Arduino Two-Way Bluetooth with HC-05 module

Today we are going to learn how to establish two-way Bluetooth communications between an Arduino board and a PC. We will learn how to send data from the PC to the Arduino and from the Arduino to the PC using Bluetooth. In this step-by-step tutorial you will learn the basics of Bluetooth communications using the cheap and widely available HC-05 Wireless Bluetooth RF Transceiver Module.

HC-05 Bluetooth modules

The HC-05 is a Bluetooth V2.0+EDR (Enhanced Data Rate) SPP (Serial Port Protocol) module with 2.4GHz radio transceiver and baseband, designed for transparent wireless serial connection setup. It uses the CSR Bluecore 4-External single chip Bluetooth (BCR417) system with CMOS technology and AFH (Adaptive Frequency Hopping). It has a footprint as small as 12.7mmx27mm (without breakout board).

We must pay attention when buying these modules because there are several “flavors” of HC-05 Bluetooth modules. These modules cost about 5 USD and are available with or without a breakout board. The breakout board is a small “motherboard” where the Bluetooth module is soldered. Modules with a breakout board have a pin header, a led and sometimes also a button. Most HC-05 modules with breakout boards have also a voltage converter and can be powered from the Arduino 5V pin.

I recommend getting a version of HC-05 with a breakout board, because it’s much easier to work with when you are experimenting or testing. The most popular HC-05 modules appear to be the FC-114 and the ZS-40.

HC-05 Bluetooth module specs:
Bluetooth V2.0+EDR.
Typical -80dBm sensitivity.
Up to +4dBm RF transmit power.
Integrated antenna.
I/O: 1.8 to 3.6V.
PIO control.
UART interface with programmable baud rate.
Supported baud rates: 9600,19200,38400,57600,115200,230400,460800.
Auto-connect to the last device on power on as default.
Permits pairing device to connect as default.
Auto-reconnect in 30 min when disconnected as a result of beyond the range of connection.
Full HC-05 specs are available here.

All HC-05 modules seem to be using 3.3V logic level. Since most Arduino boards use 5V logic level, we need to use a logic level converter between the Arduino and the HC-05 module RX pin to convert 5V to 3.3V. We can use a level converter board or a simple 2 resistor voltage divider. In this tutorial I will use a 2 resistor voltage divider. There is no need to use a converter for the HC-05 TX pin because the Arduino works OK with the HC-05 3.3V logic.

Parts
Arduino UNO (others can be used)
HC-05 Wireless Bluetooth RF Transceiver Module
1x10K resistor
1x 22K (or 20K) resistor
Breadboard + Jumper wires

Step 1 – Connect the modules according to the circuit. 

Pay special attention to the supply voltage used by your module. If your HC-05 module uses 3.3V supply voltage you must connect it to the 3.3V pin on the Arduino, never the 5V. If you use excessive voltage you can destroy the module! 

The voltage divider is made with one 10K resistor and one 22K resistor, but you can use other values as long R2 is about 1/3 the sum of R1+R2. 

The HC-05 EN and STATE pins are not needed for this tutorial and are not connected. 

Step 2 – Power the Arduino board 

Apply power to the Arduino board by connecting to an USB connector on your PC or by connecting a power supply to the Arduino board DC input. The HC-05 module led should blink at a fast rate, signalling it is in data mode.

Step 3 – Pair the HC-05 Bluetooth module
Once the Bluetooth module is powered, it should be visible by other Bluetooth enabled devices like a cell phone, tablet or PC. For this tutorial we need the Bluetooth module to be detected by the PC, so your must enable or install a Bluetooth device (like a USB dongle). When Bluetooth is enabled the Bluetooth icon is shown in the O.S. system tray area. Click on it and select Add Devices. Your bluetooth module should be listed , usually as “HC-05”, click on it and then click Next. You will be prompted to enter the pairing code/password. The default code for most Bluetooth devices is either 1234 or 0000. Click Next. If the pairing is successful, you will see a confirmation message.

Remember that Bluetooth class 2 devices have a maximum range of about 30 ft (10m), but often reliable communication can only be made at distances shorter than 9 ft (3 m).

Step 4 – Upload the sketch file 

After the HC-05 module is paired, disable it by disconnecting from the power supply pin, otherwise you may not be able to upload the sketch. The project includes two files send_test and receive_test that can be downloaded from here. Open the send_test sketch on the Arduino IDE and upload it to the Arduino board. Once the upload is finished, reconnect power to the HC-05 Bluetooth module. 

