I am trying to connect a VOC sensor in ROS via RS485 communication port.
I opened the port with serial package downloaded form wjwwood.com now.
Then I defined a char array request[8]={0x01,0x03,0x00,0x00,0x00,0x02,0xc4,0x0b} and sent it to the port by the code ser.write(request).As a result, I received an response frame ("01 83 03 01 31") which means my request frame was wrong in Modbus protocol.
Is it right to send a char array to the port?How to send hex type data to the serial port?
Sorry for my poor English.
Here are my codes.
#include <string>
#include <iostream>
#include <cstdio>
// OS Specific sleep
#ifdef _WIN32
#include <windows.h>
#else
#include <unistd.h>
#endif
#include "serial/serial.h"
using std::string;
using std::exception;
using std::cout;
using std::cerr;
using std::endl;
using std::vector;
void my_sleep(unsigned long milliseconds) {
#ifdef _WIN32
Sleep(milliseconds); // 100 ms
#else
usleep(milliseconds*1000); // 100 ms
#endif
}
void enumerate_ports()
{
vector<serial::PortInfo> devices_found = serial::list_ports();
vector<serial::PortInfo>::iterator iter = devices_found.begin();
while( iter != devices_found.end() )
{
serial::PortInfo device = *iter++;
printf( "(%s, %s, %s)\n", device.port.c_str(), device.description.c_str(),
device.hardware_id.c_str() );
}
}
void print_usage()
{
cerr << "Usage: test_serial {-e|<serial port address>} ";
cerr << "<baudrate> [test string]" << endl;
}
int run(int argc, char **argv)
{
if(argc < 2) {
print_usage();
return 0;
}
// Argument 1 is the serial port or enumerate flag
string port(argv[1]);
if( port == "-e" ) {
enumerate_ports();
return 0;
}
else if( argc < 3 ) {
print_usage();
return 1;
}
// Argument 2 is the baudrate
unsigned long baud = 0;
#if defined(WIN32) && !defined(__MINGW32__)
sscanf_s(argv[2], "%lu", &baud);
#else
sscanf(argv[2], "%lu", &baud);
#endif
// port, baudrate, timeout in milliseconds
serial::Serial my_serial(port, baud, serial::Timeout::simpleTimeout(1000));
cout << "Is the serial port open?";
if(my_serial.isOpen())
cout << " Yes." << endl;
else
cout << " No." << endl;
// Get the Test string
char ask[8]={0x01,0x03,0x00,0x00,0x00,0x02,0xc4,0x0b};
int count = 0;
int i=0;
string test_string;
if (argc == 4) {
test_string = ask;
} else {
test_string = ask;
}
// Test the timeout, there should be 1 second between prints
cout << "Timeout == 1000ms, asking for 1 more byte than written." << endl;
while (count < 10) {
size_t bytes_wrote = my_serial.write(test_string);
string result = my_serial.read(test_string.length()+1);
cout << "Iteration: " << count << ", Bytes written: ";
cout << bytes_wrote << ", Bytes read: "<<endl;
cout << result.length() << ", String read: " << result << endl;
//for( i=0;i<8;i++) {printf("%x\n",result[i]);}
count += 1;
}
return 0;
}
int main(int argc, char **argv) {
try {
return run(argc, argv);
} catch (exception &e) {
cerr << "Unhandled Exception: " << e.what() << endl;
}
}
And here are the results I received.
luc@luc-ThinkPad-T450:~/catkin_ws$ rosrun serial serial_example /dev/ttyUSB0 11
Is the serial port open? Yes.
Timeout == 1000ms, asking for 1 more byte than written.
Iteration: 0, Bytes written: 2, Bytes read:
3, String read: �
Iteration: 1, Bytes written: 2, Bytes read:
3, String read: 1
Iteration: 2, Bytes written: 2, Bytes read:
3, String read: �1
Iteration: 3, Bytes written: 2, Bytes read:
3, String read: `
Iteration: 4, Bytes written: 2, Bytes read:
3, String read: ��
Iteration: 5, Bytes written: 2, Bytes read:
3, String read: 1
Iteration: 6, Bytes written: 2, Bytes read:
3, String read: �
Iteration: 7, Bytes written: 2, Bytes read:
3, String read: 1
Iteration: 8, Bytes written: 2, Bytes read:
3, String read: �(�
Iteration: 9, Bytes written: 2, Bytes read:
3, String read:
There are some unreadable codes like �(�, but I don't know why.
Originally posted by LucYang on ROS Answers with karma: 56 on 2017-10-09
Post score: 0
Original comments
Comment by jayess on 2017-10-09:
Should the link be http://wjwwood.io instead of http://wjwwood.com?