@spookyrufus It depends whthter you have a 736x or 738x model. When you operate the device from 3.3V, you shoul dbe able to connect the Serial out from the sensor directly to the Uart RX. If it is a 736x model, you'll need a Inverter, like you can do with a 2N7000: gate -> Sensor, Source -> GND, Drain -> RX, 10k Pullup-Resistor between RX and Vcc. You may also use an inverter chip, like 74hc04 ....