GC40 is a low-power Bluetooth (BLE) module based on a cost-effective System-on-Chip (SoC). It supports Bluetooth 4.0.

Overview

  • Voltage range: 2.0 V to 3.6 V (typical 3.3 V)
  • Frequency range: 2402 MHz to 2480 MHz (programmable)
  • Modulation: GFSK
  • Data rate: 1 Mbps
  • Operating temperature: -30 °C to 85 °C
  • Dimensions: 18.8 mm × 15.1 mm
  • Antenna impedance: 50 Ω
  • Antenna: PCB antenna (on-board)

Applications

  • 2.4 GHz low-power Bluetooth systems
  • Mobile phone accessories
  • Sports and leisure equipment
  • Consumer electronics
  • Human-computer interaction devices (keyboard, mouse, remote)
  • USB transceiver dongles
  • Healthcare and medical devices

Electrical and RF Specifications

Parameter Value
Supply voltage 2.0 V – 3.6 V (typical 3.3 V)
Operating frequency 2402 MHz – 2480 MHz (programmable)
Frequency accuracy ±20 ppm
Modulation GFSK
Data rate 1 Mbps
Max TX power 7.9 dBm (programmable)
RX sensitivity -94 dBm
Sleep current 8 μA
RX current 12 mA
TX current 20 mA (at 7.9 dBm)
Typical range 100 m (open space)
Operating temperature -30 °C – 85 °C
Size 18.8 mm × 15.1 mm

Pin Definitions

No. Pin Type Description
1 VCC Power Power input, 2.0 V – 3.6 V (typ. 3.3 V)
2 GND Ground Connect to GND
3 UART_RX Digital I/O UART receive
4 UART_TX Digital I/O UART transmit
5 OUTPUT_IND Digital I/O Data output indicator: outputs a 460 μs low pulse before UART data is sent
6 CONN_IND Digital I/O Connection status indicator: HIGH after reset, LOW when a BLE connection is established
7 WAKEUP Digital I/O WAKE pin: in low-power mode pull this low to enable UART communication (see note)
8 GPIO0 Digital I/O Configurable as input or output
9 GPIO1 Digital I/O Configurable as input or output
10 GND Ground Connect to GND
11 GND Ground Connect to GND

Schematic

Indicator & Wake Behavior

  • After reset, the module's CONN_IND pin outputs a HIGH level. When a Bluetooth connection is established, CONN_IND goes LOW.
  • After a connection is established, when the module receives a BLE data packet, OUTPUT_IND will first output a 460 μs low pulse to notify the external MCU that data will be sent, and then the module transmits the data over UART.
  • In low-power mode the external MCU must pull WAKEUP low for at least 10 μs to wake the BLE module before sending UART data.

AT Commands

Notes:

  • All commands and responses use ASCII.
  • Each command must end with (carriage return + line feed) unless otherwise noted.
  • If a command is accepted the module responds with the appropriate reply (OK or the requested data); otherwise it responds with: ERROR.

1) Mode switch (command/transparent modes)

  • Default after power-up: transparent (data) mode. To enter command mode after power-up, send: AT+MODE=0.

Examples:

  • Query current mode: Send: AT+MODE
    • Response: +MODE:
      • para = 0 (command mode) or 1 (transparent/data mode)
  • Query supported parameters: Send: AT+MODE?
    • Response: +MODE:
      • para = 0,1
  • Set mode: Send: AT+MODE=
    • para = 0 or 1
    • OK on success; ERROR on failure

2) Advertising (scan) enable

  • Default: advertising enabled.

Examples:

  • Query current advertising state: Send: AT+SCAN
    • Response: +SCAN:
      • para = 0 (advertising disabled) or 1 (advertising enabled)
  • Query supported parameters: Send: AT+SCAN?
    • Response: +SCAN:0,1
      • (0 = disable advertising; 1 = enable advertising). This setting only applies when the module is not connected.
  • Set advertising state: Send: AT+SCAN=
    • para = 0 or 1
    • OK on success; ERROR on failure

3) Connection interval (link interval)

  • Supported range: 10 ms to 2000 ms, in 10 ms increments. Changes take effect immediately.

Examples:

  • Query current interval: Send: AT+LINKINV
    • Response: +LINKINV: (current interval in ms)
  • Query supported parameters: Send: AT+LINKINV?
    • Response: +LINKINV:
  • Set interval: Send: AT+LINKINV=
    • para = multiple of 10 (ms)
    • OK on success; ERROR on failure

4) UART baud rate

  • Default: 9600, 8N1.
  • Supported baud rates: 9600, 19200, 38400, 57600, 115200.

Examples:

  • Query current baud: Send: AT+UART
    • Response: +UART: (current baud)
  • Query supported rates: Send: AT+UART?
    • Response: +UART:
  • Set baud: Send: AT+UART=
    • para = 9600,19200,38400,57600,115200
    • OK on success; ERROR on failure

5) TX power configuration

  • Ten levels available:
Level TX Power (dBm)
0 -19.5 dBm
1 -16.0 dBm
2 -13.3 dBm
3 -9.6 dBm
4 -5.0 dBm
5 -3.1 dBm
6 0.0 dBm
7 3.3 dBm
8 6.3 dBm
9 7.9 dBm (default)

Examples:

  • Query current power: Send: AT+RFPW
    • Response: +RFPW:
  • Query supported values: Send: AT+RFPW?
    • Response: +RFPW:
  • Set power level: Send: AT+RFPW=
    • para = 0..9
    • OK on success; ERROR on failure

6) Module name

  • Default name: GCBT40. Maximum length: 18 bytes. Changes take effect after reboot.

