C library

src/mscb.cxx exposes a C-compatible interface through include/mscb.h. Applications include the header, initialize a connection, operate on node addresses and close the descriptor.

#include "mscb.h"

int main(void)
{
    char device[256] = "192.0.2.40";
    int fd = mscb_init(device, sizeof(device), "", 0);
    if (fd < 0)
        return 1;

    if (mscb_ping(fd, 1, 0, 1) == MSCB_SUCCESS) {
        float value = 0;
        int size = sizeof(value);
        if (mscb_read(fd, 1, 0, &value, &size) == MSCB_SUCCESS) {
            /* use value; inspect variable metadata before assuming a type */
        }
    }

    mscb_exit(fd);
    return 0;
}

Important conventions

• A non-negative descriptor returned by mscb_init() identifies a connection.
• Most operations return an MSCB_* status; initialization may return a negative EMSCB_* error.
• Read MSCB_INFO_VAR before interpreting raw value bytes. Width and flags determine representation.
• size in read APIs is both input capacity and output byte count.
• The library serializes access with a per-device lock. Do not retain internal descriptor-table pointers.
• mscb_flash() persists node settings and is slower than an ordinary write.

The complete function list is in the C API reference, with structures and result codes under types and status. C++ applications can instead use the higher-level MSCB++ API.

Ethernet behavior

For an Ethernet descriptor, API operations become one or more version-5 UDP exchanges with the submaster. Address cycles and command bytes are kept separate so the submaster can create the RS-485 ninth bit. See Ethernet transport.