Thanks for the attention, I need a little help.
The problem is the following, I managed to communicate with my Arduino by rosserial. The thing is that it works, it receives the message that is the PWM frequency for the stepper motors. However, I have a very bad delay. How do I make a Real Time System. Something really fast. My application is controls and it is critical to the reaction be extremely fast.
I am using a library called PWM frequency library . This is the code I am using on my arduino:
#include <Wire.h>
#include <ros.h>
#include <geometry_msgs/Twist.h>
#include <std_msgs/Int32.h>
#include <PWM.h> //PWM library for controlling the steppers
//#include <inttypes.h> //not sure about this for the int32_t
ros::NodeHandle nh;
std_msgs::Int32 str_msg;
ros::Publisher chatter("debug", &str_msg);
//Motor pins
//use pin 11 on the Mega instead, otherwise there is a frequency cap at 31 Hz
const int step_pin1 = 11; // the pin that define the steps
const int dir_pin1 = 22; // the dir pin
const int step_pin2 = 12; // the pin that define the steps
const int dir_pin2 = 24;
int32_t frequency1 = 0; //frequency (in Hz)
int32_t frequency2 = 0; //frequency (in Hz)
int32_t duty1 = 0;
int32_t duty2 = 0;
bool dir1 = true;
bool dir2 = true;
void driveCallback ( const geometry_msgs::Twist& twistMsg ){
//need to pubish straigth the motor commands and do the dir calculations on the Arduino
frequency1 = abs( twistMsg.linear.x ) ;//work as motor1_cmd_callback ---- twistMsg.linear.x must already be converted to int32_t
frequency2 = abs( twistMsg.linear.y ) ;//work as motor2_cmd_callback ---- twistMsg.linear.y must already be converted to int32_t
SetPinFrequency(step_pin1, frequency1); //change for the callback function of motor1_cmd
SetPinFrequency(step_pin2, frequency2); //change for the callback function of motor2_cmd
str_msg.data = frequency1;
chatter.publish(&str_msg);
if(frequency1 > 0){
duty1 = 32768;
if(twistMsg.linear.x >= 0){
digitalWrite(dir_pin1, HIGH);
}
else{
digitalWrite(dir_pin1, LOW);
}
}
else{
duty1 = 0;
}
if(frequency2 > 0){
duty2 = 32768;
if(twistMsg.linear.y >= 0){
digitalWrite(dir_pin2, HIGH);
}
else{
digitalWrite(dir_pin2, LOW);
}
}
else{
duty2 = 0;
}
}
ros::Subscriber<geometry_msgs::Twist> driveSubscriber("comm_drive_robot", &driveCallback) ;
void setup(){
//initialize all timers except for 0, to save time keeping functions
InitTimersSafe();
nh.initNode();
// Subscribe to the steering and throttle messages
nh.subscribe(driveSubscriber);
nh.advertise(chatter);
// =======================================================================================
/* ================ PWM Function ======================================================= */
//PWM + direction to the motors 1
pinMode(step_pin1, OUTPUT);
pinMode(dir_pin1, OUTPUT);
//PWM + direction to the motors 2
pinMode(step_pin2, OUTPUT);
pinMode(dir_pin2, OUTPUT);
}
void loop(){
nh.spinOnce();
pwmWriteHR(step_pin1, duty1);
pwmWriteHR(step_pin2, duty2);
delay(1);
}
Originally posted by renanmb on ROS Answers with karma: 33 on 2017-08-03
Post score: 0
Original comments
Comment by gvdhoorn on 2017-08-03:\
if(twistMsg.linear.x >= 0)
I'm not sure, but geometry_msgs/Twist uses floats/doubles for all its fields. The chance that those are != 0 is rather high, so I don't think this is a good way to do what you want.
And I'm not an expert, but in most cases, the idea is to ..
Comment by gvdhoorn on 2017-08-03:
.. compute a PWM duty cycle based on the ratio max/commanded vel. In the case where you have DIR pins, you'll also need to update those (probably based on the sign of the incoming Twist).
But this all depends on whether your motors / controller actually support this mode of operation.