5 replies to this topic

[capn]

Hey everyone!

I am very new to micro-processors and programming in general, but I am pretty good with discrete electronics but I am by no means an expert.

I want to start some threads that will help very base level beginners like myself understand some basic concepts.

My question for today is, how do I compare bits for say, direction control of motors?

I understand that if I had an analog input (0-3.3V) it gets converted to a 10 bit integer, 0-1023, assuming that I haven't changed the range.

Can you more experienced people help me fill in my pseudo code?

public static void Main()
{
InputPort Xaxis = new InputPort(pins.analogPinA1);       // Defining the analog input port as my joystick axis 
OutputPort Direction1 = new OutputPort(pins.outputpin1); // Defining the output port to a motor driver direction 1 enable
OutputPort Direction2 = new OutputPort(pins.outputpin2); // Defining the output port to a motor driver direction 2 enable

//I have made the range for directions 0-1023, with a 128bit "dead zone"

For(Xaxis > 576bits)
   {
   Direction1.value = true;               //this gives me direction forward
   }

For(Xaxis < 448bits)
   {
   Direction2.value = true;                //this gives me direction reverse
   }

}

[Chris Walker]

Hi capn,

[Quick note: you'll want to say "Xaxis > value of 576" and "Xaxis < value of 448" (i.e. value rather than bits). I totally know what you mean, but a lot of people will get confused or might ignore your post due to the accidental misnaming. Odd but true.]

For Xaxis, instead of creating an InputPort you'll want to create an AnalogInput. And actually, I'd do something like:

AnalogInput xAxisInput = new AnalogInput(Pins.GPIO_PIN_A1);
int xAxisValue= xAxisInput.Read();

if (xAxisValue > 576)
{
    Direction1.Value = true;
}
else if (xAxisValue <448)
{
    Direction2.Value = true;
}

[capn]

Thanks Chris! I know I wasn't right with the nomenclature, I just wanted to make the code decipherable.

This might be a rudimentary question, but why use an "IF" statement instead of a "FOR" loop?

Also would it be more right to have the direction outputs as:

if (xAxisValue > 576)
            {
                Direction1.Write(true);     //gives the motor 1 direction 1 a true reading, this is forward
            }
            else if(xAxisValue < 448)
            {
                Direction2.Write(true);     //gives the motor 1 direction 2 a true reading, this is reverse
            }

[Chris Walker]

This might be a rudimentary question, but why use an "IF" statement instead of a "FOR" loop?

A for loop executes a section of code one or more times (depending on the parameters that you give to 'for'). An if block executes only if something is/is not true. In this case, you'll probably want to read the value over and over again--either on a timer or in an infinite loop ("while(true)"). There are a lot of good C# primers out there which describe the various operations like for and if...would it bef halpful if we found a good one to recomend to you?

Also would it be more right to have the direction outputs as:

if (xAxisValue > 576)
{
    Direction1.Write(true);     //gives the motor 1 direction 1 a true reading, this is forward
}
else if(xAxisValue < 448)
{
    Direction2.Write(true);     //gives the motor 1 direction 2 a true reading, this is reverse
}

Yes, actually the code I wrote above (Direction1.Value) isn't correct. Sorry about that! But if you have two motors controlling "forward" and "back", you'll want to go one step further--turn _off_ the one you're not using! Otherwise they'll both try to run.

if (xAxisValue > 576)
{
    Direction1.Write(true);     //gives the motor 1 direction 1 a true reading, this is forward
    Direction2.Write(false);
}
else if(xAxisValue < 448)
{
    Direction2.Write(true);     //gives the motor 1 direction 2 a true reading, this is reverse
    Direction1.Write(false);
}

Also, if I might make a recommendation: rename Direction1 and Direction2 to something like "forwardMotorOutput" and "reverseMotorOutput"... It'll make the code easier to understand and maintain.

Chris

[capn]

A for loop executes a section of code one or more times (depending on the parameters that you give to 'for'). An if block executes only if something is/is not true. In this case, you'll probably want to read the value over and over again--either on a timer or in an infinite loop ("while(true)"). There are a lot of good C# primers out there which describe the various operations like for and if...would it bef halpful if we found a good one to recomend to you?

Of course! I am always looking for more information. And yes, I will want to read this value over and over again, that's why I had initially put the code within a for loop.

Yes, actually the code I wrote above (Direction1.Value) isn't correct. Sorry about that! But if you have two motors controlling "forward" and "back", you'll want to go one step further--turn _off_ the one you're not using! Otherwise they'll both try to run.

if (xAxisValue > 576)
{
    Direction1.Write(true);     //gives the motor 1 direction 1 a true reading, this is forward
    Direction2.Write(false);
}
else if(xAxisValue < 448)
{
    Direction2.Write(true);     //gives the motor 1 direction 2 a true reading, this is reverse
    Direction1.Write(false);
}

Also, if I might make a recommendation: rename Direction1 and Direction2 to something like "forwardMotorOutput" and "reverseMotorOutput"... It'll make the code easier to understand and maintain.

Chris

In this example I am only controlling one motor which has the possibility to run in forward or reverse. And in my realm of hardware, I need two outputs for each motor as each motor will have its own respective H-bridge; like so:



So for my robot, it would essentially have an If...ElseIf statement for each motor?

[Chris Walker]

So for my robot, it would essentially have an If...ElseIf statement for each motor?

I believe so. If motor control is all you're doing, you can put it all in one big "while(true)" loop.

while(true)
{
    // process analog input for motor 1
    [code goes here]

    // process analog input for motor 2
    [code goes here]
}