问MAX31865 SPI通信失败

EN

#include <stdint.h>
#include <unistd.h>
#include <stdio.h>
#include <stdlib.h>
#include <getopt.h>
#include <fcntl.h>
#include <sys/ioctl.h>
#include <linux/types.h>
#include <linux/spi/spidev.h>


static void pabort(const char *s)
{
    perror(s);
    abort();
}

static const char *device = "/dev/spidev0.0";
static uint8_t mode = 3;
static uint8_t bits = 8;
static uint32_t speed = 1000000;
static uint16_t delay;

#define ARRAY_SIZE(a) (sizeof(a) / sizeof((a)[0]))


static void transfer(int fd)
{
    int ret;
    uint8_t tx[] ={0x80};

    uint8_t rx[1];
    struct spi_ioc_transfer tr = {
        .tx_buf = (unsigned long)tx,
        .rx_buf = (unsigned long)rx,
        .len = ARRAY_SIZE(tx),
        .delay_usecs = delay,
        .speed_hz = 0,
        .bits_per_word = 0,
    };

    ret = ioctl(fd, SPI_IOC_MESSAGE(1), &tr); //->> this ioctl function makes problems
    if (ret == 1)
         pabort("can't send spi message");

 }

int main(int argc, char *argv[])
{
    int ret = 0;
    int fd;

    fd = open(device, O_RDWR);
    if (fd < 0)
        pabort("can't open device");

    ret = ioctl(fd, SPI_IOC_WR_MODE, &mode);
    if (ret == -1)
        pabort("can't set spi mode");

    ret = ioctl(fd, SPI_IOC_RD_MODE, &mode);
    if (ret == -1)
        pabort("can't get spi mode");

    ret = ioctl(fd, SPI_IOC_WR_BITS_PER_WORD, &bits);
    if (ret == -1)
    pabort("can't set bits per word");

    ret = ioctl(fd, SPI_IOC_RD_BITS_PER_WORD, &bits);
    if (ret == -1)
        pabort("can't get bits per word");
    printf("%d",bits);

    ret = ioctl(fd, SPI_IOC_WR_MAX_SPEED_HZ, &speed);
    if (ret == -1)
        pabort("can't set max speed hz");

    ret = ioctl(fd, SPI_IOC_RD_MAX_SPEED_HZ, &speed);
    if (ret == -1)
        pabort("can't get max speed hz");

    printf("spi mode: %d\n", mode);
    printf("bits per word: %d\n", bits);  //---> This printf works fine

    transfer(fd);   
    printf("max speed: %d Hz\n", speed);  //--> This printf doesn't work

    close(fd);
}