char Rc522Test(void) //获取卡编号函数,返回卡编号1-3,非系统录入卡返回0,没有识别到卡返回-1 { char cardno; if (PcdRequest(0x52, Temp) == MI_OK) //调用寻卡指令 { if (PcdAnticoll(UID) == MI_OK) //获取卡片的序列号信息(也就是卡片的UID) { cardno=0; if(UID[0]==UI0[0]&&UID[1]==UI0[1]&&UID[2]==UI0[2]&&UID[3]==UI0[3]) { cardno=1; } else if(UID[0]==UI1[0]&&UID[1]==UI1[1]&&UID[2]==UI1[2]&&UID[3]==UI1[3]) { cardno=2; } else if(UID[0]==UI2[0]&&UID[1]==UI2[1]&&UID[2]==UI2[2]&&UID[3]==UI2[3]) { cardno=3; } else if(UID[0]==UI3[0]&&UID[1]==UI3[1]&&UID[2]==UI3[2]&&UID[3]==UI3[3]) { cardno=4; } else cardno = 0; } else cardno = -1; } else cardno = -2; return cardno; }解释这段代码
时间: 2023-11-25 07:05:23 浏览: 71
这段代码是一个获取RFID卡片UID并匹配已录入UID的函数,具体解释如下:
首先,该函数调用PcdRequest指令寻找RFID卡片,如果成功,再调用PcdAnticoll指令获取卡片的序列号信息(即UID)。
然后,函数将UID与已录入的UID进行比对,如果匹配成功,则返回对应的卡编号(1-4),否则返回0表示非系统录入卡。
最后,如果寻卡和获取UID的过程中有任何错误,则返回-1或-2表示没有识别到卡或读写错误。
需要注意的是,该函数中使用了全局变量UI0、UI1、UI2、UI3,这些变量应该在其他地方进行初始化并录入系统允许使用的卡片UID。
相关问题
i2c-test -b 2 -s 0x68 -m 1 -rc 5 -d 0x32 0x02 0x04 0x1e 对应的代码
这段命令对应的是使用 i2c 总线读取从设备地址为 0x68 的设备寄存器,寄存器地址为 0x02 的数据,数据长度为 1,重复读取 5 次,每次读取的数据为 0x32 0x02 0x04 0x1e。
下面是使用 C 语言编写的 i2c 读取数据的代码示例:
```c
#include <stdio.h>
#include <fcntl.h>
#include <unistd.h>
#include <linux/i2c-dev.h>
#include <sys/ioctl.h>
int main(void) {
int fd;
char *filename = "/dev/i2c-1"; // i2c 总线设备文件路径
int address = 0x68; // 从设备地址
int reg = 0x02; // 寄存器地址
int len = 1; // 读取数据长度
int repeat = 5; // 重复读取次数
char buf[10] = {0x32, 0x02, 0x04, 0x1e}; // 读取数据缓冲区
// 打开 i2c 总线设备文件
if ((fd = open(filename, O_RDWR)) < 0) {
perror("Failed to open i2c bus");
return 1;
}
// 设置从设备地址
if (ioctl(fd, I2C_SLAVE, address) < 0) {
perror("Failed to set i2c address");
return 1;
}
// 重复读取数据
for (int i = 0; i < repeat; i++) {
// 写入寄存器地址
if (write(fd, ®, 1) != 1) {
perror("Failed to write reg address");
return 1;
}
// 读取数据
if (read(fd, buf, len) != len) {
perror("Failed to read data");
return 1;
}
// 输出读取的数据
printf("Read data: ");
for (int j = 0; j < len; j++) {
printf("%02x ", buf[j]);
}
printf("\n");
}
// 关闭 i2c 总线设备文件
close(fd);
return 0;
}
```
其中,需要注意的是:
- 需要先使用 `open` 函数打开 i2c 总线设备文件,并设置总线地址;
- 使用 `ioctl` 函数设置从设备地址;
- 先写入要读取的寄存器地址,再读取数据;
- 在循环中多次读取数据,直到达到所需的重复次数。
#include <stdio.h> #include "sqlite3.h" static int callback(void* NotUsed, int argc, char** argv, char** azColName) { int i; for (i = 0; i < argc; i++) { printf("%s = %s\n", azColName[i], argv[i] ? argv[i] : "NULL"); } printf("\n"); return 0; } int main(int argc, char** argv) { sqlite3* db; char* zErrMsg = 0; int rc; char* dbfile = "test.db"; char* sql; rc = sqlite3_open(dbfile, &db); if (rc) { fprintf(stderr, "Can't open database: %s\n", sqlite3_errmsg(db)); sqlite3_close(db); return -1; } //在数据库中创建一个名为person的表 sql = "create table person(id int primary key,first_name text,last_name text);"; rc = sqlite3_exec(db, sql, callback, 0, &zErrMsg); if (rc != SQLITE_OK) { fprintf(stderr, "SQL