Chapter 3. API Specifications

This is a highly simplified example of using a few of the Cogent C API functions, with no error checking etc. It leaves the actual work of read/writing the values from/to the buffer as an exercise for the reader.

#include ("dr_api.h");
#include ("dvn_api.h");

int main (int argc, char ** argv)
{
    char  dvn_data[1024];
    int   scanning=1;

    if (!DR_ApInitIPC (argv[0], "/dr/dvn"))
    {
        /* read the configuration of points */
        /* ..... */
    
        while (scanning)
        {
            DR_ApUpdateBuffers ();
    
            DR_ApReadBlock (0, DVN_BUF_INPUT, 0, 64*8, dvn_data, NULL);
            /*
             * read/write the data as required.
             * eg: if 'point' is an object in a linked list that
             *     models where the data is, then for each point:
             *   point.value = dvn_data[point.dvn_offset]&point.dvn_bit_mask;
             * ...
             *   dvn_data[point.dvn_offset] = modbus_data[point.mbs_offset];
             * etc.
             */
            DR_ApWriteBlock (0, DVN_BUF_OUTPUT, 0, 64*8, dvn_data, NULL);
        }
        DR_ApCloseIPC();
    }
}