Thread: problem C-Program (Cache?, Storage?, ...)

Hey guys,
I run a C-Program on a raspberry pi (Linux) and the Code funtion, but there is maybe a cache Problem. It is used to get data from a Sensor.

If I run the program and ask for example the temperature, the sensor gives me the temperature. But if I asked after this the Humidtiy for example it don't function anymore.
When I restart the program then I can ask again for a value.

So maybe it is a chache problem with sending the commands?

Maybe you can help me

Code:

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <fcntl.h>
#include <termios.h>
#include <signal.h>
#include <errno.h>


static sig_atomic_t end = 0;


static void sighandler(int signo)
{
    end = 1;
}


int main(int argc, char** argv)
{
    struct termios tio;
    int tty_fd;
    struct sigaction sa;


    memset(&sa, 0, sizeof(struct sigaction));
    sa.sa_handler = sighandler;
    sigaction(SIGINT, &sa, NULL);
    sigaction(SIGQUIT, &sa, NULL);
    sigaction(SIGTERM, &sa, NULL);


    printf("RS232\n\n");


    memset(&tio, 0, sizeof(tio));
    tio.c_iflag = 0;
    tio.c_oflag = 0;
    tio.c_cflag = B9600 | CS8 | PARODD | CREAD | CLOCAL;
    tio.c_lflag = 0;
    tio.c_cc[VMIN] = 1;
    tio.c_cc[VTIME] = 5;


    printf("Open device\n");
    tty_fd = open("/dev/ttyAMA0",O_RDWR | O_NONBLOCK);
    if (-1 == tty_fd)
    {
        printf ("unableto open device, error '%s' (%d)\n",
        strerror(errno), errno);
        return EXIT_FAILURE;
    }


    cfsetospeed(&tio, B9600);
    cfsetispeed(&tio, B9600);
    tcsetattr(tty_fd, TCSANOW, &tio);


    //_____________________________________________________________________________________


    int choose = 0;


    do
    {
        printf("1. Temperature\n");
        printf("2. Humidity\n");
        printf("3. CO2\n");
        printf("4. Exit\n");
        scanf("%d", &choose);
        printf("\n");


        switch (choose)
        {
            case 1: // Temperature
            {
                char command1[] = "T\r\n";
                float temp;
                char *p1;
                unsigned char buftemp[8];
                char buftemp2[5];


                write(tty_fd, &command1, 5);


                while (!(read(tty_fd, &buftemp, 8) && buftemp[0]>0))
                {


                }
                memmove (buftemp2, buftemp + 3, 5);
                temp = strtof(buftemp2, &p1);
                temp = temp - 1000;
                temp = temp / 10;


                printf("Temperature: %.2f C\n", temp);


                break;
            }


            case 2: // Humidity
            {
                char command2[] = "H\r\n";
                float humi;
                char *p2;
                unsigned char bufhumi[8];
                char bufhumi2[5];


                write(tty_fd, &command2, 5);


                while (!(read(tty_fd, &bufhumi, 8) && bufhumi[0]>0))
                {


                }
                memmove (bufhumi2, bufhumi + 3, 5);
                humi = strtof(bufhumi2, &p2);
                humi = humi / 10;


                printf("Humidity: %.2f %\n", humi);


                break;
            }


            case 3: // Carbondioxide
            {
                char command3[] = "Z\r\n";
                float carb;
                char *p3;
                unsigned char bufcarb[8];
                char bufcarb2[5];


                write(tty_fd, &command3, 5);


                while (!(read(tty_fd, &bufcarb, 8) && bufcarb[0]>0))
                {


                }
                memmove (bufcarb2, bufcarb + 3, 5);
                carb = strtof(bufcarb2, &p3);


                printf("Carbondioxide: %.2f ppm\n", carb);


                carb = carb / 10000;


                printf("Carbondioxide: %.2f %\n", carb);


                break;
            }
        }
    }
    while (choose !=4);


    close(tty_fd);


    return 0;
}