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
{

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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

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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

chokings · January 24, 2022, 1:30am

Thank you for answer.

A problem occurs when downloading and building the firmware code. I wrote a question about it. How can I solve this?

Thank you again.

pkowalsk · January 24, 2022, 10:15am

Hi Chokings,
You can find an answer there that will help you solve the problem with building PIO project.
Please, let me know if it helped you.

Best regards,
Paweł