从套接字读取SocketCAN仅返回11cobid
从套接字读取SocketCAN仅返回11cobid
提问于 2020-10-27 17:01:53
我正在尝试从socketCAN中读取，并且总是为11位标识符过滤msg。这应该是一个为29位标识符设置rpoper标志的问题，但我找不到有人可以帮助的地方……
struct can_frame message;
struct sockaddr_can addr;
struct ifreq ifr;
int fd = -1; // file descriptor (it´s a socket)
if((fd = socket(PF_CAN, SOCK_RAW, CAN_RAW)) < 0)
{
LE_INFO("cannot open socket");
return;
}
strcpy(ifr.ifr_name, "can0");
ioctl(fd, SIOCGIFINDEX, &ifr);
addr.can_family = AF_CAN;
addr.can_ifindex = ifr.ifr_ifindex;
if(bind(fd, (struct sockaddr *)&addr, sizeof(addr)) < 0)
{
printf("cannot bind socket\n");
return;
}
uint8_t nbytes;
message.can_id |= CAN_EFF_FLAG;
while(1)
{
nbytes = read(fd, &message, sizeof(struct can_frame));
if (nbytes < 0) {
perror("can raw socket read");
return;
}
/* paranoid check ... */
if (nbytes < sizeof(struct can_frame)) {
fprintf(stderr, "read: incomplete CAN frame\n");
return;
}
printf("READ COB_ID:%x\n",message.can_id | CAN_EFF_FLAG);
}
return;我正在发送一个带有idx x901的CAN帧，下面是打印的内容：
阅读COB_ID:80000101
阅读COB_ID:80000101
阅读COB_ID:80000101
我已经用许多不同的方法解决了这个问题，似乎C代码工作正常，但我怀疑问题出在mcp251x的内核模块上，它没有正确地接收扩展标志？或者在运行内核模块之前需要进行一些初始化？
提前感谢任何能帮上忙的人。
回答 1
Stack Overflow用户
回答已采纳
发布于 2021-06-11 16:31:39
您对CAN标志和过滤的理解不正确。看一看linux can.h的摘录：
/* special address description flags for the CAN_ID */
#define CAN_EFF_FLAG 0x80000000U /* EFF/SFF is set in the MSB */
#define CAN_RTR_FLAG 0x40000000U /* remote transmission request */
#define CAN_ERR_FLAG 0x20000000U /* error message frame */
/* valid bits in CAN ID for frame formats */
#define CAN_SFF_MASK 0x000007FFU /* standard frame format (SFF) */
#define CAN_EFF_MASK 0x1FFFFFFFU /* extended frame format (EFF) */
#define CAN_ERR_MASK 0x1FFFFFFFU /* omit EFF, RTR, ERR flags */下面是一个同时适用于SFF和EFF消息的示例：
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <net/if.h>
#include <sys/ioctl.h>
#include <sys/socket.h>
#include <linux/can.h>
#include <linux/can/raw.h>
int main(int argc, char **argv)
{
struct can_frame message;
struct sockaddr_can addr;
struct ifreq ifr;
int fd = -1; // file descriptor (it´s a socket)
if((fd = socket(PF_CAN, SOCK_RAW, CAN_RAW)) < 0)
{
printf("cannot open socket");
return -9;
}
strcpy(ifr.ifr_name, "vcan0");
ioctl(fd, SIOCGIFINDEX, &ifr);
addr.can_family = AF_CAN;
addr.can_ifindex = ifr.ifr_ifindex;
if(bind(fd, (struct sockaddr *)&addr, sizeof(addr)) < 0)
{
printf("cannot bind socket\n");
return -1;
}
u_int8_t nbytes;
message.can_id |= CAN_EFF_FLAG | CAN_RTR_FLAG | CAN_EFF_MASK;
while(1)
{
nbytes = read(fd, &message, sizeof(struct can_frame));
if (nbytes < 0) {
perror("can raw socket read");
return -2;
}
/* paranoid check ... */
if (nbytes < sizeof(struct can_frame)) {
fprintf(stderr, "read: incomplete CAN frame\n");
return -3;
}
printf("READ COB_ID: %x\n", message.can_id & CAN_EFF_MASK);
}
return 0;
}现在发送这些消息：
cansend vcan0 00000123#FFFFFFFFFFFFFFFF
cansend vcan0 12345678#FFFFFFFFFFFFFFFF给出正确的输出：
READ COB_ID: 123
READ COB_ID: 12345678页面原文内容由Stack Overflow提供。腾讯云小微IT领域专用引擎提供翻译支持
原文链接：
https://stackoverflow.com/questions/64551075
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