AT Command

warning_yellow.png NOTE:To get a ‘better’ Bluetooth experience on BLE 4.1 modules, we highly recommand you to update the newest firmware first.

AT is the abbreviation of attention. AT command is the communication command used to configure Bluetooth parameters. It begins with AT, end with <CR+LF> (carriage return and line feed).

warning_yellow.png NOTE: <CR+LF> is not a part of AT Command.

AT Command List

AT Command Function Parameters Description
AT+ROLE= X Set Bluetooth mode “?” Query Bluetooth working mode
“ROLE_CENTRAL” Set as the central device
“ROLE_PERIPHERAL” Set as the peripheral device
Return Current Mode
Return “OK”
Return “OK”
AT+NETWORK= Set network mode “?” Query the network mode
“P2P” Set to peer connection
“STAR” Set to star network
Return Current Network Mode
Return “OK”
Return “OK”
AT+MIN_INTERVAL= Set the minimum communication interval “?” Query the current minimum communication interval (10~99999ms) Return Minimum Communication Interval
Return “OK”
AT+MAX_INTERVAL= Set the maximum communication interval “?” Query the current maximum communication interval (10~99999ms) Return Maximum Communication Interval
Return “OK”
AT+BIND= Set binding Bluetooth address “?” Query the current binding MAC address
e.g.: 0x0017ea9397e1 Set Bluetooth MAC address in need
Return 0x000000000000(Default)
Return “OK”
AT+CMODE= Set BLE connection mode “?” Query the current connection mode
“UNIQUE” Specify the connection mode
“ANYONE” Set to free connection
Return BLE connection mode
Return “OK”
AT+MAC= Query the Bluetooth address “?” Query the current Bluetooth MAC address Return the current Bluetooth MAC address
AT+NAME= Set the name “?” Query the Bluetooth device name “DFBLEduino2” Return Bluetooth device name Return “OK”
AT+SETTING= Modify/Reset to default mode “?” Query the current setting
“DEFAULT” Reset to initial setting
“DEFPERIPHERAL” Reset to initial slave setting
“DEFCENTRAL” Reset to initial host setting
Return the device Current Status
Return “OK”
Return “OK”
Return “OK”
AT+USB_MONITOR= Turn the USB monitor ON/OFF “?” Query the current USB monitor
“ON” Turn on the USB monitor
“OFF” Turn off the USB monitor
Return the current USB monitor status
Return “OK”
Return “OK”
AT+HELP= Get help from AT command “ALL” Query all AT commands help information Return AT Command help information
AT+NET_INF= Query device information in the current network “?” Query device network information Return the current network information
AT+VERSION= Query the firmware version “?” Query firmware version information Return firmware version information
AT+RSSI= Query the RSSI value “?” Query the RSSI value Return the current RSSI value (Return -000 when where is no connection)
AT+P= Query & Set P(n, n=0,1,2,3...) status “?” Set IO pins to input mode and query the voltage “1” Set IO pins to output mode and output HIGH voltage
“0” Set IO pins to output mode and output LOW voltage
Eg:AT P47=? (Return 0 or 1)
Eg:AT P47=1(Return “OK”)
Eg:AT P47=0 (Return “OK”)
AT+WL= Query/Declare the White List “?” Query the White List “NONE” Declare the White List Return White List MAC address list Return “OK”
AT+LOWPOWER= Query & Set the low-power mode “?” Query the low-power mode
“ON” Turn on the low-power mode
“OFF” Turn off the low-power mode
Return current status
Return “OK”
Return “OK”
AT+EXIT Exit the AT command mode Exit the AT command mode Return “OK”

Configure the BLE through AT command

1. Open the Arduino IDE.

2. Select the correct serial port in Menu->Tool->Serial port

3. Open the Serial monitor (on the upper right of the IDE windows)

4. Select the "No line ending"(①) and 115200 baud(②) in the pull-down menu

5. Type "+++"(③) like this and press send button(④)

6. If the AT Command Mode is successfully access , you will receive "Enter AT Mode"(⑤) from it.

Fig1: +++ enter the AT CMD Mode

7. Select the "Both NL & CR"(①) and 115200 baud(②) in the pull-down menu

8. Type or copy the AT command in the dialog(③) like this and press send button(④)

9. If the BLE is successfully configured , you will receive "OK"(⑤) from it.

Fig1: enter the AT command,remember selecting the Both NL & CR

10. If received "ERROR CMD" instead, try sending it again or you should check whether the command is correct or not.

11. USE “AT+EXIT” to exit AT Mode

12. You can input AT+HELP=ALL to query all AT Command information

Fig1: Enter AT+HELP=? to get AT Command List

Bluetooth Connection

Before using BLE4.1 series devices, it is better to know some key buttons first.

Below is the BLE4.1 minimum system circuit diagram for your reference: Fig1: the BLE4.1 minimum system circuit diagram Fig1: BLE4.1 Minimum System Schematic

Smartphone Bluetooth Connection

Different from the traditional Bluetooth (such as Bluetooth headset), BLE4.1 need specified eigenvalue and device service ID to connect smartphone. The direct connection between BLE and smartphone device manager will lead to communication problems. Therefore, it needs a the third party APP, such as BunoBasicDemo (published by DFRobot), BLE Device Monitor from TI .etc. In this section, we'll take BunoBasicDemo published by DFRobot as an example.

