The serial data stream that the Renix ECU produces is a 30-byte long frame of data and can be read by any UART interface (arduino, pycom, raspberrypi, etc). To identify the starting sequence, there is a 0xFF marker immediately followed by a 0x00 start.

Simple enough, except when a measurement is 0x00 or 0xFF. In the former case, a value of zero is only valid if not preceded by a 0xFF marker. And in the latter case, if the measurement value is the maximum value of a byte (ie 0xFF), it must be sent twice.