Step 5 – Check if the Bluetooth module is transmitting 

The code on the send_test sketch will repeatedly send a text message via Bluetooth. Open a terminal program like RealTerm and check that this message is being received. Don’t forget to set the correct port and baud rate. The default baud rate for the HC-05 module is 38400. If you see garbled characters instead of text, you are most probably using the wrong baud rate. The ports being used can be seen on your PC’s device manager. RealTerm can be downloaded here.

Step 6 – Check the Bluetooth module is receiving 

Disconnect power to the Bluetooth module. Open the receive_test sketch on the Arduino IDE and upload it to the Arduino board. This code will make the led on the Arduino board turn ON or OFF when you send 1 or 0 from the terminal program. Once the upload is finished, reconnect power to the HC-05 Bluetooth module.

Press the Send tab in RealTerm, type 1 and press the Send as text button. The led on the Arduino board should turn ON. Now type 0 and press the Send as text button. The led on the Arduino board should turn OFF. 

That’s it for now! We successfully tested bi-directional Bluetooth communication between the Arduino and a PC. Next time we will learn how to read and change default HC-05 Bluetooth module settings. 

Buy the parts
Buy the Arduino UNO from Banggood
Buy the HC-05 Bluetooth module from Banggood
Buy resistors from Banggood
Buy the Arduino UNO from Dealextreme
Buy the HC-05 Bluetooth module from Dealextreme
Buy resistors from Dealextreme

I may get a small fee if you use the links to buy the parts. Thank you for your support!

ESP8266 NodeMCU firmware update

As we know from previous posts, the ESP8266 WiFi module can work as a standalone device. It's MCU, GPIO ports and user memory are all it's needed to make simple IoT projects like wireless Internet enabled data loggers.

For the ESP8266 to work as a standalone device we need to use a module with bootable OS. For this project we will use the NodeMCU firmware. NodeMCU is a firmware based in the eLua programming language for the ESP8266 from Espressif. The latest firmware is based on the Espressif NON-OS SDK 1.5.1.

You can buy a ESP8266 module with NodeMCU already loaded or you can flash a "standard" ESP8266 with the NodeMCU firmware yourself. If you're like me you'll want to flash the firmware yourself. After all that's how we learn stuff, by doing it ourselves!

NodeMCU firmware can be obtained from GitHub. It currently is made up of 41 modules. According to the team, due to the ever-growing number of modules available within NodeMCU, pre-built binaries are no longer made available. Now you select the modules you need, provide an e-mail address and the firmware will be custom built and sent to your e-mail. But older pre-built NodeMCU firmware versions are available. You can also built your own NodeMCU firmware. Fore more info go to the NodeMCU firmware GitHub project page.

To replace the ESP8266 firmware with NodeMCU we can use one of several flasher tools available. I will use the official tool from Espressif: ESP Flash Download Tool. 

Put the ESP8266 module in download mode and download the NodeMCU .bin firmware file to the 0x00000 address. You will need an USB to Serial adapter. If you don't know how to do this, read my previous post.

After the the firmware is successfully uploaded to the module we can check if the device is booting with NodeMCU. Disable download mode, start RealTerm and restart the module. In RealTerm you shoud get a Lua prompt:

Ignore the cannot open init.lua message, it's normal. It's shown because we did not upload a init.lua file yet. We'll do that when we upload Lua project files.

Downloads:
Download ESP FLASH DOWNLOAD TOOL
Download ESP8266 NodeMCU firmware
Download RealTerm

Buy the Parts:
Buy the ESP8266 Wi-Fi from Banggood
Buy the ESP8266 Wi-Fi from Dealextreme
Buy the USB to Serial Adapter from Banggood
Buy the USB to Serial Adapter from Dealextreme

Previous ESP8266 posts: 
ESP8266 firmware update
ESP8266 ESP-01 testing - Part 2
ESP8266 ESP-01 testing - Part 1
ESP8266 WiFi modules

ESP8266 firmware update

If you have one or more of these little ESP8266 WiFi modules, sooner or later you will want to update their firmware. Espressif, the module's maker has been regularly releasing firmware updates introducing new functionalities and bug fixes. So, let's give it a try!

In previous posts I demonstrated how to connect the ESP8266 to a computer and test it. You may want to check it out if you don't yet know how to do that. Check the shortcuts at the end of this post.

