Combines Bluetooth 3.0 Audio Module with Class-D Amplifier and 4.2V Li-ion Battery Charger for wearable/portable audio projects. Rev 3 now includes USB to UART bridge and uses the WT32i internal battery charger. WT32i DATASHEET REQUIREMENT: "The chip antenna of WT32i requires only a small metal clearance area directly under the antenna. The antenna operation is dependent on the GND planes on both sides of the antenna. Minimum 15mm of GND plane must be placed on both sides of the module and the GND plane of the motherboard must reach under the edges of the module." 15MM on each side + 16MM wide WT32i module = 46MM wide PCB MINIMUM. Don't forget to remove the copper fill beneath the antenna for every layer! Since I'm using this for a sleeping mask/headphone I can get away with making the ground plane and PCB slightly smaller for a shorter range but EMI will be worse. You should use GND via's to help reduce EMI creating a faraday cage with vias around the permiter of the PCB as shown in the WT32i Reference Design PDF. This will help prevent some EMI leakage and improve audio quality from internal PCB interference. What is so great about this module? In theory, you should be able to customize it by directly plugging it into a PC with a USB data cable and running the iWrap software. If you use the APT-X version you should be able to connect to 2 devices simultaneously. How much you want to customize it for your audio uses (sleeping mask, headphones, portable boom box) while using iWrap is up to you! This should empower users to customize their bluetooth devices for their own specific needs. A sleeping mask will have lower audio alerts or none compared to a headphone or small portable speaker box. When it comes to getting a good nights sleep and not being jolted out of bed by a low battery warning at 100% volume you'll realize that being able to customize things like alert volumes, tones, battery size, charge output, does matter, a lot. To recharge the module while running on a 4.2V Li-ion battery simply use a USB charging cable instead of a data cable. I designed this module specifically to work with a 2500mAh Li-ion battery. Silicon Labs CP2102N USB to UART Module. Program with Simplicity Studio. Silicon Labs WT32I-A-AI61-APTX Bluetooth Module. Customize the WT32i via CP210N UART bridge with BlueGiga iWrap terminal software. SPI headers are for firmware updates only, unlikely you will ever need to use the SPI headers. UNTESTED/UNVERIFIED MODULE