UART single-wire half-duplex level conversion
You can use the MAX3182 IC. It can take anything between +/-25V and convert it to either 3V3 or 5V. Check out the datasheet and decide which one suits you best. Looking at the waveform, it looks idle high, which is the case for TTL-UART, so you should use a non-inverting configuration (i.e. MAX3182 or MAX3183). Among the two, one supports a "not output enable" input and the other - a "not invalid" output, so decide for yourself if you need either of the two functions.