Raspberry pi2串口通信

安装pyserial的串口库，$ wget  http://downloads.sourceforge.net/project/pyserial/pyserial/2.7/pyserial-2.7.tar.gz

下载后，对压缩文件解压：

$ tar zxvf  ./pyserial-2.7.tar.gz

$ cd pyserial

$ sudo python setup.py  install

用命令查找串口设备

$ dmesg | grep tty*

打开python交互运行环境

 $ python

>>> import serial

>>> ser = serial.Serial('/dev/ttyUSB0',115200)

>>> while 1:

.... ser.readlin()

>>>ser.write('this is string')

连接到PC端串口调试助手，打印

Communication with ROS through USART Serial Port   

$ cd ~/catkin_ws/src$ catkin_create_pkg r2SerialDriver std_msgs rospy roscpp$ cd ~/catkin_ws$ catkin_make

To add the workspace to your ROS environment you need to source the generated setup file:

$ . ~/catkin_ws/devel/setup.bash$ cd ~/catkin_ws/src/r2SerialDriver/src

Add a file: "r2Serial.cpp", Source code:

1. 

3. /*                                                                                                                        * Copyright (c) 2010, Willow Garage, Inc.                                                                                * All rights reserved.                                                                                                   *                                                                                                                        * Redistribution and use in source and binary forms, with or without                                                     * modification, are permitted provided that the following conditions are met:                                            *                                                                                                                        *     * Redistributions of source code must retain the above copyright                                                   *       notice, this list of conditions and the following disclaimer.                                                    *     * Redistributions in binary form must reproduce the above copyright                                                *       notice, this list of conditions and the following disclaimer in the                                              *       documentation and/or other materials provided with the distribution.                                             *     * Neither the name of the Willow Garage, Inc. nor the names of its                                                 *       contributors may be used to endorse or promote products derived from                                             *       this software without specific prior written permission.                                                         *                                                                                                                        * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"                                            * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE                                              * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE                                             * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE                                               * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR                                                    * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF                                                   * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS                                               * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN                                                * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)                                                * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE                                             * POSSIBILITY OF SUCH DAMAGE.                                                                                            *///r2Serial.cpp// communicate via RS232 serial with a remote uController. // communicate with ROS using String type messages.// subscribe to command messages from ROS// publish command responses to ROS// program parameters - ucontroller# (0,1), serial port, baud rate//Thread main//  Subscribe to ROS String messages and send as commands to uController//Thread receive//  Wait for responses from uController and publish as a ROS messages#include "ros/ros.h"#include "std_msgs/String.h"#include <sstream>#include <pthread.h>#include <sys/types.h>#include <sys/stat.h>#include <sys/time.h>#include <fcntl.h>#include <termios.h>#include <stdio.h>#include <stdlib.h>#define DEFAULT_BAUDRATE 19200#define DEFAULT_SERIALPORT "/dev/ttyUSB0"//Global dataFILE *fpSerial = NULL;   //serial port file pointerros::Publisher ucResponseMsg;ros::Subscriber ucCommandMsg;int ucIndex;          //ucontroller index number//Initialize serial port, return file descriptorFILE *serialInit(char * port, int baud){  int BAUD = 0;  int fd = -1;  struct termios newtio;  FILE *fp = NULL; //Open the serial port as a file descriptor for low level configuration // read/write, not controlling terminal for process,  fd = open(port, O_RDWR | O_NOCTTY | O_NDELAY );  if ( fd<0 )  {    ROS_ERROR("serialInit: Could not open serial device %s",port);    return fp;  }  // set up new settings  memset(&newtio, 0,sizeof(newtio));  newtio.c_cflag =  CS8 | CLOCAL | CREAD;  //no parity, 1 stop bit  newtio.c_iflag = IGNCR;    //ignore CR, other options off  newtio.c_iflag |= IGNBRK;  //ignore break condition  newtio.c_oflag = 0;        //all options off  newtio.c_lflag = ICANON;     //process input as lines  // activate new settings  tcflush(fd, TCIFLUSH);  //Look up appropriate baud rate constant  switch (baud)  {     case 38400:     default:        BAUD = B38400;        break;     case 19200:        BAUD  = B19200;        break;     case 9600:        BAUD  = B9600;        break;     case 4800:        BAUD  = B4800;        break;     case 2400:        BAUD  = B2400;        break;     case 1800:        BAUD  = B1800;        break;     case 1200:        BAUD  = B1200;        break;  }  //end of switch baud_rate  if (cfsetispeed(&newtio, BAUD) < 0 || cfsetospeed(&newtio, BAUD) < 0)  {    ROS_ERROR("serialInit: Failed to set serial baud rate: %d", baud);    close(fd);    return NULL;  }  tcsetattr(fd, TCSANOW, &newtio);  tcflush(fd, TCIOFLUSH);  //Open file as a standard I/O stream  fp = fdopen(fd, "r+");  if (!fp) {    ROS_ERROR("serialInit: Failed to open serial stream %s", port);    fp = NULL;  }  return fp;} //serialInit//Process ROS command message, send to uControllervoid ucCommandCallback(const std_msgs::String::ConstPtr& msg){  ROS_DEBUG("uc%dCommand: %s", ucIndex, msg->data.c_str());  fprintf(fpSerial, "%s", msg->data.c_str()); //appends newline} //ucCommandCallback//Receive command responses from robot uController//and publish as a ROS messagevoid *rcvThread(void *arg){  int rcvBufSize = 200;  char ucResponse[rcvBufSize];   //response string from uController  char *bufPos;  std_msgs::String msg;  std::stringstream ss;  ROS_INFO("rcvThread: receive thread running");  while (ros::ok()) {    bufPos = fgets(ucResponse, rcvBufSize, fpSerial);    if (bufPos != NULL) {      ROS_DEBUG("uc%dResponse: %s", ucIndex, ucResponse);      msg.data = ucResponse;      ucResponseMsg.publish(msg);    }  }  return NULL;} //rcvThreadint main(int argc, char **argv){  char port[20];    //port name  int baud;     //baud rate   char topicSubscribe[20];  char topicPublish[20];  pthread_t rcvThrID;   //receive thread ID  int err;  //Initialize ROS  ros::init(argc, argv, "r2SerialDriver");  ros::NodeHandle rosNode;  ROS_INFO("r2Serial starting");  //Open and initialize the serial port to the uController  if (argc > 1) {    if(sscanf(argv[1],"%d", &ucIndex)==1) {      sprintf(topicSubscribe, "uc%dCommand",ucIndex);      sprintf(topicPublish, "uc%dResponse",ucIndex);    }    else {      ROS_ERROR("ucontroller index parameter invalid");      return 1;    }  }  else {    strcpy(topicSubscribe, "uc0Command");    strcpy(topicPublish, "uc0Response");  }  strcpy(port, DEFAULT_SERIALPORT);  if (argc > 2)     strcpy(port, argv[2]);  baud = DEFAULT_BAUDRATE;  if (argc > 3) {    if(sscanf(argv[3],"%d", &baud)!=1) {      ROS_ERROR("ucontroller baud rate parameter invalid");      return 1;    }  }  ROS_INFO("connection initializing (%s) at %d baud", port, baud);   fpSerial = serialInit(port, baud);  if (!fpSerial )  {    ROS_ERROR("unable to create a new serial port");    return 1;  }  ROS_INFO("serial connection successful");  //Subscribe to ROS messages  ucCommandMsg = rosNode.subscribe(topicSubscribe, 100, ucCommandCallback);  //Setup to publish ROS messages  ucResponseMsg = rosNode.advertise<std_msgs::String>(topicPublish, 100);  //Create receive thread  err = pthread_create(&rcvThrID, NULL, rcvThread, NULL);  if (err != 0) {    ROS_ERROR("unable to create receive thread");    return 1;  }  //Process ROS messages and send serial commands to uController  ros::spin();  fclose(fpSerial);  ROS_INFO("r2Serial stopping");  return 0;}

