基于ROS和beaglebone的串口通信方式，使用键盘控制移动机器人

2023-07-30 11:09:40

一、所需工具包

1.ROS键盘包：teleop_twist_keyboard
2.ROS串口通讯包：serial

$ cd ~/catkin_ws/src
$ git clone https://github.com/Forrest-Z/teleop_twist_keyboard.git
$ git clone https://github.com/Forrest-Z/serial.git
$ catkin_make

3.在ubuntu的ros中建立一个ros_car_pkg包:

$ cd ~/catkin_ws/src
$ catkin_create_pkg ros_car_pkg roscpp rospy std_msgs

4.新建 base_controller 文件:

$ cd catkin_ws/src/base_controller
$ mkdir src
$ vim src/base_controller.cpp

代码如下:
   /
   串口通信说明：
   1.写入串口
   （1）内容：左右轮速度，单位为mm/s
   （2）格式：10个字节,[右轮速度４字节][左轮速度４字节][结束符"\n"1个字节]
   2.读取串口
   （1）内容：小车线速度，角速度，单位依次为：mm/s,rad/s
   */

#include "ros/ros.h"
#include <geometry_msgs/Twist.h>
#include <string>
#include <iostream>
#include <cstdio>
#include <unistd.h>
#include <math.h>
#include "serial/serial.h"
using std::ios;
using std::string;
using std::exception;
using std::cout;
using std::cerr;
using std::endl;
using std::vector;
float ratio = 1000.0f ; //转速转换比例，执行速度调整比例
float D = 0.2680859f ; //两轮间距，单位是m
float linear_temp=0,angular_temp=0;//暂存的线速度和角速度
unsigned char data_terminal=0x0a; //“/n"字符
unsigned char speed_data[9]={0}; //要发给串口的数据
union floatData //union的作用将较大的对象分解成组成这个对象的各个字节
{
float d;
unsigned char data[4];
}right_speed_data,left_speed_data;
/************************************************************/
void callback(const geometry_msgs::Twist& cmd_input)//订阅/cmd_vel主题回调函数
{
string port("/dev/ttyUSB0"); //小车串口号
unsigned long baud = 115200; //小车串口波特率
serial::Serial my_serial(port, baud, serial::Timeout::simpleTimeout(1000)); //配置串口
angular_temp = cmd_input.angular.z ;//获取/cmd_vel的角速度,rad/s
linear_temp = cmd_input.linear.x ;//获取/cmd_vel的线速度.m/s
//将转换好的小车速度分量为左右轮速度
left_speed_data.d = linear_temp- 0.5f*angular_temp*D ;
right_speed_data.d = linear_temp+ 0.5f*angular_temp*D ;
//存入数据到要发布的左右轮速度消息
left_speed_data.d*=ratio; //放大１０００倍，mm/s
right_speed_data.d*=ratio;//放大１０００倍，mm/s
cout<<"angular_temp = "<< angular_temp << endl;
cout<<"linear_temp = "<< linear_temp<<endl;
cout<<"left_speed_data.d = "<< left_speed_data.d<<endl;
cout<<"right_speed_data.d = "<< right_speed_data.d << endl;
for(int i=0;i<4;i++) //将左右轮速度存入数组中发送给串口
{
speed_data[i]=right_speed_data.data[i];
speed_data[i+4]=left_speed_data.data[i];
}
//在写入串口的左右轮速度数据后加入”/n“
speed_data[8]=data_terminal;
//speed_data[9]=data_terminal1;
//写入数据到串口
for(int i=0;i<9;i++){
cout.setf(ios::hex,ios::basefield);//设置十六进制显示数值
cout.setf(ios::showbase|ios::uppercase);//设置0x头和大写
cout<<"s_i = "<<(int)speed_data[i]<<endl;
}
my_serial.write(speed_data,10);
}
int main(int argc, char **argv)
{
ros::init(argc, argv, "base_controller");
ros::NodeHandle n;
ros::Subscriber sub = n.subscribe("cmd_vel", 20, callback); //订阅cmd_vel主题
ros::spin();//周期执行
return 0;
}

修改CMakeList.txt:

cmake_minimum_required(VERSION 2.8.3)
project(ros_car_pkg)
find_package(catkin REQUIRED COMPONENTS
message_generation
roscpp
rospy
std_msgs
serial
tf
nav_msgs
)
include_directories(
# include
${catkin_INCLUDE_DIRS}
${serial_INCLUDE_DIRS}
)
add_message_files(FILES MsgCar.msg)
generate_messages(DEPENDENCIES std_msgs)
add_executable(base_controller src/base_controller.cpp)
target_link_libraries(base_controller ${catkin_LIBRARIES})
add_dependencies(base_controller ros_car_pkg_generate_messages_cpp)
catkin_package(CATKIN_DEPENDS roscpp rospy std_msgs)

单独编译ros_car_pkg包:

$ catkin_make -DCATKIN_WHITELIST_PACKAGES='ros_car_pkg'

