TF Card Read/Write Demo

1 Demo Introduction

This demo mainly demonstrates how to mount a TF card into the Linux filesystem, perform read/write operations on the TF card, and manage files.

2 Mount the TF Card

root@linaro-alip:/# fdisk -l
···
Disk /dev/mmcblk1: 29.72 GiB, 31914983424 bytes, 62333952 sectors
Units: sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disklabel type: gpt
Disk Identifier: 23000000-0000-4C4A-8000-699000005ABB

View the partition information of the TF card. mmcblk1p1 is a partition of the TF card device and can be mounted into the Linux system.

root@linaro-alip:/# lsblk
NAME         MAJ:MIN RM  SIZE RO TYPE MOUNTPOINTS
mmcblk1      179:0    0  7.4G  0 disk
└─mmcblk1p1  179:1    0  7.4G  0 part

Create a mount point and mount the device:

sudo mkdir /mnt/tfcard
sudo mount /dev/mmcblk1p1 /mnt/tfcard

View the mount result; it has been mounted successfully.

root@linaro-alip:/# df -h
………
/dev/mmcblk1p1  7.5G   16K  7.5G   1% /mnt/tfcard

3 Demo Procedure

After successfully mounting the TF card, follow the procedure below to perform read/write operations and file management on the TF card.

Open a terminal and copy the executable smdt_TF from the bin directory of this demo (05-开发资料\软件开发资料\linux_demo\smdt_TF_demo\bin) to the development board's filesystem (the source code can be found in the src directory).

#修改 Linux 内核日志的显示级别，内核的日志级别被设置为只显示紧急或更高级别的消息
echo 1 4 1 7 > /proc/sys/kernel/printk

In the terminal, run the following commands to switch to the directory containing the smdt_TF executable.

#切换到 smdt_TF 可执行程序所在目录
cd ‘可执行文件所在目录’

#查看 smdt_TF 是否在该目录下
ls

If the executable smdt_TF is in the current directory, modify the executable's permissions.

#修改文件权限
chmod 777 smdt_TF

#查询是否修改成功
ls -ld smdt_TF

After confirming that the file permissions have been successfully modified, run ./smdt_TF -h to view the program's help information.

root@linaro-alip:/# ./TF -h
Usage:
  -w "<text>" <file>  Write <text> to <file>
  -r <file>         Read and print the content of <file>
  -d <file>         Delete the specified <file>
  -ls              List all files and directories in the TF card
  -h                Show this help message

Perform a write operation on the TF card.

root@linaro-alip:/# ./TF -w "HELLO SMDT" test.txt
Data written to /mnt/tfcard/test.txt

View the files in the TF card. You can see that test.txt has been created.

root@linaro-alip:/# ./TF  -ls
Files and directories in /mnt/tfcard:
System Volume Information
test.txt

Read the written file; it matches the written information.

root@linaro-alip:/# ./TF -r test.txt
Read from file: HELLO SMDT

Delete the file. Check the mount directory and you can see that the file has been deleted.

root@linaro-alip:/# ./TF -d test.txt
File /mnt/tfcard/test.txt deleted successfully.
root@linaro-alip:/# ./TF -ls
Files and directories in /mnt/tfcard:
System Volume Information

Finally, unmount the device.

umount /mnt/TF_Card