I want to make _pwm a rostopic

chokings · January 13, 2022, 7:14am

Hi!

I am a student studying ros using rosbot 2.0.

I want to make _pwm rostopic to check the control input of the motor.

Looking at the firmware code, I checked that the function getDutyCycle in the motor driver (DRV8848.h and DRV8848.cpp) can read the PWM as _pwm.read().

github.com

byq77/drv88xx-driver-mbed/blob/61854e885cff79ea9113e0ecef8e32a727477fcb/DRV8848.h

#ifndef __DRV884_H__
#define __DRV884_H__

#include <mbed.h>
#include "DCMotor.h"

typedef struct DRV8848_Params
{
    PinName ain1;
    PinName ain2;
    PinName pwm1;
    PinName bin1;
    PinName bin2;
    PinName pwm2;
    PinName nfault;
    PinName nsleep;
} DRV8848_Params_t;

class DRV8848
{

This file has been truncated. show original

Should I add getDutyCycle to main.cpp in firmware?

github.com

husarion/rosbot-stm32-firmware/blob/main/src/main.cpp

/** @file main.cpp
 * ROSbot firmware.
 * 
 * @author Husarion
 * @copyright MIT
 */
#include <rosbot_kinematics.h>
#include <rosbot_sensors.h>
#include <ImuDriver.h>
#include <ros.h>
#include <sensor_msgs/JointState.h>
#include <geometry_msgs/Twist.h>
#include <geometry_msgs/PoseStamped.h>
#include <std_msgs/UInt32.h>
#include <sensor_msgs/Imu.h>
// #include <rosbot_ekf/Imu.h>

#ifndef ROS_NOETIC_MSGS
#   define ROS_NOETIC_MSGS 0
#endif

This file has been truncated. show original

Or should I write the code by adding a new node to the rosbot_ekf package?

I would really appreciate it if you could give me a starting point and some details.

Thanks for reading.

pkowalsk · January 21, 2022, 3:08pm

Hi Chokings,
You can use the RosbotDrive::getSpeed function that is defined in the RosbotDrive.cpp file. It is based on getDutyCycle() function.

I have prepared for you an outline of the solution that is in my fork (link to commit). When you subscribe /pwm topic, message data (Float32) tells you the ratio of low state time to cycle period.

I hope this solution suits you.

Best regards,
Paweł