personalNote

Precautions For Inter-core Data Transfer

the cache needs to be especially careful because it can cause your data to be accessed incorrectly. If core A needs to access the memory of core B, this section of core B memory needs to be careful if there is a cache, which is generally not recommended 

SPI调试总结

SPI时序可能出现问题，需要用逻辑分析仪Kingst VIS或者示波器查看波形变化，为什么出现延时情况，读写寄存器为什么会出现这么大的时间延时。结果发现和系统调用有很大的关系，xxx.elf的进程在运行过程中采用的是默认的优先级配置的nice值默认为0，会出现被抢占的情况，所以整体的延时会出现60us的情况。正常情况下是7-8us.整个配置MMIC的时间。

知乎学习链接

https://www.zhihu.com/people/ljgibbs/posts

https://www.zhihu.com/people/lgjjeff

‘’’C
//tcp server,can reconnection and recv data from tcp client
#include <stdio.h>
#include <sys/socket.h>
#include <arpa/inet.h>
#include <unistd.h>
#include <string.h>
#include <fcntl.h>

#define PORT 11011
#define IP_ADDR “192.168.30.60”

int main(){

int server_fd, client_fd;
struct sockaddr_in server_addr,client_addr; 

// 创建 socket
server_fd = socket(AF_INET, SOCK_STREAM, 0);
if(server_fd < 0){
    printf("Error creating socket!");
    return 1;
}

// 设置地址与端口信息
server_addr.sin_family = AF_INET;
server_addr.sin_addr.s_addr = inet_addr(IP_ADDR); 
server_addr.sin_port = htons(PORT);

// 绑定socket与地址信息 
if(bind(server_fd, (struct sockaddr*)&server_addr, sizeof(server_addr)) < 0){
   printf("Bind failed!");
   return 1;
}

// 开始监听
if (listen(server_fd, 5) < 0){
    printf("Listen failed!");
    return 1;
}
 
while(1){
    socklen_t client_len = sizeof(client_addr);
      // 等待客户端连接请求 
    client_fd = accept(server_fd, (struct sockaddr*)&client_addr, &client_len);
      if(client_fd < 0){
      continue;
      }
    
    // 设置 client_fd 为非阻塞模式
    fcntl(client_fd, F_SETFL, O_NONBLOCK);
  
       while(1){

        // 尝试接收数据
        char buffer[1024];        
        int byte_num = recv(client_fd, buffer, 1024, 0);
        // 连接已关闭
        if(byte_num == 0){
            close(client_fd);
            break;
        }
      
        // 打印接收到的数据
        //if(byte_num > 0){
          //  printf("Received data: %s", buffer); 
        //}

        // 遍历缓冲区每个字节
        for(int i=0; i < byte_num; i++) {

            // 将字节转换为整数打印 
            printf("%x ", (int)buffer[i]); 

        } 

        printf("\n");


    }

    // 关闭客户端 socket
    close(client_fd); 
}

return 0;

}
‘’’