What does the Biasing feature of the Connective Peripherals converter do?
Some models of converter have jumpers to enable bias resistors. These are used to pull the Data+ line up to 5V and to pull the Data - line down to 0V to ensure that the lines always go to a known state when no device on the serial bus is driving them. Receiving additional unexpected 0x00 bytes at the start or end of a message is one symptom which can indicate that biasing is needed. Biasing should not be enabled on more than one device on the RS485 bus as this can cause overloading of the line drivers when devices try to drive data onto the bus, and so check that other nodes do not have bias resistors before enabling them on your Connective Peripherals converter.