Is it possible to control an Arduino using mBlock and Bluetooth?

Assuming yes, I tried various things, but was not able to come to a conclusion.

I am trying to get this combination working using a HC-05 Bluetooth module. I am not sure if my Bluetooh setup is the problem or is mBlock is not able to recognize the COM port provided by Bluetooth.

I can see the COM device (in fact two?) when I pair HC-05 with PC. I have the following questions based on whatever I have tried so far:

  • When I connect HC-05, should I connect TX to TX OR reverse them?
  • There are varying articles describing both ways of connection.
  • How much baud rate do I need to set on the Bluetooth device?
  • Do I need to use the voltage divider for RX? Again there are varying tutorials.
  • Is mBlock default Arduino firmware sufficient for such setup?

2 Answers 2

  • When I connect HC-05, should I connect Tx to Tx OR reverse them?
    • There are varying articles describing both ways of connection.

Yes, swap them. TX on the HC-05 to RX on the Arduino. However you could struggle to use pins 0/1 since they are the USB connection. SoftwareSerial (which is nasty) is what most people use instead.

  • How much baud rate do I need to set on the bluetooth device?

Whatever rate you want to communicate at. It's up to you. However all baud rates must match throughout the system - the baud rate on the Arduino, the baud rate of the HC-05, the baud rate of the SPP port on your PC, etc.

  • Do I need to use the voltage divider for Rx? Again there are varying tutorials.

Which RX? Arduino TX to HC-05 RX yes. HX-05 TX to Arduino RX no.

  • Is mblock default arduino firmware sufficient for such a setup?

What is mblock?

  • thanks for the comments. mblock is the visual programmer tool which has arduino eco system integrated. mblock.cc. Jul 7, 2017 at 11:47
  • Majenko Could you please explain why using 0/1 is not good idea? I think the default firmware that I use for mblock may be expecting the serial communication to happen over 0/1 pin of arduino. Jul 7, 2017 at 12:14
  • 0/1 is used for communication with the PC and uploading new sketches. You can't do that whilst at the same time communicate with an external module such as bluetooth.
    – Majenko
    Jul 7, 2017 at 12:22

I got it working. Following are steps.

  • Set the Bluetooth baud rate to 115200. The mBlock firmware uses this baud rate for serial communication.
  • Connect Bluetooth to Rx and Tx of Arduino.
  • Upload default Arduino firmware (orion firmware) to Arduino using mBlock.
  • Use mBlock to interact with Arduino using Bluetooth.
    • Please note that Bluetooth cannot be used to upload the sketches to Arduino for offline mode.

Connecting Bluetooth COM device to PC in AT mode to set baud rate.

  • Upload empty (default) sketch to Arduino using USB cable.
  • Connect 5V of BT shield to 3.3V of Arduino.
  • Connect EN or BT to 5V.
  • Connect Tx to Tx and Rx to Rx.
  • Use USB cable to power on Arduino.
  • Before turning the power ON, keep pressing the EN button on BT shield. The LED should blink with almost a second delay. That is the indication that it is AT mode.
  • Start Arduino IDE, and connect to the COM port of Arduino and NOT that of the BT.
  • Start serial monitor.
  • Set the baud to 38400 and terminate character settings to "Both NL $ CR".
  • In the command input field of Serial Monitor type at twice. First time response will be error, second time it should be ok.
  • Now use the at commands to set baud rate using "at +uart=115200,0,0" e.g.
  • Use "at +uart?" to see what is the baud rate set on the device.

Connect Bluetooth device to Rx and Tx of Arduino.

Arduino <-> HC-05 ======= ======= 5V Vcc GND GND Rx Tx Tx Rx (Via Voltage divider)

Some of the articles talk about connecting 3.3V of Arduino to the Vcc of HC-05 and not using the voltage divider at all. However this combination fails as once increases the baud rate.

Check out more details about voltage divider here. https://electronics.stackexchange.com/questions/280500/why-do-you-have-to-use-a-voltage-divider-with-hc-05-bluetooth-module-arduino

What is the story of two COM devices for Bluetooth?

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