Beginner to embedded development

This article sorts out some basic skills in embedded development , All are sorted out according to previous engineering experience , It is suitable for novices who have not done embedded development before .

The embedded development process is generally as follows , Usually in PC The machine Windows Installation under system Ubuntu virtual machine , Build embedded development environment and cross compilation environment , After development , Compile to get bin file , And then in Windows Lower bound bin The file is sent to the embedded board through serial port or network , The program runs on the embedded board .

1、RS232 Serial port connection hole diagram
A serial port , Generally also refers to COM Interface , Slow transmission speed , Suitable for long distance transmission . It is used for data communication between host and embedded version , It is generally used for issuing instructions, etc . According to the agreement standard, it is also divided into RS-232-C、RS-422、RS485 etc. . among RS-232 It is also the most commonly used serial port , Called standard serial port .

The following is just an introduction RS-232 Wiring diagram of .RS232 Serial port is 9 Needle interface , Divided into male head and female head ,PC The serial port on the machine is generally male , Here's the picture .

The functions of each pinhole are as follows ：

The signal line required for the simplest serial interface is 「2 Data sending （TxD）」、「3 Data reception （RxD） and 5 Signally （GnD）」 , Just connect this 3 The upper computer can be realized by one line PC Communication with embedded board , Here's the picture ：

2. Serial communication tool between upper computer and embedded board
In general use SecureCRT Tool for communication between upper computer and board .
（1） A serial port connection
Open quick connect ：

Choice of agreement Serial, The port and baud rate are set according to the actual situation ：

Click to connect , Pop up a new window , Hit enter , The following interface shows that the upper computer is successfully connected with the board .

（2） Use Telnet Connect
Telnet Connecting is using the network （ Network cable ） Realization PC Communication between computer and board , Without serial port .

Tlenet make new connection , choice Telnet agreement ,「 The host name is the name of the board ip.」

Click to connect , Pop up a new window , Enter your username and password ：

3. The upper computer and embedded board realize file transmission
stay SecureCRT Using commands in ifconfig Check the of the board ip Address ：

Connect the upper computer PC The embedded network card is directly connected with the embedded network card , take PC Local connection of the machine ip Change the address to the same network segment as the embedded board , for example ：

Open... In the upper computer tftpd32 Tools , stay Server interface Select the same network segment between the upper computer and the embedded board ip, as follows ：

Attention and so on PC The machine is used as TFTP The server side of the protocol , The board acts as a client .

Download the file from the upper computer to the board , stay SecureCRT Enter the following command ：

here -g From PC Download the file to the board ,-r Represents a remote server （ namely PC） The file of , 1080P.jpg Indicates the file to be transferred , hinder ip The address is PC The machine IP Address , for example ：

After entering the above command , The card receives the file in the current directory . If you need to receive files in a directory , You need to switch to this directory , Then enter the above command .

Transfer the file from the board to the upper computer , stay SecureCRT Enter the following command ：

here -p Push means ,-l Means local （ card ） The file of .
4. Commonly used Linux command
Back to root ：cd /
Unzip the file ：tar -xvf data.tar
Delete file ：rm -f 1.txt
Change the read and write permissions of the directory ：sudo chmod 777 /usr/share/themes explain ： here 777 Means that every user can read and write , The following is the path
rename ：mv aaa.h264 bbb.h264 explain ： take aaa.h264 Rename it to bbb.264
see ip Address ：ifconfig
View file properties ：stat sample_nnie_main
View current path ：pwd
Create folder ：mkdir
change ip Address ：ifconfig eth0 192.168.6.111 ( It will be lost after restart )
5. MP4、AVI And so on .h264 Format *
In embedded systems , Programs often cannot be decoded directly mp4,avi Video files in other formats , It needs to be converted to bare flow .h264 Format , The method is as follows ：

PC Upload and download ffmpeg Tools , Switch to ffmpeg.exe The catalog of , use cmd Open the command line window :

.mp4 turn .h264：

.avi turn .h264:

mov turn h264:

That is to say ffmpeg Generate files in the required format under the directory .

【 Article Welfare 】 Below are some embedded tutorial materials , Interested can learn , You can also join the learning technology exchange group 943552345, Discuss problems with the leaders in the group , You can get a full set of data by joining the group （ Source code attached ）

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