1、查看电脑的串口
~/share/bin/PC$ dmesg | grep tty
[ 0.083244] printk: console [tty0] enabled
[ 0.329145] 00:02: ttyS0 at I/O 0x3f8 (irq = 4, base_baud = 115200) is a 16550A
[ 0.351177] 00:03: ttyS1 at I/O 0x2f8 (irq = 3, base_baud = 115200) is a 16550A
[ 0.420781] tty tty48: hash matches
从回复信息中可以看出电脑有两个串口，分别是ttyS0，ttyS1
USB口的话，信息显示是ttyUSB0
2、添加串口调试代码
简单实现控制灯开的函数
#include <iostream>
#include <string.h>
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <sys/fcntl.h> /*文件控制定义*/
#include <termios.h> /*PPSIX 终端控制定义*/
#include <sys/ioctl.h>
#include <errno.h>
#include <sys/select.h>
#include <sstream>
#include <iomanip>#define ARRAY_SIZE(a) (sizeof(a) / sizeof((a)[0]))using namespace std;static int lightOn();
static int sendRecv(uint8_t *sBuf, uint16_t sSize, uint8_t *rBuf, uint16_t rSize);
static int Open(const char* device, int baudrate, char parity = 'N', int bytesize = 8, int stopbits = 1);
static int set_parity(int fd,int databits,int stopbits,int parity,int baudrate);
int Read(void* buf, size_t maxLen);
int Write(const void* buf, size_t len);
std::string toHex(uint8_t *buf, uint16_t size);int m_fd;int main()
{Open("/dev/ttyS0", 9600);lightOn();return 0;
}int Open(const char* device, int baudrate, char parity/* = 'N'*/, int bytesize/* = 8*/, int stopbits/* = 1*/)
{printf("enter %s\n", __func__);m_fd = ::open(device, O_RDWR | O_NOCTTY | O_NDELAY);if (m_fd < 0){perror("打开COM口时出错");return -1;}//if( set_parity(m_fd,8,1,'N') < 0)if( set_parity(m_fd, bytesize, stopbits, parity, baudrate) < 0){perror("Set Parity Error\n");return -1;}tcflush(m_fd, TCIOFLUSH);printf("leave %s\n", __func__);return 0;
}int set_parity(int fd,int databits,int stopbits,int parity,int baudrate)
{struct termios optnew;speed_t speed = B19200;if ( fd >0 ) {/* Read with blocking behavior */fcntl(fd, F_SETFL, 0);/* Get current option */tcgetattr(fd, &optnew);/* initialize new option to raw input/output */// memset(&optnew, 0, sizeof(optnew));cfmakeraw(&optnew);optnew.c_cc[VMIN ] = 0;optnew.c_cc[VTIME] = 2*10;/* set baudrate */switch (baudrate) {case 1200: speed = B1200; break;case 1800: speed = B1800; break;case 4800: speed = B4800; break;case 9600: speed = B9600; break;case 19200: speed = B19200; break;case 38400: speed = B38400; break;case 57600: speed = B57600; break;case 115200: speed = B115200; break;default: speed = B19200; break;}cfsetispeed(&optnew, speed);cfsetospeed(&optnew, speed);/* Set data bits */optnew.c_cflag &= ~CSIZE;optnew.c_cflag &= ~CRTSCTS;optnew.c_iflag &= ~(ICRNL|IXON);optnew.c_cflag |= CLOCAL | CREAD;optnew.c_oflag &= ~OPOST;switch (databits) {case 5: optnew.c_cflag |= CS5; break;case 6: optnew.c_cflag |= CS6; break;case 7: optnew.c_cflag |= CS7; break;default :optnew.c_cflag |= CS8; break;}/* Set parity checking */optnew.c_cflag |= PARENB;switch (parity) {case 'e':case 'E': optnew.c_cflag &= ~PARODD; break;case 'o':case 'O': optnew.c_cflag &= PARODD; break;default :optnew.c_cflag &= ~PARENB; break;}/* Set stop bit(s) */if (stopbits == 2)optnew.c_cflag &= CSTOPB;elseoptnew.c_cflag &= ~CSTOPB;optnew.c_lflag &= ~( ICANON | ECHO | ECHOE | ISIG );/* Apply new option */tcsetattr(fd, TCSANOW, &optnew);}return fd;
}int lightOn()
{uint8_t send[] = {0x2A, 0x4B, 0x0D};uint8_t right[] = {0x2A, 0x4B, 0x00, 0x0D};int retry = 2;while(retry--){uint8_t recv[sizeof(right)];memset(recv, 0, sizeof(right));printf("send %s\n", toHex((uint8_t *)send, sizeof(send)).c_str());const int recvCount = sendRecv(send, sizeof(send), recv, sizeof(recv));if(recvCount != sizeof(recv)){if(recvCount){printf("recv %s\n", toHex((uint8_t *)recv, sizeof(recv)).c_str());}continue;}if(0 != memcmp(right, recv, sizeof(right))){printf("recv %s\n", toHex((uint8_t *)recv, sizeof(recv)).c_str());continue;}//successprintf("recv %s\n", toHex((uint8_t *)recv, sizeof(recv)).c_str());retry = 0;break;}return retry;
}int sendRecv(uint8_t *sBuf, uint16_t sSize, uint8_t *rBuf, uint16_t rSize)
{printf("enter %s\n", __func__);// m_mutex.lock();int ret = Write(sBuf, sSize);if (ret != 0){printf("%s Write error, Buf:%s\n", __func__, sBuf);goto _RET;}ret = Read(rBuf, rSize);if (ret != rSize){printf("%s read:%s ret:%d\n", __func__, rBuf, ret);goto _RET;}_RET:
// m_mutex.unlock();return ret;
}int Write(const void* buf, size_t len)
{printf("enter %s\n", __func__);int ret = 0;int n = ::write(m_fd, buf, len);if(n != len){ret = -2;}
// printf("send to uart result:%i\n", ret);return ret;
}/** return 接受到的字节数*/
int Read(void* buf, size_t maxLen)
{printf("enter %s\n", __func__);int offset = 0;while(offset < maxLen){fd_set rd;FD_ZERO(&rd);FD_SET(m_fd, &rd);timeval timeout;timeout.tv_sec = 1;int ready = select(m_fd+1, &rd, NULL, NULL, &timeout);if (ready == 0){ //timeout
// offset = SER_TO;printf("timeout\n");break;}else if (ready == -1 && (errno != EINTR) ){ //erroroffset = -2;printf("error\n");break;}else if(ready == 1){if (FD_ISSET(m_fd, &rd)){int n = ::read(m_fd, buf + offset, maxLen - offset);if(n > 0){offset += n;}}}}return offset;
}std::string toHex(uint8_t *buf, uint16_t size)
{std::stringstream hexSS;for (int i = 0; i < size; i++){hexSS << std::setw(2) << std::setfill('0') << std::hex << (int)buf[i] << " ";}std::string hexStr = hexSS.str();return hexStr;
}
3、遇到open函数出错
在::open() 出错时，已经通过perror函数打印出出错信息，可以根据信息修改
1）比如报错信息提示权限不对，修改权限
chmod 666 /dev/ttyS0或者以root权限运行可执行文件
// 假如可执行文件是a.out
sudo ./a.out
2）检查串口波特率
~/share/bin/PC$ stty -F /dev/ttyS0
speed 9600 baud; line = 0;
min = 0; time = 20;
-brkint -icrnl -imaxbel
-opost
-isig -icanon -iexten -echo -echoe
