Introduction: DIY Bluetooth Adapter.

About: I am an electrical repair tech by day and an engineer by night, after work or free time.

After making my Bluetooth speaker from scratch I was left with a lot of parts and a few XS3868 Bluetooth modules so I decided to take those and make a simple Bluetooth adapter to use as a bridge between my phone and whatever audio amp that only has a corded input!

Sure, you can go out and buy a Bluetooth adapter but where's the fun in that? Lets get started!

The components used for this project are included in the BOM txt file that's attached. Aside from what's in that file you will need a lithium ion battery, on/off switch, 3.5mm jack and an enclosure of sorts.

If you wish to reproduce this project please do so at your own risk. This involves soldering and the handling of lithium ion batteries.


Step 1: Watch the Video!

I covered the entire build in this video feel free to check it out and leave some comments if you'd like.

Step 2: The Schematic and Board Explained

The schematic behind this project is relatively simple. It can be broken down into two parts, the battery charging circuit and the Bluetooth module portion. Since it doesn't require a lot of parts this allows for a small board.

I wanted this adapter to have the ability to charge a battery so it can provide power to the Bluetooth module. I used the TP4056 IC for this, once the battery is charged its stored energy can be passed to the Bluetooth module portion by the use of the "S" pads which act as solder pads for an external on/off switch. I used surface mount pads for every external connection to make the board as modular as possible to fit a wide variety of enclosures. The Bluetooth module can use switches to carry out commands such as skip, volume and pause. I included these pads in the schematic and board but didn't use them for my project but the option is there!

The pads labeled 5+ and and 5- are for mounting a 5 volt input to charge the battery, the B+ and B- are for the battery, and the AL, AR and AG are the audio output pads for the 3.5mm jack.

You can download the gerber files for this project here

This project is opensource so if you run into any issues with the design please feel free to reach out to me.

Step 3: Assembly.

I ordered my boards from JLCPCB and as always the quality and time can't be beat. I soldered every component and cleaned with isopropyl alcohol. This board was designed using 0603 components which isn't the best size for beginners to solder but with practice you'd be surprised how easy they become to solder.

Step 4: Housing the Board.

As mentioned earlier I designed this board to be modular as possible to accommodate housing options not only because I lack a 3d printer but because others do as well.

I found these project boxes on amazon and they turned out to be a near perfect fit. I mounted an on/off switch, micro usb port and 3.5mm jack to the box as well as made holes for the led viewings.

Step 5: Programming the Module.

The XS3868 can be programmed to change a variety of default settings. You don't have to program the device in order to use it but if you'd like to program the module you will need a ttl to usb device and the programming software. The software can be downloaded from this step.

On the Bluetooth board I included a RX, TX and TTL- pads for programming. In short, in order to program the module you will need to solder the ttl to usb device RX, TX and gnd wires to the correct pads on the board. After opening the software and supplying power to the board the "red not connected" will turn green to show that the device is connected and now you can edit the contents of the module.

I covered the programming portion in my video but if you'd like more information on this module I recommend checking out this instructable by author UtkarshVerma. They dedicated an entire instructable to this module and it's worth the read!

When connecting the ttl device to the board follow this

RX from ttl device connects to TX on the board

TX from ttl device connects to RX on the board

Gnd from ttl device connects to TTL- on the board.

Step 6: Charge and Use!

Now you can use this device to stream audio from your phone to a speaker system that has a 3.5mm aux cord for wireless enjoyment!

If you want to take this a step further you can utilize the button pads for more device functionality. Thanks for checking out my ible! Feel free to ask me questions in the comments below and follow for more :)