error: %s\n", zErrMsg); sqlite3_free(zErrMsg); } sql = "insert into person values (1,'zhang','san');" "insert into person values (2,'li','si');" "insert into person values (3,'wang','wu');" "insert into person values (4,'zhao','liu');" "insert into person values (5,'sun','qi');"; rc = sqlite3_exec(db, sql, callback, 0, &zErrMsg); if (rc != SQLITE_OK) { fprintf(stderr, "SQL error: %s\n", zErrMsg); sqlite3_free(zErrMsg); } sql = "select * from person where id=3;"; rc = sqlite3_exec(db, sql, callback, 0, &zErrMsg); if (rc != SQLITE_OK) { fprintf(stderr, "Failed to select data: %s\n", zErrMsg); sqlite3_free(zErrMsg); } sql = "delete from person where id=5;"; rc = sqlite3_exec(db, sql, callback, 0, &zErrMsg); if (rc != SQLITE_OK) { fprintf(stderr, "Failed to delete data: %s\n", zErrMsg); sqlite3_free(zErrMsg); } sql = "select * from person;"; rc = sqlite3_exec(db, sql, callback, 0, &zErrMsg); if (rc != SQLITE_OK) { fprintf(stderr, "SQL error: %s\n", zErrMsg); sqlite3_free(zErrMsg); } sqlite3_close(db); return 0; }添加注释
//引入头文件
#include <stdio.h>
#include "sqlite3.h"
//回调函数
static int callback(void* NotUsed, int argc, char** argv, char** azColName) {
int i;
for (i = 0; i < argc; i++) {
printf("%s = %s\n", azColName[i], argv[i] ? argv[i] : "NULL");
}
printf("\n");
return 0;
}
//主函数
int main(int argc, char** argv) {
sqlite3* db;
char* zErrMsg = 0;
int rc;
char* dbfile = "test.db";
char* sql;
rc = sqlite3_open(dbfile, &db); //连接数据库
if (rc) {
fprintf(stderr, "Can't open database: %s\n", sqlite3_errmsg(db));
sqlite3_close(db);
return -1;
}
sql = "create table person(id int primary key,first_name text,last_name text);";
rc = sqlite3_exec(db, sql, callback, 0, &zErrMsg); //创建表
if (rc != SQLITE_OK) {
fprintf(stderr, "SQL error: %s\n", zErrMsg);
sqlite3_free(zErrMsg);
}
sql = "insert into person values (1,'zhang','san');" "insert into person values (2,'li','si');" "insert into person values (3,'wang','wu');" "insert into person values (4,'zhao','liu');" "insert into person values (5,'sun','qi');";
rc = sqlite3_exec(db, sql, callback, 0, &zErrMsg); //插入数据
if (rc != SQLITE_OK) {
fprintf(stderr, "SQL error: %s\n", zErrMsg);
sqlite3_free(zErrMsg);
}
sql = "select * from person where id=3;";
rc = sqlite3_exec(db, sql, callback, 0, &zErrMsg); //查询数据
if (rc != SQLITE_OK) {
fprintf(stderr, "Failed to select data: %s\n", zErrMsg);
sqlite3_free(zErrMsg);
}
sql = "delete from person where id=5;";
rc = sqlite3_exec(db, sql, callback, 0, &zErrMsg); //删除数据
if (rc != SQLITE_OK) {
fprintf(stderr, "Failed to delete data: %s\n", zErrMsg);
sqlite3_free(zErrMsg);
}
sql = "select * from person;";
rc = sqlite3_exec(db, sql, callback, 0, &zErrMsg); //查询数据
if (rc != SQLITE_OK) {
fprintf(stderr, "SQL error: %s\n", zErrMsg);
sqlite3_free(zErrMsg);
}
sqlite3_close(db); //关闭数据库连接
return 0;
}
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