We wish to create a low-cost consumer audio playback device (PCB only) using a BT201 https://ibb.co/qDY7t6y audio board. This board is capable of storing and playing back MP3 files from local storage on a TF card (16 GB) and includes audio output as well as a built-in amplifier and Bluetooth 5.0 (BLE) and the ability to connect a 5V battery as well as expand onto the board via serial interface. Use dual 1000 mAh Lithium-Ion rechargeable batteries with a USB charging to power the board for 20 hours of continuous playback. Playback [non-streaming] will be through a single 3.5” 4omh/3W speaker. In addition we will add a separate powered relay to power a 2” computer CPU fan. You will then write a simple PC application to control audio playback (next/prev track, vol +/-, power and fan on/off) over BLE on a Windows PC using a BT USB adapter. The BT201 has functional firmware on it from the manufacture that can modified as required. Additional features should include a bi-color LED for status indication (solid orange = on, blinking orange = low battery, solid blue = BT connected, flashing blue = BT pairing, no light = off) + optional battery capacity status output to PC. The deliverable PCB once confirmed should be production ready for manufacturing. The aim of this project is to significantly reduce engineering and development by using off the shelf hardware to quickly produce a product for low-volume sales. Milestone 1 is to research and submit a BOM of components and milestone 2 is for a working test circuit to analyze the device and milestone 3 is for a completed functional prototype ready for manufacturing. We would like the completed board to cost $15-25 USD approximately e/a. Preferred deliverables are ASAP (rapid-development). Please quote this project competitively to engineer a functional prototype.