Auton Programming Help

VEX V5 General Discussion Technical Discussion
#1

Hi, I was working on our teams autonomous code and was wanting to make a function for our holonomic drive to refer to either driving forward backward or strafe. An example to referring to this is " drive(f);" This would make it drive forward and similar for backwards. I was just wondering how you would determine that “f” in your function means forward.

I am basically asking in your function how to show that “drive(f)” means go forward, “drive(b)” goes backwards, “drive(l)” strafes left, and how “drive®” strafes right.

My drive cortex ports are
Front Left: 2
Front Right: 3
Back Left: 4
Back Right; 5

Just for reference my function is currently set up similar to:

void drive(){
//requested help would go in here
}

#2

It’s a bit harder to do that in the holonomic driving because you need to tell the motors both the drive and rotation at the same time.

Normally you have “motor[one_of_them] = +X + Y + Rotation” kind of notation. Hard to go back and put the rotate in later. Not impossible, just not very clean.

Taken from Cody’s tutorial

driveX() and driveY() and rotate() were ones I have seen in autonomous where it returned the X Y and rotate values back to the drive controlling function. Those functions each had their own PID for the dimension of movement. But take care as rotate with drive gets tricky.

#3

Note that I got ALL the signs wrong in that picture because I guessed which way the motor spins wrong.

You may find some of this code interesting.

#4

So i’m not exactly sure what you’re saying. what I was going to do was something similar to this sudo code…

(f) {
motor(FL) = 127;
motor(FR) = -127;
motor(BL) = -127;
motor(BR) = 127;
}
Here I’m trying to make a “sub-function” inside my drive function that would make the program go forward, although I don’t know the syntax on how to assign this series of commands to a variable.
Then to reference it I was wanting to be able to do something similar to this…

task main(){
while(true)
{
drive(f);
}
}

I would do this inside the drive function for all my directions Ex: Forward, Backward, and Strafe.

I just don’t know how to make it reference the “sub-function” or whatever you might call it.

#5

Oh ok I get it, that methodology will work but you’ll have drifting issues.

You want something like so…

// Pseudocode
forward(int time) {

	motor(FL) = 127;
	motor(FR) = -127;
	motor(BL) = -127;
	motor(BR) = 127;

	wait(time);

	stopAllMotors();

}

task autonomous(){

	forward(100);
	turn();
	forward(250);
	score();

	# Loop endlessly here so the autonomous task doesn't stop prematurely
	while(true) {
		wait(1)
	}
}

It’s WAYYYY better to use encoder values instead of time as the battery voltage and other factors will make the robot drive different amounts forward each time.

#6

That is more correct, although I wanted to keep all my drive “functions” in one function. so for example…

void drive(){
forward{ //drive forward full speed
motor(FL) = 127;
motor(FR) = -127;
motor(BL) = -127;
motor(BR) = 127;
}
backward{ //drive backward full speed
motor(FL) = -127;
motor(FR) = 127;
motor(BL) = 127;
motor(BR) = -127;
}
strafe_left{ //strafe left full speed
motor(FL) = -127;
motor(FR) = -127;
motor(BL) = -127;
motor(BR) = -127;
}
strafe_right{ //strafe right full speed
motor(FL) = 127;
motor(FR) = 127;
motor(BL) = 127;
motor(BR) = 127;
}
}
void stop(){
motor(port1-10) = 0; //NOTE: This is just to reference that all motors are stopped, in actuality
} // it would have to be written out 10 times, one for each motor.

Then I could reference it in my auton as shown below…

task autonomous(){
drive(f); //drive forwards for .5 sec
wait1msec(500);
stop(); //stop all motors
drive(sl); //strafe left for .5 sec
wait1msec(500);
stop(); //stop all motors
drive(b); //drive backwards for .5 sec
wait1msec(500);
stop(); //stop all motors
drive(sr); //strafe right for .5 sec
wait1msec(500);
stop(); //stop all motors
}

I want my end result to be something like this so that I only have to use a parameter within my drive function to specify whether or not I’m going forward, backward, strafe left, or strafe right.

P.S. I was planning on using encoders after I got this tidbit of code to work.

#7

I would not recommend using ‘f’, b’, etc. as parameters for an autonomous function call. However, if you really want to, you can do this:


void drive(char dir) {
  switch dir {
    case 'f': //If argument is 'f', drive Forward
      motor[flDrive] = 
        motor[frDrive] =
        motor[blDrive] =
        motor[brDrive] =
       127;
    break;
    case 'b': //If argument is 'b', drive Backward
      motor[flDrive] =
        motor[frDrive] =
        motor[blDrive] =
        motor[brDrive] =
        -127;
    break;
    case 'l': //If argument is 'l', strafe Left
      motor[flDrive] =
        motor[brDrive] =
        -127;
      motor[frDrive] =
        motor[blDrive] =
        127;
    break;
    case 'r': //If argument is 'r', strafe Right
      motor[flDrive] =
        motor[brDrive] =
        127;
      motor[frDrive] =
        motor[blDrive] =
        -127;
    break;
    case default: //If the char passed in is not f, l, r, or b, stop motors
      motor[flDrive] = 0;
      motor[frDrive] = 0;
      motor[blDrive] = 0;
      motor[brDrive] = 0;
    break;
  }
}

Also, you need to include single quotation marks (’ ') around the argument when you call the function. This tells the program that it’s a char rather than a variable name. That looks like this:


drive('f');
#8

Thank you soooo much!!! This is exactly what i was looking for in how to write my auton code. I will let you know how it works after I implement it into my code.

Thanks!

#9