Raspberry pie - environment settings and cross compilation

One 、 Raspberry pie VNC Viewer Remote connection by

1. The tools we need are raspberry pie , Formatting tool ,VNC Viewer, Image burning tool , Remote connection tools
Raspberry pie （ Official website ）：https://www.raspberrypi.org/downloads/raspbian/
Formatting tool ：SDCardFormatterv5（ Software ）
VNC Viewer（ Official website ）：https://www.realvnc.com/en/connect/download/viewer/
Image burning tool ： Raspberry Pi（ Software ）
Remote connection tools （ Official website ）：https://www.chiark.greenend.org.uk/~sgtatham/putty/
If you don't understand, you can refer to ：https://blog.csdn.net/qq_43279579/article/details/109142276

2.SD Card format
（1） take SD Insert into the card reader , Then plug the card reader into the computer .
（2） Open the formatting tool SDCardFormatterv5.
（3） Select what you want to format SD card .
（4） Select the dialog box that pops up , choice “ yes ”.
（5） And then it pops up , Prompt for formatting completion , Select OK , It's done. SD Card formatting .
3. Burn image
（1） Open the burning tool raspberry pi.
（2） Click on “CHOOSE OS”, Select the image file you just downloaded , And then click “CHOOSE SD CARD” Select the just formatted SD card , Then click WRITE.
（3） Then a dialog box will pop up , choice “Continue/OK”, then , And started burning .
4. configure network
（1） On the computer , Open the burning image just now SD card .
（2） stay boot Under the table of contents , Build a ssh Empty file .
（3） stay boot Under the table of contents , Create a text file first .
（4） open the text file , Copy the following into the text .

country=CN
ctrl_interface=DIR=/var/run/wpa_supplicant GROUP=netdev
update_config=1

network={
    
	ssid=" Your wireless network name "
	psk=" Your wireless password "
	key_mgmt=WPA-PSK
	priority=1
}

（5） Save the text just now , And change the name to wpa_supplicant.conf.
（6） Take out SD card , take SD Insert the card into the raspberry pie , Turn on the phone hotspot and connect the raspberry pie at the same time .
（7） You can check the raspberry pie on your mobile phone ip Address .
5.putty Remote connection
（1） open putty, stay Host Name It's about , Enter the results you just viewed IP Address , Then choose “open”.
（2） Select the dialog box that pops up , choice “ no ”.
（3） Enter the user and password （ Default user ：pi The default password ：raspberry）.
（4） Start raspberry pie VNC service , Input instruction （sudo raspi-config）, Configure raspberry pie .
（5） Select... With the up and down keys “Interfacing Options”, Then press the left and right keys to select “Select”.
（6） Then press the up and down keys to select “VNC”, Press the left and right keys to select “Select”.
（7）“would you like the vNc server to be enabled?”–> choice “Yes”.
（8）“The VNC server is enabled”–> Carriage return option “OK”.
（9） Up and down key selection “Advanced Options”, Press the left and right keys to select “Select”.
（10） Up and down key selection “Resolution”, Press the left and right keys to select “Select”.
（11） Then there is the resolution selection , choice “DMT Mode 16”, Then choose “OK”.
（12）“The resolution is set to DMT mode 16”–> Carriage return option “OK”.
（13） Back to the beginning , choice “Finish”, complete .
6.VNC Viewer Remote interface display
Open after installation VNC Viewer Interface , First enter the name of raspberry pie at the top IP Address , Then enter... In the pop-up interface Username,Password, Click on “OK”.

Two 、assert（ Assertion ）

assert（） It is generally called assertion , It is a macro that is often used when debugging programs . It is defined in <assert.h> Header file , It is usually used to judge whether there is illegal data in the program , When the program runs, it evaluates the expression in parentheses .
It should be noted that ,assert（） Only in Debug Version has , Compilation of Release Version is ignored .
The other thing to note is that assert（） And asser() The difference between ,assert() It's a macro , and assert（） yes ANSIC Functions specified in the standard , It is associated with assert（） Similar function of , But it can be applied to Release In the version , Use assert（） The disadvantage of , Frequent calls will greatly affect the performance of the program , Add extra expenses .

assert The definition of macro is as follows

#define assert(ignore) ((void)0)

3、 ... and 、 Raspberry pie Executive .c file

First use putty Raspberry pie , And then use （nano helloworld.c） Command create file , use gcc Tool compilation （gcc helloworld.c） For output （./a.out）
The document code is as follows

#include <assert.h>
#include <stdio.h>
 
int main()
{
    
   int a;
   char str[50];
     
   printf(" Please enter an integer value ： ");
   scanf("%d", &a);
   assert(a >= 10);
   printf(" The integer entered is ： %d\n", a);
    
   printf(" Please enter the string ： ");
   scanf("%s", str);
   assert(str != NULL);
   printf(" The input string is ： %s\n", str);
    
   return(0);
}

Four 、 use scp command , Practice in Ubuntu Copy and transfer files between the system and the raspberry pie system .

1. Create a example.txt file

2. Enter the command “sudo nano /etc/ssh/sshd_config”, Then remove the "PermitRootLogin prohibit-password " Previous comments , Save and exit .
![ Insert picture description here ](https://img-
3. Enter the command after restart “systemctl restart sshd”, If yes （Failed to start sshd.service: Unit sshd.service not found.） error , Add the input command first “systemctl enable ssh.service”, And then restart . use

scp /home/example.txt [email protected]192.168.75.1:/home/JingL  //@ I made my own raspberry pie IP Address 

Copy it in raspberry pie

4, In raspberry pie ls Command to see if there is example.txt file , Use nano example.txt Command to open view ：

ls 

nano example.txt

5、 ... and 、 Reference link

https://blog.csdn.net/qq_45659777/article/details/125347172?spm=1001.2014.3001.5501
https://blog.csdn.net/qq_43279579/article/details/109142276