二、控制原理：

当我们按下键盘时，teleop_twist_keyboard 包会发布 /cmd_vel 发布速度主题
在 base_controller 节点订阅这个话题，接收速度数据，转换成字节数据，然后写入串口
通过USB转串口线，连接到板子的UART串口，在beaglebone中读取串口数据
将串口数据转换成pwm信号，并加载设备树，控制电机运转，从而实现键盘控制小车的移动

1.设置beaglebone串口：

查询手册，选择UART4，其中TXD(发送数据引脚)为P9-13，RXD(接受数据引脚)p9-11
实验室的usb转串口线为：蓝色对应数据接受端，接RXD;白色对应发送数据端，接TXD，黑色和红色一定要悬空！！！
将串口线的USB端插上电脑，启动板子，在ubuntu中登录板子

$ ssh root@192.168.7.2
   测试的时候先手动加载UART4设备树(后面串口配置成功之后,可以通过程序直接启动）
       $ cd /sys/devices/bone_capemgr.9/
       $ echo BB-UART4 > slots
       $ cat slots
   如果加载成功，在/dev下会出现ttyO4串口
       $ cd /dev
       $ ls tty*
   先使用screen或者minicom监测该串口
       $ sudo screen /dev/ttyO4 115200

设置ubuntu中的ros串口：
   如果usb转串口线没坏的话，在/dev下看到ttyUSB0
       $ cd /dev
       $ ls tty*
       $ sudo chmod 666 /dev/ttyUSB0
   如果该步骤设置成功的话，通过往ros串口发数据，可以在上述screen监测的串口看到发送的数据
       $ echo "Hello HFUT" > /dev/ttyUSB0

至此，串口设置完成

三、建立ros通信：

1.ubuntu中的ros端操作：

$ roscore
$ rosrun teleop_twist_keyboard teleop_twist_keyboard.py
$ rosrun ros_car_pkg base_controller

2.beaglebone终端操作:
运行代码加载设备树并读串口数据用于控制PWM，进而控制小车运动

#include<stdio.h>
#include<fcntl.h>
#include<unistd.h>
#include<termios.h>
#define SLOTS "/sys/devices/bone_capemgr.9/slots"
int main()
{
int fd, count_r,count_t,i;
unsigned char buff[100]; // the reading & writing buffer
struct termios opt; //uart confige structure
//加载设备树
if ((fd = open(SLOTS, O_WRONLY)) < 0)
{
perror("SLOTS: Failed to open the file. \n");
return -1;
}
if ((count_t = write(fd, "BB-UART4",8))<0) //8ge zi fu
{
perror("SLOTS:Failed to write to the file\nFailed to mount the UART4");
return -1;
}
close(fd);
//设置串口
if ((fd = open("/dev/ttyO4", O_RDWR | O_NOCTTY )) < 0)
{
perror("UART: Failed to open the UART device:ttyO4.\n");
return -1;
}
tcgetattr(fd, &opt); // get the configuration of the UART
opt.c_cflag = B115200| CS8 | CREAD | CLOCAL;
// 115200 baud, 8-bit, enable receiver, no modem control lines
opt.c_iflag = IGNPAR | ICRNL;
// ignore partity errors, CR -> newline
opt.c_iflag &= ~(IXON | IXOFF | IXANY);
//turn off software stream control
opt.c_lflag &= ~(ICANON | ECHO | ECHOE | ISIG);
tcflush(fd,TCIOFLUSH); // 清理输入输出缓冲区
tcsetattr(fd, TCSANOW, &opt); // changes occur immmediately
//读串口
while(1)
{
if ((count_r = read(fd,(void*)buff,100))<0){
perror("ERR:No data is ready to be read\n");
return -1;
}
if (count_r == 0){
printf("ERR:No data is ready to be read\n");
}
else
{
printf("The following was read in [%d]:%X\n",count_r,buff); //具体格式是字节
}
//发送PWM
if (buff != NULL)
{
if ((fd = open(SLOTS, O_WRONLY)) < 0)
{
perror("SLOTS: Failed to open the file. \n");
return -1;
}
if ((count_t = write(fd, "bone_pwm_P9_22",14))<0) //8ge zi fu
{
perror("SLOTS:Failed to write to the file\nFailed to mount the bone_pwm_P9_22");
return -1;
}
if ((count_t = write(fd, "bone_pwm_P9_16",14))<0) //8ge zi fu
{
perror("SLOTS:Failed to write to the file\nFailed to mount the bone_pwm_P9_16");
return -1;
}
if ((count_t = write(fd, "am33xx_pwm",10))<0) //8ge zi fu
{
perror("SLOTS:Failed to write to the file\nFailed to mount the PWM");
return -1;
}
close(fd);
if ((fd = open(p922,O_WRONLY))<0)
{
perror("p922: Failed to open the file. \n");
return -1;
}
if((count_t= write(fd,"1",1))<0) //8ge zi fu
{
perror("p922run:Failed to write to the file\nFailed to mount the p9223");
return -1;
}
close(fd);
if ((fd = open(p916,O_WRONLY))<0)
{
perror("p916: Failed to open the file. \n");
return -1;
}
if((count_t= write(fd,"1",1))<0) //8ge zi fu
{
perror("p916run:Failed to write to the file\nFailed to mount the p9223");
return -1;
}
close(fd);
usleep(50000000);
}
return 0;
}

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