Tag Archives: mission planner

Change the baud rate of HC-05 Bluetooth module

If you want to change some of the settings of your HC-05 Bluetooth module, like baud rate, password or the name of the Bluetooth module, you can do it easy and fast with your Arduino. I have done this to connect my Pixhawk to DroidPlanner over Bluetooth.

There are different HC-05 modules on the market, but it should work with all of them. On the picture below you can see a bare HC-05 module, 5V tolerant HC-05 module and 6V tolerant HC-05 module with a button. I prefer the last one, as the button makes the changing of the settings even easier.


To change any settings of the module, it should be in the so called “AT Mode”. How to put the Bluetooth module in AT Mode: The “Key Pin” of the module should be set to “High”. This means we should apply voltage to this pin at the same time we power the module. On the last module, the button does this job. It should be pressed when powering the module with 5V. On the module without button, we need to supply 3.3V to the “Key Pin” when powering on.

Here is an example how to connect the module to the Arduino Nano v3. Note that there should be an jumper on GND and RST pin. By doing this, the Arduino will only act as a simple FTDI adapter.


First connect the Arduino to the PC over USB. Then connect the cables in the following way:

  • TX Bluetooth –> TX Arduino
  • RX Bluetooth –> RX Arduino
  • GND Bluetooth –> GND Arduino

… and at last the 5V Bluetooth to 5V Arduino by keeping the button of the Bluetooth pressed. Or on the module without button, connect the Key Pin Bluetooth to 3.3V on Arduino.

If the HC-05 is in AT Mode, the red LED will blink at every 2 seconds.

Then start the PuTTY program (download link), configure the right COM Port (Check it in the Device Manger) and set the Baud Rate to 38400. This is the baud rate for AT Mode. Then click “Open”.


In the newly opened black window type “AT”, press Enter and you should get “OK” as a result. Note that you want see what you type in the windows… Here some of the commands to change the settings you wish:

Change baud rate to 57600, 1 stop bit, 0 parity AT+UART=57600,1,0
Change module name AT+NAME=YOURNAME
Change pairing code AT+PSWD=0000

Voltage Sensor on HK Megapirate Multiwii AIO board

On my old KK2.0 board there was an integrated voltage meter. On the new KK 2.1.5 board there is even a header for the voltage detection. But on my new HK Megapirate Multiwii AIO there is no voltage sensor integrated at all. It is very important to know the voltage of the battery pack, so I decided not to buy a voltage sensor, but instead to build my own. I used a simple electric circuit of two resistors, a voltage divider. Very useful for me was this page: http://www.multi-rotor.co.uk/index.php?topic=3144.0

So I used this two resistors R1=110 kohm and R2=47 kohm (You can use resistors with other values, important is the ratio R1/R2). I also find this webpage very useful. After about 10 minutes and some soldering my voltage divider was ready. I connected it to the analog Pin0 on my Megapirate AIO and enabled the voltage sensor in Mission Planner. Then I needed to calibrate the voltage sensor. I used this very good manual on the ArduCopter official webpage. That’s it. Now I can check the voltage of my battery during flight using the Droid Planner 2 app on my smartphone.


Connecting Mission Planner over Bluetooth

I am using the MultiWii and MegaPirate AIO board (Crius clone) on my quadcopter since a few weeks. I had also a Bluetooth Module HC-05, which I bought for some Arduino projects. I wanted to connect the Mission Planner with my QuadCopter over Bluetooth using this module. I tried and followed the guides on Internet, but without success. Even the tip with first clicking the “Connect” button in Mission Planner and then powering on the HC-05 Bluetooth module didn’t helped me.

I did all the things right: Changed the default baud rate of my HC-05 with AT-Commands to 115200. In my APM_Config.h defined the baud rate of Serial0 to 115200. Connected and paired it with my PC. In Mission Planner chose the right COM port and the right baud rate of 115200. Without success… every time I tried to connect, I became “Getting Params” and then a “Connect failed” in Mission Planner.


Today I became another tip on a Bulgarian Hobby Forum: Not to use the Serial0 port, but the Serial3 port of my flight board. I defined the Serial3 port baud rate in my APM_Config.h, flashed it and connected the Bluetooth module with the Serial3 pins and for the GND and 5V with the Pins for the Camera Shutter.


Then I used the tip with first clicking the “Connect” button and connecting the power to the module, when the Mavlink Window appear on the screen. Few seconds and it WORKED. Problem solved. I still don’t know, why it don’t work over Serial0, but I am happy, that I can use my HC-05 Bluetooth with Mission Planner. So thanks again to the guy, that gave me this tip!

Update 21.04.2014: Here you can read on how to connect with the App DroidPlanner 2 over Bluetooth.

Update 01.05.2014: Mission Planner was updated to version 1.3.1. Since then you don’t need the trick with first clicking “connect” and then actually connecting the Bluetooth module anymore.