RC Car Officially Hacked? (Not quite)

Alright, so I'm close to being able to drive my RC car around. I'm able to do a little controlling at my desk. (I have to fix some stuff with the way my xbox controller's interface mapping.)

I'm gonna walk through some of the stuff I did to do this since my last post.

I first hooked up my motors to my power banks to see if I could get them to drive. Apologies for the vertical video, dunno what I was thinking....

So after that  I had to get everything all wired up to the Arduino. I think the shield's perf board section ended up being really helpful, and I had to do a lot of jank wiring to get everything set up properly. It's an absolute rat's nest, but it works.

I also cut apart a USB A to A cable to connect to my old USB powerbanks. Unfortunately, I didn't realize the current draw for the motors was more than what the USB powerbank could handle, and they shut off because of presumably some safety feature for like a short or something. I was however able to use 2 in parallel, and it seems to work fine.

So my final set up is pictured below.

With the hardware in place, I needed to get my code in place.

Being as lazy as I am, I looked at a motor driver library I had used back in grad school and used it for a test program I wrote:

/*
	Motor test program excersizes 3 motors on the motor driver
	*/
	#include "motor_controller.h"
	#define M1_IN1 2
	#define M1_IN2 4
	#define M1_ENA 3
	#define M2_IN1 5
	#define M2_IN2 7
	#define M2_ENA 6
	#define MAX_VEL 255
	#define VEL_STEP 5
	#define NUM_STEP (255/5)
	MotorController motorController1(M1_IN1, M1_IN2, M1_ENA);
	MotorController motorController2(M2_IN1, M2_IN2, M2_ENA);
	// the setup routine runs once when you press reset:
	void setup() {
	}
	// the loop routine runs over and over again forever:
	void loop() {
	static int velocity = -MAX_VEL;
	static int dir = 1;
	if (velocity > 255) {
	dir = -1;
	}
	if (velocity < -255)
	{
	dir = 1;
	}
	motorController1.turnMotor(velocity);
	motorController2.turnMotor(velocity);
	velocity += 5*dir;
	delay(200);
	}

This program basically just cycled through some different values being sent to the motors via PWM.

I was able to see that varying the turning motor speed didn't really yield any intermediate turning angles. It's still a very ternary steering system, either straight right or left. I also realized that for many of the values being sent through, there's a large "dead band" where the motors don't even move. That aside I knew then, I could hook this up to ROS!

Writing very little code, I whipped this up:

/*
	* rosserial Subscriber Example
	* Blinks an LED on callback
	*/
	#include <ros.h>
	#include <geometry_msgs/Twist.h>
	#include "motor_controller.h"
	#define M1_IN1 2
	#define M1_IN2 4
	#define M1_ENA 3
	#define M2_IN1 5
	#define M2_IN2 7
	#define M2_ENA 6
	MotorController motorController1(M1_IN1, M1_IN2, M1_ENA);
	MotorController motorController2(M2_IN1, M2_IN2, M2_ENA);
	ros::NodeHandle nh;
	void messageCb( const geometry_msgs::Twist& twist_msg){
	long x_lin_vel = map(twist_msg.linear.x*100, -50, 50, -255, 255);
	long z_ang_vel = map(twist_msg.angular.z*100, -50, 50, -255, 255);
	motorController1.turnMotor(x_lin_vel);
	motorController2.turnMotor(z_ang_vel);
	}
	ros::Subscriber<geometry_msgs::Twist> sub("cmd_vel", &messageCb );
	void setup()
	{
	nh.initNode();
	nh.subscribe(sub);
	}
	void loop()
	{
	nh.spinOnce();
	delay(1);
	}

Basically it can use the twist message that I tested in the turtle sim post I made a while back and directly use it on the Arduino. One of the main problems is that I can at the same time have max steering and max velocity. This means I can't turn currently, and I'll need to fix that. I think likely the next update I make will feature an updated controller mapping so I can actually drive this car around. You can see the current state of things here:

PS

I've also worked a bit more of my cover EP stuff, and I've gotten distracted and want to cover more songs... It's so hard sometimes because there's so many songs out there that I feel like I'd like to cover. Anyway, I want to hopefully get to recording before September.