Which firmware?

You can choose between firmware's with OS or without OS (NONOS). A firmware with OS will make your module a bootable device able to work by its own. You can even develop and upload a customized firmware. There are firmware's from different sources spread across the Internet, some quite suspicious. I recommend to go with a "trusted" source like AI-Thinker or Espressif. For this guide I will be using firmware from Espressif, the maker of the modules.

I am using a 4Mbit module and, at the time of writing, the latest firmware from Espressif that will "fit" this memory size is esp8266_nonos_sdk_v1.4.0_15_09_18_0. If your module has 8Mbit flash or more, you can update to a newer version. You can download ESP8266 firmware from Espressif here.

What firmware flasher tool?

To upload the firmware to the ESP8266 we can use several programs. I will be using the free ESP FLASH TOOL from Espressif, the maker of the modules. The latest version is 2.4, you can get it here.

Firmware download mode

Before the firmware can be uploaded, the ESP8266 module must be in firmware download mode. This is done by connecting GPIOØ pin to ground (GND).

Get ESP8266 module info

Once the module is in download mode, powered up and connected to a computer:

• Check the correct COM port is selected in ESP FLASH TOOL. The default Baud rate should work. In case it doesn't try different values.
• Click the START button.

The program should display SYNC in a green square left of the start button. It will retrieve the MAC address, memory size and crystal frequency, among other info. .

Select and upload firmware files

Now that we know the ESP flash download tool is communicating with our module:

• Select the correct flash memory size and crystal frequency. Note: sometimes the program retrieves a wrong crystal frequency (24Mhz or 21Mhz for example).

Now, depending on the firmware we want to use, we need to select one or more files in the ESP Flash Download Tool Download Path Config panel. Each of these files must be loaded to the correct memory address. This information should be in a Readme file in the firmware archive file.

• For each file needed, click the ... button of the correct memory address and navigate to the .bin file.

• Check the selection box of each file/memory address.

• Press START.

After a few seconds, if the upload was successful, the ESP Flash Download Tool will display FINISH.

Now that we successfully updated the firmware we must not forget to disable the firmware download mode by disconnecting the GPIOØ pin from ground!

In RealTerm, sending the AT+GMR command will show the new firmware info: 

Be aware that the firmware upgrade might change the ESP8266 baud rate. In this case you must change the baud rate in RealTerm also!

I have uploaded a ESP8266 firmware upgrade video tutorial to YouTube. Please check it out and give it a thumbs up if you like it!

Downloads:
Download ESP FLASH DOWNLOAD TOOL
Download ESP8266 firmware
Download RealTerm

Buy the Parts:
Buy the ESP8266 Wi-Fi from Banggood
Buy the ESP8266 Wi-Fi from Dealextreme
Buy the USB to Serial Adapter from Banggood
Buy the USB to Serial Adapter from Dealextreme

Previous ESP8266 posts: 
ESP8266 ESP-01 testing - Part 2
ESP8266 ESP-01 testing - Part 1
ESP8266 WiFi modules

ESP8266 ESP-01 testing - Part 2

Today we are going to learn how to communicate with the ESP8266 module through the serial (UART) connection using AT commands. 

In the previous post we learned how to connect the ESP8266 to a computer and test the serial and WIFI connection. If you need help hooking up your ESP8266 module take a look here: ESP8266 ESP-01 testing - Part 1

AT commands

Serial communication with the ESP8266 is done using AT commands. If you are not familiar with AT commands, they are instructions used to control modems. The ESP8266 is controlled the same way as a modem or GPS module. An instruction (or command) request is sent to the device to perform an action that once evaluated is executed (or not) and a "response" is given in return. The ESP8266 accepts many AT commands but today we are only going to use some of the most common ones. A full list of ESP8266 AT commands is provided at the end of this post.

The board used in this tutorial uses the stock firmware version .9.0.2 (00180008902) from AI-Tinker.com. Different firmware versions may behave differently. The AT commands list has also been updated since these boards where launched. If you are using a board with older firmware version and/or older AT commands version, newer AT commands will not be recognized! Like with firmware, the ESP8266 board AT list can be updated.

Let's get started!

Test AT startup

The first command we are going to send to the ESP8266 board is simply AT. It's used to test the startup function of our ESP8266 module. In RealTerm:

1. Click the Send tab.
2. Type AT in the first textbox.
3. Check the  +CR and +LF.
4. Press the Send ASCII button.

The ESP8266 board should respond with an OK message. This tells us the command was received and the serial communication is ready and working.

