How do I Link a (group of) Joystick button(s) to a motor?

Technical C/C++
1

OK, I’m not new at the programming thing but I seem to be having one of those problems that I believe should have a simple solution. Long story short, our robot has a roller on the front. I want buttons 4, 3, and 5 on the Joystick attached to USB port 3 on the DS to control Reverse, Stop, and Forward respectively. I’m extending the IterativeRobot Class for this code. This is what I have so far:


// These lines are in the declaration
Joystick* m_rollerStick;        // joystick 3 (roller)
Victor *m_roller;
int m_rollerCondition;

// These lines are in the constructor
m_roller = new Victor(4,3);
m_rollerStick = new Joystick(3);
m_rollerCondition = 0;

//These lines are in TelopPeriodic()
.
.
.
if (m_ds->GetPacketNumber() != m_priorPacketNumber) {
.
.
.
// Roller Control
if(m_rollerStick->GetRawButton(4)) m_rollerCondition = -1;
if(m_rollerStick->GetRawButton(5)) m_rollerCondition = 1;
if(m_rollerStick->GetRawButton(3)) m_rollerCondition = 0;

switch (m_rollerCondition)
    {
        case -1:
            m_roller->Set(-1);
            break;
        case 1:
                m_roller->Set(1);
                break;
        case 0:
            default:
                m_roller->Set(0);
                break;
    }
.
.
.
}

I think that I’ve pasted all of the pertinent code here so I don’t have to copy & paste (or upload) the entire file here.

By the way, I’ve also tried using the Joystick::GetY() function to just output the Y axis on the Joystick directly to the Victor::Set() like this


m_roller->Set(m_rollerStick->GetY());

However that just caused our roller to run at a forward speed just outside of the deadband. Also, I’m pretty sure that this is a programming issue since Im able to use the m_roller->Set() and m_roller->SetRaw() functions to run the roller.

Thank you all for any help that you can provide for me.

2

I can’t see anything wrong with the code you posted. I’m not sure that you are reading the stick, however.

Print out the status of “m_rollerStick->GetRawButton(X)” and make sure you are correctly reading the buttons. This will also indicate whether for some reason the block of code isn’t getting run because of a conditional somewhere.

Lastly, make sure you don’t re-set “m_roller” later in the code.

3

I think I see the problem with your code. Basically, it won’t hold the value the victor is set at.

It works this way: Say you push button 4. One cycle reads the button:

if(m_rollerStick->GetRawButton(4)) m_rollerCondition = -1;

and since it sees that button 4 is pushed, it sets the victor to -1. Then it cycles through again. But since you’re not holding down the button, it won’t keep the victor at -1. Instead, it will do your default action:

default:
m_roller->Set(0);
break;

which sets the victor back to 0. So what you should do is set up some code that reads a button state, sets a variable that stays at that value until it detects that a different button is pushed. I’ll leave the implementation of that to the reader =]

Let me know if that wasn’t clear enough. I’m good at explaining things to myself; it’s explaining things to others that’s hard =]