SD卡连续读写文件报错

发布于 2020-07-20 09:41:10 浏览：2111 订阅该版

硬件：STM32F103RET6, SD卡，485从设备
内核：4.0.2
工具: Rt-Thread Studio 1.1.2

项目上需要从485从设备读数据，然后写到csv文件里，每5-10秒写一次，每次写一行。csv文件是放在sd卡上的，sd卡挂载在"/"路径。

文件我每次打开、追加、关闭，这个操作没问题。但是重复700次左右，DFS就报错了，错误如下`（DFS fd new is failed! Could not found an empty fd entry.)`：
![Snipaste_2020-07-20_09-37-20.png](/uploads/20200720/397463370258640e10370a72859f070d.png)

这部分操作的代码：

```c
static void im3318_main(void* parameter)
{
    int regs = {0};
    struct tm *t;
    time_t now=0;
    char file_name[20];
    char write_buf[256] = {0};
    char print_buf[256] = {0};
    char current_time[64];

while(1){

// 读寄存器
        regs = modbus_read_registers(ctx, PHASE_A_REG_START, REG_LEN*3, readBuffer_BCD);

// 判断读寄存器是否正确
        if (regs == REG_LEN*3) {

// 转换BCD码
            bcd_dec_arrary(readBuffer_BCD, readBuffer, REG_LEN*3);

// 存入变量列表
            im3318_write_buffer(readBuffer);

// 获取时间
            now=time(RT_NULL);
            t = rt_malloc(sizeof(struct tm));
            t = localtime(&now);

// 生成文件名（按月份）
            sprintf(file_name, "%d-%02d-%02d.csv", t->tm_year+1900, t->tm_mon+1, t->tm_mday);

// 生成当前时间
            sprintf(current_time, "%d-%02d-%02d,%02d:%02d:%02d", \
                    t->tm_year+1900, t->tm_mon+1, t->tm_mday, t->tm_hour, t->tm_min, t->tm_sec);

// 有SD卡情况下才写文件
            device = rt_device_find("sd0");

if (device != RT_NULL) {

fd = open(file_name, O_APPEND | O_CREAT | O_WRONLY);

if (fd>0) {

write_cnt++;
                    rt_kprintf("fd=%d, write cnt = %d\n", fd, write_cnt);

// for Writing to file
                    sprintf(write_buf, "%s,%lf,%lf,%lf,%lf,%lf,%lf,%lf,%lf,%lf,%lf,%lf,%lf\n", \
                            current_time, Pa, Qa, Ua, Ia, Pb, Qb, Ub, Ib, Pc, Qc, Uc, Ic);
                    write(fd, write_buf, strlen(write_buf));

// for Printing
                    if (debug_on) {
                        sprintf(print_buf, "%s:\n"
                                "Pa=%lf, Qa=%lf, Ua=%lf, Ia=%lf\n"
                                "Pb=%lf, Qb=%lf, Ub=%lf, Ib=%lf\n"
                                "Pc=%lf, Qc=%lf, Uc=%lf, Ic=%lf\n", \
                                current_time, Pa, Qa, Ua, Ia, Pb, Qb, Ub, Ib, Pc, Qc, Uc, Ic);
                        rt_kprintf("%s", print_buf);
                    }

}else{
                    failed_cnt++;
                    // 如果失败3次以上，重启
                    if (failed_cnt > 3) {
                        rt_hw_cpu_reset();
                    }
                    rt_kprintf("Write File Error\n");
                }

close(fd);
            }

}else{
            failed_cnt++;
            // 如果失败3次以上，重启
            if (failed_cnt > 3) {
                rt_hw_cpu_reset();
            }
            rt_kprintf("Read Register Error\n");
        }

rt_thread_mdelay(acq_time*1000);
    }

}
```