View version information

Now lets find out what is the firmware version of our ESP8266 board. Send the AT+GMR command.

This board uses firmware version .9.0.2 (00180008902). This is an old firmware version.

Note: the version information displayed depends on the firmware running on the board. Newer firmware versions display the firmware version and the AT commands version.
 

Change baud rate

Lets change the ESP8266 baud rate, or the speed of the serial communication. Let's try 115200 baud. Type AT+CIOBAUD=155200 and press the Send ASCII button. The ESP8266 should output the following text which confirms the new baud rate was accepted:

Notes:
Newer boards accept two sets of serial parameters: AT+UART_DEF (default params, saved on the board memory) and AT+UART_CUR (current params, not saved).

Now the ESP8266 serial interface is running at 115200 baud. Since we changed the baud rate in the ESP8266 module we must also change the baud rate in RealTerm to 155200!

The new baud rate was set and stored in the ESP8266 memory. From now on, every time the board is started or restarted it will default to 115200 baud rate. 

We can also ask our ESP8266 module what the baud rate is. To do this we send the command AT+CIOBAUD?  

Other AT commands you might want to test:

AT+RST – Restart module;
AT+RESTORE – Factory reset.

Wi-Fi related AT commands

Before trying out WiFi commands we should get familiar with the different WiFi modes. As we know, the ESP8266 supports three modes: station mode, softAP (virtual access point) mode and station mode + softAP mode. In station mode the ESP8266 works as a network device and can connect to an existing wireless network (router). In softAP mode the ESP8266 behaves as a wireless router and can be connected to by network devices.When operating in both modes (softAP + station mode), the ESP8266 can act as network repeater.

Set WiFi mode

The default ESP8266 WiFi mode is softAP (2). To know what mode your ESP8266 module is in, send the command AT+CWMODE?

According to what WiFi mode the ESP8266 is on it will respond with 1 : station mode, 2 : softAP mode or 3 : softAP + station mode.

To set to a particular WiFi mode send AT+CWMODE=X, where X is the mode you want to set.

To use the next WiFi commands the ESP8266 must be in mode 1 or mode 3, so change to station mode (mode 1), sending  AT+CWMODE=1.

Note:
AT+CWMODE will not be recognized by boards with firmware from Espressif, use AT+CWMODE_CUR or AT+CWMODE_DEF instead.

Get list of available WiFi access points in our location

Type and send the command AT+CWLAP. The  ESP8266 will scan the WiFi frequency range and list all the access points in range. Each line item consists of the security level of the AP, network name, signal strength, MAC address and WiFi channel.

Security Modes:

0	Open
1	WEP
2	WPA_PSK
3	WPA2_PSK
4	WPA_WPA2_PSK

Note:
If the you get an AT+CWLAP ERROR set the ESP8266 to station mode or softAP + station mode.

Join access point

To join an access point we can use the command AT+CWJAP="SSID","Password".SSID is the

After a few seconds the ESP8266 should respond with OK if successful or FAIL if unsuccessful. After the board joins an access point, it will store that AP SSID and password and automatically join that access point every time the board starts up! To stop this, simply disconnect from the AP before powering of the board.

Note:

This command has been deprecated. If your board uses firmware from Espressif use AT+CWJAP_CUR or AT+CWJAP_DEF instead. See the Espressif ESP8266 AT commands list for details.

Disconnect from AP

To disconnect our ESP8266 from an access point simply send the AT+CWQAP command.


Documentation and tools:
Download RealTerm here.
Download AI-Thinker AT commands list here (unofficial).
Download Espressif ESP8266 AT commands list here.

Buy the Parts:
Buy the ESP8266 Wi-Fi from Banggood
Buy the ESP8266 Wi-Fi from Dealextreme
Buy the USB to Serial Adapter from Banggood
Buy the USB to Serial Adapter from Dealextreme

NEXT: ESP8266 firmware update
PREVIOUS: ESP8266 ESP-01 testing - Part 1

ESP8266 ESP-01 testing - Part 1

In this post I'm going to test the ESP8266 ESP-01 WIFI module. I will demonstrate how to perform simple tests of the WIFI signal and serial communications with the module. This enables you to quickly check if  a board is good or faulty.

The previous post was and introduction to the ESP8266 WIFI modules family. If you missed it, you can read it here: ESP8266 WIFI modules.

