接上上篇目的demo

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#include <stdio.h>   #include <fcntl.h>   #include <stdlib.h>   #include <string.h>   #include <linux/i2c-dev.h>   #include <errno.h>     int main(int argc, char *argv[])  {      int num, err, i, j;      int fd, addr;      char *buff;            printf("please input as:");      printf("./wat24 [data]\n");      fflush(stdout);            if(argc < 3){          printf("arg error\n");          return -1;        }      num = argc - 1;        buff = malloc(num*sizeof(char));      if(buff < 0){          printf("alloc failed\n");          return -1;      }        buff[0] = atoi(argv[1]);            printf("write data:\n");      for(i = 1; i < num; i++){          buff[i] = atoi(argv[i + 1]);          printf("%d\n",buff[i]);      }      printf("from word addr:%d\n",buff[0]);        fd = open("/dev/i2c-0",O_RDWR);      if(fd < 0){          printf("device open failed\n");          return -1;        }            err = ioctl(fd, I2C_SLAVE_FORCE, 0x50);      if(err < 0){          printf("ioctl failed:%d\n",err);          return -1;      }            write(fd, buff, num);            close(fd);      return 0;  }

#include <stdio.h>  #include <linux/types.h>  #include <stdlib.h>  #include <fcntl.h>  #include <unistd.h>  #include <sys/types.h>  #include <sys/ioctl.h>  #include <errno.h>  #include <assert.h>  #include <string.h>  #include <linux/i2c.h>  #include <linux/i2c-dev.h>    int main(int argc, char **argv)  {      struct i2c_rdwr_ioctl_data e2prom_data;      unsigned int fd;      unsigned int slave_address, reg_address,value;       //slave_address为eeprom的地址，reg_address为eeprom中存储单元的地址，范围0x0--0xFFFFFFFF,value为你要写进eeprom的值      int ret;            if (argc < 5){          printf("Usage:\n%s /dev/i2c/x start_addr reg_addr value\n",argv[0]);          return 0;      }            fd = open(argv[1], O_RDWR);            if (!fd){          printf("Error on opening the device file\n");          return 0;      }        sscanf(argv[2], "%x", &slave_address);      sscanf(argv[3], "%x", &reg_address);      sscanf(argv[4], "%x", &value);            e2prom_data.nmsgs = 2;//因为都时序要两次，所以设为2      e2prom_data.msgs = (struct i2c_msg *)malloc(e2prom_data.nmsgs * sizeof(struct i2c_msg));      if (!e2prom_data.msgs){          printf("Memory alloc error\n");          close(fd);          return 0;      }            ioctl(fd, I2C_TIMEOUT, 2);//设置超时时间      ioctl(fd, I2C_RETRIES, 1);//设置重发次数        /* write data to e2prom*/      e2prom_data.nmsgs = 1;      e2prom_data.msgs[0].len = 2;//信息长度为2，看写时序，eeprom的地址不算的，因为付给了addr，而len是指buf中的值的个数      e2prom_data.msgs[0].addr = slave_address;      e2prom_data.msgs[0].flags = 0;//写命令      e2prom_data.msgs[0].buf = (unsigned char*)malloc(2);      e2prom_data.msgs[0].buf[0] = reg_address;//信息值1 eeprom中存储单元的地址，即你要往哪写      e2prom_data.msgs[0].buf[1] = value;//信息值2,即你要写什么            ret = ioctl (fd, I2C_RDWR, (unsigned long)&e2prom_data);//好了 ，写进去吧      if (ret < 0){          printf ("ioctl write error\n");      }        printf("you have write %02x into e2prom at %02x address\n",value,reg_address);            sleep(1);      /*read data from e2prom*/      e2prom_data.nmsgs = 2;//读时序要两次过程，要发两次I2C消息      e2prom_data.msgs[0].len = 1;//信息长度为1，第一次只写要读的eeprom中存储单元的地址      e2prom_data.msgs[0].addr = slave_address;      e2prom_data.msgs[0].flags = 0;//写命令，看读时序理解      e2prom_data.msgs[0].buf[0] = reg_address;//信息值                e2prom_data.msgs[1].len = 1;      e2prom_data.msgs[1].addr = slave_address;      e2prom_data.msgs[1].flags = I2C_M_RD;//读命令      e2prom_data.msgs[1].buf = (unsigned char*)malloc(1);      e2prom_data.msgs[1].buf[0] = 0;//先清空要读的缓冲区      ret = ioctl (fd, I2C_RDWR, (unsigned long)&e2prom_data);//好了，读吧      if (ret < 0){          printf ("ioctl read error\n");      }            printf("read %02x from e2prom address %02x\n",e2prom_data.msgs[1].buf[0], reg_address);            close(fd);      return 0;     }

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