WebbotLib AVR library
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subtract

Subtract a given value from the encoder counter.
This allows us to stop the internal counter from overflowing if the encoder continues to rotate in the same direction. This normally means updating another variable and then subtracting a value from the encoder. See the example below.
Syntax
Encoder. subtract(ticks)
Where Encoder is the name you have given to the device in Project Designer.
Parameters
TypeNameDescription
'ticks'
The number of ticks to reduce the current tick count by.
Returns
None
Note
This will only effect the internal counter and so getTicks() will continue to return the original value until the next time read() is called.
Example
Assumptions:
We start by having a variable called 'distanceCM', which needs to be signed as the wheel can go forward and in reverse. So let's use an 'int32_t'.
Next: every time we have got at least 1000 ticks we will update our variable with 1 more centimetre and reduce the encoder counter by 1000. This means that the remaining value in the encoder will be between -999 and +999 represents the fraction of a centimetre.
So here is the code:-
int32_t distanceCM; // Distance in cm - automatically initialised to 0
 
// This routine is called repeatedly - its your main loop
TICK_CONTROL appControl(LOOP_COUNT loopCount, TICK_COUNT loopStart){
    // Read the encoder and store the value
    myEncoder.read();
 
    // Get the current number of ticks
    TICK_COUNT ticks = myEncoder.getTicks();
 
    // Adjust for any whole cm
    if( ticks >= 1000 ){
        myEncoder.subtract(1000);
        // Update my local variable as well
        ticks -= 1000;
        distanceCM++;
    }else if( ticks <= -1000){
        myEncoder.subtract(-1000);
        // Update my local variable as weill
        ticks += 1000;
        distanceCM--;
    }
    // Print distance travelled to standard out
    double total = ticks;
    total /= 1000;
    total += (double)distanceCM;
    cout << "Distance = " << total << '\n';
}

 

 

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