Let's get started!

The ESP8266 ESP-01:

This module has inbuilt pcb antenna, 2 GPIO ports and pin header for external connections. Signal range is up to 400 meters (in open range). The board measures 14.3mm x 24.8mm. Prices start at around 2 USD for a ESP-01 with 4Mbit RAM memory (8Mbit RAM is also available).

The ESP-01 module used for testing is made by AI-Thinker.com, but the testing procedures are identical for boards from other vendors.

Testing the ESP8266:

When you buy one of these WIFI marvels you will want to perform a quick test to see if you received a good working device. 

Testing the WIFI

The simplest test is to power the module and check if its WIFI signal is detected. 

Connect the ESP-01 to a 3.3 Volts power source (GND and VCC pins). The module draws up to 170 mA when transmitting, so any power source capable of 170 mA will do the job.

 

WARNING: The ESP8266 power supply (Vcc) requires 3.0v to 3.6v. Never connect it to 5 Volts! 

After a few seconds your ESP8266 module should be listed as ESP_XXXXXX.

Testing the serial connection

Now we are going to test the wired serial communication between the ESP8266 and your computer. To do this we need to to connect the ESP8266 ESP-01 to a computer using the serial connection (UART) and a USB to serial adapter.

Connect the USB to serial adapter to the computer and check that it is recognized by the O.S. If you are connecting the adapter to the computer for the first time, you may need to install drivers. After the adapter connects successfully, disconnect it from the computer.

Since the ESP-01 board communicates using 3.3 volt logic levels and not the more common 5V most adapters use, we will also be using a logic level converter. If your serial to USB adapter supports 3.3v logic level then you do not need the level converter (or level shifter). Do not confuse UART logic level voltage with power supply voltage!

Connect the USB to serial adapter, level adapter and ESP8266 module as follows:

Most USB to serial adapters either have a jumper to set the power supply line (VCC) to 5V or 3.3V or have separate 5V and 3.3V VCC pins. Some level converters also have a 5V to 3.3V voltage converter. You can set the power to 3.3V in USB to serial adapter and connect it to the ESP8266 module or, you can connect the 5V Vcc output from the serial to USB adapter to the 5V Vcc of the level converter and connect the 3.3V output of the level converter board to the VCC pin of the ESP8266.

Please note that it IS possible to successfully connect the ESP-01 to the serial to USB adapter without the level converter/shifter, but doing so may cause unreliable operation or damage the ESP8266 board!

And this is how it may look after the connections are made. The small breadboard is not essential but, since we need to connect the ESP8266 CH_PD pin to a high logic level (3.3V), it is very handy.

To "talk" to the module we can use several serial communication / terminal programs or even the Arduino IDE. I will demonstrate using RealTerm. Realterm is free and can be downloaded from sourceforge.

After installing RealTerm, double check the boards connections and connect the serial to USB adapter to your computer. The red led (power) on the ESP8266 board should light up. The blue led should blink briefly. If the leds don't light up, unplug the USB to serial adapter from the computer immediately and check the connections again.

In the RealTerm Port tab, check if the correct port is selected. You can check this in the O.S. device manager COM ports. Make sure that byte size, parity and flow control are the same as the following image.

Disconnect and reconnect the CH_PD connection, preferably in the breadboard. Some readable text, like vendor name and firmware version should be displayed. 

If only garbled text is displayed it means RealTerm is not communicating correctly with the module. This probably caused by a speed mismatch. Select a different baud rate, press the Change button and disconnect and reconnect the CH_PD again. Repeat this until some legible text is displayed. Most modules seem to come with a default baud rate of 9600, so you may want to try 9600 baud first. 

That's it for now! Next time we will learn how to send commands to the ESP8266 module and, amongst other things, change the baud rate (speed) of our board. 

Documentation and tools:
Download RealTerm here.
Download ESP8266 datasheet here.
Further ESP8266 information, documentation and tools available on the Espressif Systems site. 
List of ESP8266 modules and specifications of  ESP8266 modules from AI-Thinker (not full list) can be downloaded here.

Buy the Parts:
Buy the ESP8266 Wi-Fi from Banggood
Buy the ESP8266 Wi-Fi from Dealextreme
Buy the USB to Serial Adapter from Banggood
Buy the USB to Serial Adapter from Dealextreme

NEXT: ESP8266 ESP-01 testing - Part 2
PREVIOUS: ESP8266 WiFi modules