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HC-06 Bluetooth Module

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Posted · HC-06 Bluetooth Module

Hey, has anyone experience connecting a HC-06 module to their UM1, it should be connected to a serial port and the only free port I could find is "Serial 3". This serial port is powered and I do get the Module to pair with my PC. But I do not get any communication going.

I think the UM1 is just not listening to the port, but the other two are occupied by the Ulticontroller.

Does anyone know how to connect this Serial bluetooth module. And should I use resistors as explained on some other forum.

Any help is appreciated.


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    Posted · HC-06 Bluetooth Module

    I managed to get it working!

    Connect the bluetooth module to the third serial port, this port only has 4 pins, located next to the connectors for the ulticontroller. I have measured the pins to be sure what is Vvc and Ground.

    Then get a new set of Marlin files and change the following settings in "Configuration.h" :


    #define SERIAL_PORT 3 // this is normally set to 0
    #define BTENABLED // enable this

    I have been able to communicate at baudrates of 9600 and up to 115200.

    Reception of the HC-06 Module is pretty poor, my UM sits about 8m from my PC and the signal is almost at its lowest, next step is improve this a bit.

    BTW these modules cost about $4 from ebay


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    Posted · HC-06 Bluetooth Module

    Great work, but what are your plans with it? Replacement of the USB cable or do you think about sending files to the UM ans store it at the SD?

    Maybe you could also post a picture of the PCB and the pin location.

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    Posted · HC-06 Bluetooth Module

    Well, as my UM sits on the other site of the room I got tired of picking it up to get it close enough to my PC for the USB cable. Mostly for firmware update or sometimes when I needed to fiddle with it.

    First of all the firmware, I have not been able to load it wireless. The Marlin firmware states that although the communication port is changed to "Serial 3", the bootloader will still listen to "Serial 0".

    I was hoping it would be listening to both the ports, but for now it doesn't work.

    I used the following connectios pins:

    UM PCB Serial3

    This is not my board but it looks similar, only thing is that on my board the silk contains the text "serial 3" next to the pins

    Btw, I had to cross connect the Tx and Rx as the order is different on the HC-06


    I also tried to print through the bluetooth connection, see the bots.

    UM Bots SD-Card vs Bluetooth

    Two Robots printed with the exact same settings, the left one printed using the SD-Card, it looks ok. The right bot is printed using the Bleutooth connection, not that nice (it even looks a bit sad :-P ).

    The Bluetooth print also took longer to print, and it was stuttering on the outer shell lines.

    The infill was (strangly) printed fluently?!?

    Q: Would it be possible to transfer the gcode to the SD-Card and then command to start the print wireless?


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    Posted · HC-06 Bluetooth Module

    The bootloader is usually fixed to a certain serial port. Sad, but it's the usual case...

    The reason why the infill was fine, but the shell wasn't, is that the infill is made out of long, straight lines. The shell however is made out of many small line segments.

    Every line is one gcode command that needs to be streamed. Short lines = many commands per second. Long lines = few commands per second.

    So I suppose it got buffer underruns, which resulted in lags (printer having to wait for the next command to be transmitted).


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    Posted · HC-06 Bluetooth Module

    Q: Would it be possible to transfer the gcode to the SD-Card and then command to start the print wireless?


    If someone writes the code, then yes, shouldn't be a problem. The firmware just needs to copy the input from the bluetooth module to the SD card.

    You'd probably have to do that at a very low baudrate, but technically it should work.

    Pair this with automatic pre-heating through the transmitted files (conventiently at the beginning of the file..) and you don't even lose much time.

    I suppose this goes on my wishlist for my own printer electronics ;)

    BT modules are pretty cheap to integrate, they basically throw them at you... :D


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    Posted · HC-06 Bluetooth Module

    Yeah you must be right about the buffer underruns, think its because of the bad bluetooth connection.

    I started this because I saw this video (

    ). This guy managed to get it to printing properly. Must have a better connection with only a few meters between his PC and UM.

    I have already extended the cable to position the HC-06 a bit better, but there is still room to improve.

    Also installed a android app, can be found here (https://play.google.com/store/apps/details?id=de.dietzm.gcodesimulator&hl=en) works pretty easy and could help me for the moment.


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