Modify the CMakeList.txt file:

$ cd ~/catkin_ws/src/r2SerialDriver$ gedit CMakeList.txt

add/modify these lines as below:

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print?

1. find_package(catkin REQUIRED COMPONENTS  
2.   roscpp  
3.   rospy  
4.   std_msgs  
5. )  
6.   
7. include_directories(  
8.   ${catkin_INCLUDE_DIRS}  
9. )  
10.   
11. add_executable(r2SerialDriver src/r2Serial.cpp)  
12.   
13. add_dependencies(r2SerialDriver ${${PROJECT_NAME}_EXPORTED_TARGETS} ${catkin_EXPORTED_TARGETS})  
14.   
15. target_link_libraries(r2SerialDriver  
16.    ${catkin_LIBRARIES}  
17.  )  

Save and Build the package again:

$ cd ~/catkin_ws$ catkin_make -DCMAKE_BUILD_TYPE=Release 

He also offered a simple launch file that interfaces to two microcontrollers using two serial connections, put the code into
  "~/catkin_ws/src/r2SerialDriver/launch/r2SerialDriver.launch" file:

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print?

1. <launch>  
2.   <node pkg="r2SerialDriver" type="r2SerialDriver" name="r2Serial0" args="0 /dev/ttyUSB0 9600" output="screen" >  
3.   <remap from="ucCommand" to="uc0Command" />  
4.   <remap from="ucResponse" to="uc0Response" />  
5.   </node>  
6.   
7.   <node pkg="r2SerialDriver" type="r2SerialDriver" name="r2Serial1" args="1 /dev/ttyUSB1 9600" output="screen" >  
8.   <remap from="ucCommand" to="uc1Command" />  
9.   <remap from="ucResponse" to="uc1Response" />  
10.   </node>  
11.   
12. </launch>  

<launch>  <node pkg="r2SerialDriver" type="r2SerialDriver" name="r2Serial0" args="0 /dev/ttyUSB0 9600" output="screen" >  <remap from="ucCommand" to="uc0Command" />  <remap from="ucResponse" to="uc0Response" />  </node>  <node pkg="r2SerialDriver" type="r2SerialDriver" name="r2Serial1" args="1 /dev/ttyUSB1 9600" output="screen" >  <remap from="ucCommand" to="uc1Command" />  <remap from="ucResponse" to="uc1Response" />  </node></launch>

Usage:

$ rosrun r2SerialDriver r2SerialDriver 0 /dev/ttyUSB0 9600

or

$ roslaunch r2SerialDriver r2SerialDriver.launch

try:

$ rostopic pub -r 1 /uc0Command std_msgs/String hello_my_serial$ rostopic echo /uc0Response

You may also need to remap the /dev/ttyUSB* to some name you like cuz you may have several usb-serial devices.
If so, just Ref:重新指派usb转串口模块在linux系统中的设备调用名称(English Version: remap your usb-serial devices' names in Linux )

But Kevin mentioned a question: "Interesting, but a lot of my serial stuff is send a message and receive a response back. Instead of separate publish/subscribes have you tried a service? That seems like it would work nicely for this."

I also noticed a problem: The Linux's System RAM and CPU will be much costed by r2serial_driver when it is running.

Next time, we'll see how to use Kevin's service to play ROS serial communication.

2. Use Service to play ROS-Serial communication

see this blog brother below...

http://blog.csdn.net/sonictl/article/details/51372534