Fig1: Scanning

Fig2: Connected

Fig3: Send Data

Fig4: Print what it received

PC Bluetooth Connection

The direct connection between PC and BLE4.1 built-in Bluetooth is not available for temporarily (similar to smartphone, PC also need another software to realize the connection. The development is still in planning)

Bluetooth P2P Communication

The procedure of BLE4.1 P2P connection is similar to BLE4.0, and the only difference is the P2P mode command.

There are two devices in all, one should be set as the master device(ROLE_CENTRAL) and the other one should be set as the slave device(ROLE_PERIPHERAL). Config two BLE4.1 devices as P2P connection mode with AT+NETWORK=P2P (Default: P2P mode).

Fig1: set the connection mode

Fig2: set the device as central mode

Restart BLE4.1 device and begin the approach connection.


  1. The first time you press and hold the host BOOT button is only for add the new devices to the white list. It doesn't need the same operation for the second connection.
  2. BLE 4.1 device is also compatible with BLE4.0 devices (Bluno 1st generation). And BLE 4.0 only supports P2P connection, so it doesn't need to set the connection mode for 4.0, just BLE 4.1 only.

Bluetooth Star Network Connection

The star network connection mode is similar to the P2P connection mode, the difference between them in setting is that the star network uses the command AT+NETWORK=STAR. The light LINK suggests the node device has been added to the white list of the central device and then it will connect the listed device automatically.

Fig1: Set Star Network Connection

warning_yellow.png NOTE:Star network connection is only for BLE4.1 device, not applicable to Bluno 1st generation (BLE4.0) and other BLE brands device.

In the star connection, Bluetooth device adopt special data packet compression method. You can use Arduino library to realize network data transmit. Click the link to download Arduino library files and Arduinojson library files. During the connection, the slave device which first connected to the host will get ID: 1 and hereby superimposed. The sample code shows how to get network ID of the device and ID of the data source. You’d better to power the device in turn when build star network.

#include <DFRobot_Bluno2.h>
#include <ArduinoJson.h>

DFRobot_Bluno2 blunoNet;
int blunoID=0;
void setup()

void loop()
  uint8_t event=blunoNet.getEvent();//queue
      eventNode e = blunoNet.popEvent();

      StaticJsonBuffer<200> jsonBuffer;
      JsonObject& root = jsonBuffer.parseObject((const char *)e.payload);
      if (!root.success()) {
      int s =  root["r"].size();
      for(int i = 0; i < s; i++){
          blunoID = root["r"][i]["i"].as<int>();
    case EVENT_DATA:
      eventNode e = blunoNet.popEvent();
      blunoNet.sendPacket(e.src, blunoID, "hello12345678901234567890",26);
    default: //no event
    blunoNet.sendPacket(!blunoID, blunoID, &message,1);

Bluetooth Low Power Consumption Mode

After Bluetooth enter low power consumption mode, the BLE 4.1 consumes lower than 10uA, and it can still broadcast and keep data interaction. With command AT+LOWPOWER=ON, BLE4.1 device will enable low power consumption mode after you reboot the device. BLE4.1 device will enter this mode in 10s. You can also use AT+BOOT to make a software reboot. Here is something you should notice: The MCU should WAKEUP the BLE Chip first, or it will be messy code. In the low power consumption mode, if there is no extra operation, Bluetooth will enter this mode after 10s. You can awake Bluetooth by interruption pins; awake ATmega328P by Bluetooth:

Wireless Programming

Bluno 2 wireless programming is completely compatible with Bluno1 (BLE4.0). And it is only available under P2P connection mode: the host (the central device) to the slave side.

Firmware Upgrade

DFRobot BLE4.1 has the firmware method to BLE 4.0, click to download BLE4.1 firmware update tool, BLE4.1 firmware address Firmware Download

Fig1: Bluno2 Firmware Update Tool

Update steps are as below:


Q&A Some general Arduino Problems/FAQ/Tips
Q How to deal with the situation cannot download?
A There are many reasons for this problem:
1. Check basics, such as power supply, board type and COM port.
2. Bluetooth will occupy the serial port which will hamper uploading. Please disconnect the current Bluetooth connection, and try again.
3. The device serial port may be occupied. Please disconnect all peripherals then recompile and download again.
4. Arduino IDE may crashed. Please disconnect all Bluetooth (include smartphone), close all Arduino IDE software, pull USB line, reopen and test.
5. Bootloader in the FireBeetle 328P may get lost. Please try re-uploading Bootloader of ATmaga328p.
6. BLE 4.1 firmware may wrong. Please re-upload firmware and check the former chapter for reference.
Q: How to choose board when the device manager shows Arduino UNO COM x after connected to PC?
A The COM name in default is Arduino UNO. Please choose the board according to bootloader, e.g. choose Arduino Pro Mini 3.3V@8MHz for FireBeetle BLE4.1.
Q: How to deal with the Bluetooth ID number varies with connection?
A: The current Bluetooth ID number is defined with the connection order, ID1, ID2, ID3, DI4 in order and unchangeable. Please connect the host (the central device ID0) in turn.
Q: Why the Bluetooth data been received is gibberish in the baud rate 115200?
A: The bootloader that FireBeetle BLE4.1 uses is 3.3V Pro Mini of 8MHz oscillator. The Arduino Pro Mini 3.3V@8MHz may runs wrong with high baud rate. The lower baud rate is recommend, e.g. 9600bps
Q: Does BLE4.1 supports HID, ibeacon and tree network?
A: The functions HID, ibeacon and tree network are under development.

For any questions, advice or cool ideas to share, please visit the DFRobot Forum.

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