Cisco Bluetooth Serial adapter. Cutout enough space in the end of a 2P 18650 USB battery bank for the RJ45, and wire the power pins to pins 1 (+) & 4 (-) of the USB-A connector. All capacitors are .1uF 1206 SMD, resistors in the big group are for level shifting down to the 3.3V logic. All resistors are 470 ohm 1206 SMD, though exact values aren’t critical. Only 1 LED should be populated, with the anode (+) towards the center of the board.