Detailed Description

HART / HART-IP process-instrument protocol codec (DETWS_ENABLE_HART).

HART (Highway Addressable Remote Transducer, FieldComm) is the field-instrument protocol that rides the 4-20 mA current loop as an FSK signal, and - as HART-IP - travels over UDP/TCP 5094 as the gateway-friendly, front-end-free path. This is the wire codec for both:

The HART command frame: [delimiter][address...][command][byte-count][data...][checksum], where the checksum is the longitudinal XOR parity of every byte from the delimiter through the last data byte (the preamble of 0xFF sync bytes is transport, not checksummed). Short (1-byte polling) and long (5-byte unique-ID) addressing are both handled by passing the address bytes.
The HART-IP message header (8 octets): version, message type, message id, status, a 2-byte sequence number, and the 2-byte total message length - wraps a HART PDU for UDP/TCP transport.

Pure, zero heap, no stdlib, host-testable. The FSK physical layer (a HART modem IC over UART) is the hardware-gated path; HART-IP needs no front end.

Definition in file hart.h.