前言

本章测试sd卡的读写速度，编写代码实现书籍信息录入。

sd卡读写测试

通过dmesg查看kernel log

不支持F2FS

支持 fat32

【命令】fdisk -l

读写测试

写入：dd if=/dev/zero of=/run/media/mmcblk1p1/test bs=1M count=500
conv=fsync

读取：dd if=/run/media/mmcblk1p1/test of=/dev/null bs=1M

读取txt文档

书籍录入

串口屏内输入书籍信息，存储进sd卡的txt文件中，在设备上读取文件。

sd卡路径：/run/media/mmcblk1p1

【命令】cat /run/media/mmcblk1p1/b.txt

代码

/******************************************************************************************
Module Name: 		main
Description: 		save book msg to txt
Formal Parameter:
Date: 				2022/12/11
Author: 			youkai
*****************************************************************************************/

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <stdbool.h>
#include "stdint.h"
#include "stddef.h"

#define SIZE		100
#define SIZE_R		100

#define FILE_NAME	"/run/media/mmcblk1p1/b.txt"
#define C_ALOGE_PRINTF printf

int L_end=0;
int Current_cursor = 0;
uint8_t book_name[20];
uint8_t book_num[10];
uint8_t book_addr[20];
uint8_t book_msg[100];


int f_write(uint8_t* buff, FILE * file )
{
	if( EOF == fputs( buff, file ))
	{
		C_ALOGE_PRINTF("can not fput one line.\n");
		C_ALOGE_PRINTF("fputs wrong \n");
		return 0;
	}
	else
	{
		// C_ALOGE_PRINTF("fputs ok \n");
		if(buff[0]!='\n')
			C_ALOGE_PRINTF("line: [%s]\n",buff);
		return 1;
	}
	C_ALOGE_PRINTF("%s error\n",__func__);
	return -1;

}

int f_read(uint8_t* buff, int len, FILE * file )
{
	if( NULL == fgets( buff, SIZE, file ))
	{
		C_ALOGE_PRINTF("can not get one line.\n");
		C_ALOGE_PRINTF(" fgets wrong ");
		return 0;
	}
	else
	{
		// C_ALOGE_PRINTF("fgets ok \n");
		C_ALOGE_PRINTF("line: [%s]\n",buff);
		return 1;
	}
	C_ALOGE_PRINTF("%s error\n",__func__);
	return -1;
}

int l_read(uint8_t* buff, FILE * file)
{
	fscanf(file,"%[^\n]", buff);
	C_ALOGE_PRINTF("%s: [%s]\n\n",__func__,buff);

	return 0;
}

int f_endline(FILE * file )
{
	//文件偏移量设置为文件的大小加上偏移量字节
	L_end=fseek(file, 0, SEEK_END);
	if(L_end == 0)
	{
		C_ALOGE_PRINTF("%s error\n",__func__);
		return -1;
	}
	else
		C_ALOGE_PRINTF("file size is %d",L_end);
	return 0;

}

//
int bookmsg(uint8_t *name, uint8_t *num, uint8_t *addr)
{
	memset( book_msg, '\0', sizeof(book_msg));

	strcpy(book_msg,name);
	strcat(book_msg," , ");
	strcat(book_msg,num);
	strcat(book_msg," , ");
	strcat(book_msg,addr);
	// strcat(book_msg,"\n");

	C_ALOGE_PRINTF("name=[%s], num=[%s], addr=[%s], msg=[%s]\n",name,num,addr,book_msg);
	return 0;
}

int save_bookmsg(FILE * file)
{
	int size_msg=strlen(book_msg);
	C_ALOGE_PRINTF("bookmsg size is [%d]\n",size_msg);

	if( 0 != fseek( file , Current_cursor , SEEK_SET ))
	{
		perror(" fseek wrong : \n");
		C_ALOGE_PRINTF(" fseek wrong \n");
	}
	f_write(book_msg, file);
	f_write("\n", file);

	C_ALOGE_PRINTF("\n");

	return 0;

}

int main()
{
	FILE *f_mem = NULL;							//file point

	int i = 0;									//temp
	static int line = 0;						//which line
	// static int Current_cursor = 0;				//save current cursor

	uint8_t buff[SIZE] = {0};						//save one line char root

	/*1. open file read&write*/
	f_mem = fopen( FILE_NAME , "rt+");		//open file read&write
	if(NULL == f_mem)						//judge whether the file cannot open
	{
		perror(" fopen wrong ");
		C_ALOGE_PRINTF(" fopen wrong ");	//logcat
	}
	else
		C_ALOGE_PRINTF("Success to open file!\n\n");

	//2. cursor set to file first line
	/*file pointer points to the start of one line*/
	// if( 0 != fseek( f_mem , Current_cursor , SEEK_SET ))
	// {
	// 	perror(" fseek wrong : \n");
	// 	C_ALOGE_PRINTF(" fseek wrong \n");
	// }

	//2. read first line, 
	memset(buff, '\0', SIZE);	//clear buff
	bookmsg("书名","ISBN号","地址");
	save_bookmsg(f_mem);


	// l_read(buff,f_mem);
	// f_read(buff, SIZE, f_mem);

	//3. save cursor
	Current_cursor = ftell( f_mem );	//save the cursor of next line
	C_ALOGE_PRINTF("current cursor=%d\n",Current_cursor);

	// f_endline(f_mem);

	if( 0 != fseek( f_mem , 0 , SEEK_SET ))
	{
		perror(" fseek wrong : \n");
		C_ALOGE_PRINTF(" fseek wrong \n");
	}

	l_read(buff,f_mem);

	// strcpy(buff,"xxx");

	bookmsg("这里是中国","67890","北5柜");
	save_bookmsg(f_mem);

	/*close file*/
	if((fclose(f_mem)) == 0)					//关闭文件
	{
		//printf("Success to close demo.dat!\n");
		C_ALOGE_PRINTF("Success to close file!\n");
	}
	else
		C_ALOGE_PRINTF("!!! fclose wrong \n");		//logcat
	f_mem = NULL;

	return 0;
}

这是里只是文件存储的代码，串口传输的放在csdn上了。

小结

sd卡读写功能正常，可以实现串口屏录入书籍信息存储到sd卡文件中这一功能。