API - 0 (API mode is off) means all UART input and output is raw data and packets are delineated using the RO and RB parameters.
API - 1 (API mode is on) means all UART input and output data is packetized in the API format, without escape sequences.
API - 2 means API mode is on with escaped sequences inserted to allow for control characters (XON, XOFF, escape, and the 0x7e delimiter to be passed as data).