[ts-7000] Problem write on rs-485 TS7800

["rodriguezromain62" <>]

Hello all, I have a problem with the function write(fd,data,sizeof(data));

I use a rs-485 to get value of a PT100 temperature sensor.
I put a 0 to bit 15 on register 0xE800000C to get rs-485 ON
the PT100 needs a command to return temperature, so I need to send some char, 
like "TAI".

I try this : fprintf(stderr,"%c",write(fd, 'T', 1));
             fprintf(stderr,"%c",write(fd, 'A', 1));
             fprintf(stderr,"%c",write(fd, 'I', 1));

But it doesnt work, I dont have a "TAI" print to my screen, I have "???"
I guess its not the good way.

init :

if ((fd = open(devname, O_NOCTTY | O_RDWR)) == -1) {
                perror("Can't open serial line");
                exit(1);
        }
        FD_ZERO(&readfd);
        FD_ZERO(&exceptfd);
        signal(SIGINT, catch_int);
        tcgetattr(fd, &oldsetting);
        memcpy(&newsetting, &oldsetting, sizeof(newsetting));
        cfmakeraw(&newsetting);
                cfsetspeed(&newsetting, speed);
        }
        tcsetattr(fd, TCSANOW, &newsetting);
        
        numfds = (fd > STDIN_FILENO? fd : STDIN_FILENO) + 1;
        while (1) {
                timeout.tv_sec = 1;
                timeout.tv_usec = 0;
                //FD_SET(STDIN_FILENO, &readfd);
                FD_SET(fd, &readfd);
                //FD_SET(STDIN_FILENO, &exceptfd);
                FD_SET(fd, &exceptfd);
                select(numfds, &readfd, NULL, &exceptfd, &timeout);



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