Examples:

  • Query name: Send: AT+NAME
    • Response: +NAME:
  • Set name: Send: AT+NAME=
    • para = new name (up to 18 bytes)
    • OK on success; ERROR on failure

7) Advertising interval

  • Supported values: 100, 200, 500, 1000, 2000 (ms). Range: 100 ms to 2000 ms. Changes while advertising take effect immediately.

Examples:

  • Query current advertising interval: Send: AT+ADVT
    • Response: +ADVT:
  • Query supported values: Send: AT+ADVT?
    • Response: +ADVT:
  • Set advertising interval: Send: AT+ADVT=
    • para = 100,200,500,1000,2000
    • OK on success; ERROR on failure

8) Query MAC address

  • Send: AT+GMAC
    • Response: +GMAC: (MAC address)

9) Low-power (standby) modes

  • Default: normal mode.

Examples:

  • Query standby mode: Send: AT+STBY
    • Response: +MODE:
      • 0 = normal mode
      • 1 = low-power mode
  • Query supported parameters: Send: AT+STBY?
    • Response: +MODE: (para = 0,1,2)
  • Set standby mode: Send: AT+STBY=
    • para = 0,1,2
    • Mode 2 = deep sleep: after wake the module auto-resets and mode returns to the previous 0 or 1
    • OK on success; ERROR on failure

10) RF test (single-carrier transmit)

  • Send: AT+TEST=P,C
    • P = TX power level (0..9)
    • C = channel index; frequency = 2402 + C*2 MHz
    • OK on success; ERROR on failure

11) Restore factory defaults

  • Send: AT+DEFA
    • Response: OK
    • The module will automatically reboot after this command

BLE Services and Characteristics (Commands)

Below is a concise, developer-friendly summary of the module's BLE services and characteristics. All UUIDs are 16-bit.

1. Data Services (Service UUID: 0xFF10)

Characteristic UUID Properties Length Function
Bluetooth data channel 0xFF11 Write 20 bytes Data written here is forwarded to the UART output
UART data channel 0xFF12 Notify 20 bytes Data from UART is sent to the connected mobile device via notifications

2. Configuration Service (Service UUID: 0xFF20)

Characteristic UUID Properties Function / Notes
Connection interval config 0xFF21 Write Configure connection interval; supported in multiples of 10 ms. Write the corresponding value to set. On success the status channel returns OK; otherwise ERROR. Query: send '=' to read current config (reply via status channel). Send '?' to query supported values.
Rename module 0xFF22 Write Set module name (max 18 characters). Reboot required to apply.
UART baud rate config 0xFF23 Write Supported baud rates: 9600, 19200, 38400, 57600, 115200. Query: send '=' to read current value; send '?' to read supported values.
TX power config 0xFF24 Write Power levels 0–9 (see table below). Default is level 9 (7.9 dBm). Query: '=' current, '?' supported.
Low-power mode enable 0xFF25 Write 0 = normal mode, 1 = low-power mode. Query supported values with '?'.
Advertising/connection interval 0xFF26 Write Supports multiples of 10 ms. Write value to set. Query: '=' current, '?' supported.
Status reply (operation result) 0xFF2F Notify Returns status for configuration operations. Query replies return the requested data; config operations return OK or ERROR.

TX power levels mapping (level -> dBm):

Level TX Power (dBm)
0 -19.5 dBm
1 -16.0 dBm
2 -13.3 dBm
3 -9.6 dBm
4 -5.0 dBm
5 -3.1 dBm
6 0.0 dBm
7 3.3 dBm
8 6.3 dBm
9 7.9 dBm (default)

3. GPIO Control Service (Service UUID: 0xFF50)

Characteristic UUID Properties Function
GPIO0 output control 0xFF51 Write Write 0 or 1 to set GPIO0 output
GPIO0 mode control 0xFF52 Write 0 = input mode, 1 = output mode
GPIO0 status 0xFF53 Read Read GPIO0 state: 0 = low, 1 = high
GPIO1 output control 0xFF54 Write Write 0 or 1 to set GPIO1 output
GPIO1 mode control 0xFF55 Write 0 = input mode, 1 = output mode
GPIO1 status 0xFF56 Read Read GPIO1 state: 0 = low, 1 = high
Data storage 0xFF58 Read/Write Read or write up to 18 bytes for persistent storage (retained after power loss)
GPIO status notification 0xFF5F Notify Notifies external device of GPIO status changes

4. Device Information Service (Service UUID: 0x180A)

Characteristic UUID Properties Length Default / Notes
Module MAC address 0x2A23 Read 8 bytes Default: 0000xxxxxxxxxxxx (hex); physical address of the module
Module model 0x2A24 Read 15 bytes Default: GC40
Software version 0x2A28 Read 4 bytes Software/firmware version
Manufacturer 0x2A29 Read 10 bytes Default: "BLE Module"

Notes and Usage Tips

  • Use the OUTPUT_IND pulse to synchronize reads from UART if the host MCU sleeps or polls.
  • Before sending UART data while the module is in low-power mode, pull WAKEUP low for at least 10 μs.
  • After changing configuration values that require a reboot (for example the module name), cycle power or issue a software reboot to apply changes.

ref

Table of Contents

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