All parameters will be reset to factory settings after this pin is
set low for 3 s.
14
P20
I/O
15
P05
RTS
Module output signal (Standard hardware flow control: Require
To Send). When it is at a high level, the module serial port is

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busy, and the MCU is not allowed to send data to the module
serial port. When it is at a low level, the MCU is allowed to
send data to the module serial port.
16
P07
CTS
Module input signal (Standard hardware flow control: Clear To
Send). When it is at a high level, the MCU serial port is busy,
and the module will not send data to the MCU serial port. When
it is at a low level, the module will send data to the MCU serial
port.
17
P06
TX
Serial port TX
18
P08
RX
Serial port RX
19
P03
I/O

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4 UART Transparent Transmission Protocol (Bridge Mode)
The bridge mode means to set up a bi-directional communication way between user CPU and mobile devices by the
mutual connection between serial port and user CPU. Users can reset serial port baud rate and BLE connection interval
by the specified AT commands (see the section “AT Command”). The module will have different data handling capabilities,
as per different serial port baud rates and BLE connection intervals.
The hardware protocol of serial port: 115200 bps, 8, no parity, 1 stop bit.
Except for Beacon mode, the serial port is open by default in any mode. If this function needs to be closed, please use
the "AT+SLEEP=1" command to close the serial port.
When the module serial port receives data and transmits it to the mobile device, there is no strict requirement for the
serial port data packet. When the RTS of the module is set high, it indicates that the receive buffer of the serial port is
full (maximum buffer is 3904 bytes), or the serial port is busy.
Data packets from mobile devices to the module must be sub-packed automatically (into 1 ~ 244 bytes per packet)
before sending. The module will transmit the packets to the master RXD in turn, after received the packets.
Most serial port tools on PC do not have CTS detection. For reliable transparent transmission, please use flow
control.It is recommended to use the software SecureCRT.

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5 BLE Protocol Specification (APP Interface)
UART Service UUID
6E400001B5A3F393E0A9E50E24DCCA9E
BLE Data Receiving UUID (RX Characteristic)
Characteristics UUID
6E400002B5A3F393E0A9E50E24DCCA9E
Executable operations
WRITE, WRITE NO RESPONSE
Remarks
The BLE input is transmitted to the serial port output: After APP writes to this channel
through the BLE API interface, the data will be output from the serial port TX.
BLE Data Transmitting UUID (TX Characteristic)
Characteristics UUID
6E400003B5A3F393E0A9E50E24DCCA9E
Executable operations
Notify
Remarks
The serial port input is transmitted to the BLE output, and the data input from the serial
port RX will be notified in this channel and sent to the mobile device.
AT Command Operation UUID
Characteristics UUID
6E400004B5A3F393E0A9E50E24DCCA9E
Executable operations
NOTIFY, WRITE, WRITE NO RESPONSE
Remarks
Supports all commands in the command list, any data will be processed as commands
(do not use +++ to enter the command mode), and users can operate without sending
carriage returns and line feeds (CRLF). The serial port must end with a CRLF.
The master needs to open notify to receive the data sent by the module.

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Device Information UUID: 0x180A
Manufacturer Name
Characteristics UUID
0x2A29
Executable operations
READ
Remarks
RF-STAR-SMMT (Shenzhen RF-star Technology Co., Ltd. Transparent transmission
module working as master and slave at the same time)
Hardware Revision
Characteristics UUID
0x2A27
Executable operations
READ
Remarks
Module hardware version reading channel. The module hardware version can be
obtained by reading the channel. Such as RF-BM-ND04 / RF-BM-ND08, which
indicates that this firmware is suitable for the corresponding model of the module.
Firmware Revision
Characteristics UUID
0x2A26
Executable operations
READ
Remarks
Module firmware version reading channel. The module firmware version can be
obtained by reading the channel. The format is v0.2.5, Dec 28 2020,17:58:32, it
Indicates the firmware version V0.2.5 generated at 17:58:32 on December 28th, 2020.
System ID
Characteristics UUID
0x2A23
Executable operations
READ
Remarks
Module information acquisition channel. The module ID can be obtained by reading
this channel. The format is as xxxxxx0000xxxxxx, and xx is the physical address of the
module chip MAC, six bytes, low byte first.