HC-05/06 AT Command Center

Arduino library for simplifying AT command configuration of HC-05/06 devices over UART.

Version 2.0

Overview

Description: Simple HC05/06 AT configuration library for Arduino. Requires 2nd UART (Serial1) defined. Full repo can be found at HC06_AT_CommandCenter. Reference site for this library can be found here.

Provides user menu for selecting configuration changes. Automatically identifies device (HC-05 or HC-06), firmware version, baud and parity settings. Serial1 automatically configured to match HC-05/06 UART settings. HC-05/06 must be in configuration mode (AT mode) (LED blinking to indicate Not Connected).

HC06 connections (for 5V boards - resistors not needed for 3V3):

            TXD -----------------> [Serial1 RX]
            RXD <----+---R_1K----- [Serial1 TX]
                     |
                     |
                   R_2K
                     |
                    \|/
                    Vss

HC05 connections: same as above, but also include (for AT mode selection):

            STATE  -----------------> [State pin]
            EN/KEY <----+---R_1K----- [Mode pin]
                        |
                        |
                      R_2K
                        |
                       \|/
                       Vss

Command mode (AT mode):

Device LED should be blinking fast (> 2 Hz) when in command (AT) mode.

When LED is solid, device is paired and connected.

If LED is blinking slowly (HC-05), device is in fixed AT mode. In this mode, UART baud rate is fixed at 38400 with no parity. This occurs when EN/KEY pin is tied HIGH while power is connected. For this reason, [Mode pin] will be set to INPUT mode when not communicating AT commands. If LED is blinking slowly, try disconnecting and reconnecting power to HC-05 device.

Pin connections:

                board        Mega    MKR   Uno WiFi  Zero    Due    MSP432
  -------------------+-------------------------------------------------------
    [Serial1 RX]     |        19      13      0        0      19       3 
    [Serial1 TX]     |        18      14      1        1      18       4 

Recent batches of HC-06 appear to have HC-05 firmware (reporting Version 3). There is no documentation of a Version 3 firmware for HC-06. AT commands differ for HC-05 firmware, including CR+NL command terminators. Support for this version has been added beginning with Revision 1 of this software.

AT response delays:

Around 10~25ms for Version 3.x (newline terminated) - max observed 35ms

Around 500ms for Version 1.x (timeout terminated) - max observed 525ms

Serial writes are asynchronous, so delays must also consider write time

History

  Created on: 18-Oct, 2021
  Author: ndroid (miller4@rose-hulman.edu)

    Modified: 09-Oct, 2023
    Revision: 2.0.1
            * corrects UART failure following detectDevice() failure (Issue #6)
    Modified: 25-Sep, 2023
    Revision: 2.0
            * added support and auto-detection for HC-05
            * defined classes for interfacing HC-0x devices
    Modified: 22-Apr, 2023
    Revision: 1.0
            * added support and auto-detection for firmware versions
                1.x and 3.x
    Modified: 24-Apr, 2022
    Revision: 0.4
            * added option to auto-detect firmware version and UART 
                configuration
    Modified: 7-Feb, 2022
    Revision: 0.3
            * updated end-line characters to support devices with newer
                firmware (3.0+) HC-05 firmware?
    Modified: 30-Jan, 2022
    Revision: 0.2
            * provides user menu for selecting desired configuration

License

Up to version 0.4.0, the license is GPLv3. From version 1.0.0, the license is the MIT license.

Copyright

Copyright (c) 2021-2023 chris miller (https://github.com/ndroid)