Disassembling a Bluetooth speaker

As you may have noticed from my previous post, I am a fan of disassembling devices with the purpose of learning.

I got this nice Bluetooth speaker as a present from Redhat during a conference in Japan. It works by pairing your phone with the Bluetooth speaker to play music. The speaker provides three push buttons (volume down, play, volume up), a USB interface to charge the battery, a power on switch and a microphone.

The speaker's body is made of ABS plastic and covered by a rubbery silicone wrapper with a nice matte finish. The wrapper has a suction cup to stick the speaker to a surface. Let's look inside.

The body is held together with screws. The speaker and the microphone are glued to the top part. The printed board has pads for an extra microphone and LEDs. I suppose they left them there to customize the final product depending on the price. Finally, the lithium battery is glued to the bottom part.

The speaker is connected to the chip at the lower side of the board, an LTK8002D audio amplifier made by LTKCHIP TECHNOLOGY (ShenZhen). The brains of the Bluetooth speaker are implemented using the AC1533D83234, an SoC (System on chip) made by ZhuHai JieLi Technology (Zhuhai City). From what I could see by inspecting datasheets of similar chips, it (probably) contains a 32bit RISC CPU, GPIO pins, PWM, ADC, DAC and Bluetooth capabilities.

Conclusions: the way the Bluetooth speaker works is quite easy to understand. First, the SoC gets its power from the battery through a voltage rectifier (on the top side). The SoC also uses an external oscillator circuit to generate its own clock signals. The 3 buttons (and LEDs) are connected to the GPIO pins. When the switch is on and we press the play button, the SoC will receive audio data from our phone through the Bluetooth antenna which is printed onboard. Then, the SoC will convert these audio data into an analog signal, adjusting it to the current volume level. Finally, the SoC will forward the signal to the speaker through an audio amplifier. The most interesting part from disassembling this device has been finding and reading the website of ZhuHai JieLi Technology (thanks to Google translate!). I didn't even know this company existed. I wonder how many more companies and chips from China are left for me to discover.