Chief Delphi - Sonar Function Issue

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Sonar Function Issue

I am using the Maxbotics sensor, obtaining data through the AD, and need to find the difference between two consecutive readings. In the following, I have a distance function that returns the distance to the target in inches, and I use that number in the following function delta_distance() to find the difference between consecutive readings.

The problem is, when I run the thing, my return is always the inverse of the actual distance reading, and the issue is, solved with a printf, that my temp variable is never changing. It remains at zero constantly.

Code:

/*******************************************************************************

* FUNCTION NAME: distance

* PURPOSE:       returns a realtime distance from sonar, in inches

* CALLED FROM:   This file

* ARGUMENTS:     

*     Argument       Type             IO   Description

*     --------       -------------    --   -----------

*    none

* RETURNS:       unsigned int

*******************************************************************************/



unsigned int distance(void)

{



             return (unsigned int) Get_Analog_Value(rc_ana_in01)/s;

}









/*******************************************************************************

* FUNCTION NAME: delta_distance

* PURPOSE:      returns difference in range readings between cycles

* CALLED FROM:   This file

* ARGUMENTS:     

*     Argument       Type             IO   Description

*     --------       -------------    --   -----------

*    none

* RETURNS:       signed int

*******************************************************************************/

int delta_distance(void)

{

    int temp;

    

    temp -= distance();



    return (int) temp;



    temp=distance;

}

As well, if anyone can quickly through up a workable averaging function I'd be much obliged. I've tried without success, typically ending up with a constantly incrementing distance value, or erratic jumping output.

Code:

/*******************************************************************************

* FUNCTION NAME: distance

* PURPOSE:       returns a realtime distance from sonar, in inches

* CALLED FROM:   This file

* ARGUMENTS:     

*     Argument       Type             IO   Description

*     --------       -------------    --   -----------

*    none

* RETURNS:       unsigned int

*******************************************************************************/



unsigned int distance(void)

{

 unsigned int temp;

 i++;

 unsigned int Distance;

 

 temp+= (Get_Analog_Value(rc_ana_in01)/2)



 if (i>=5)

    {

          Distance=temp/i;

          i=0;

          

    }         





             return (unsigned int)Distance;

}

Thanks!

Re: Sonar Function Issue

Quote:

Originally Posted by Andrew Blair (Post 581993)

As well, if anyone can quickly through up a workable averaging function I'd be much obliged.

Team 95 has a huge number of IR sensors (BigHAIR: Big Honkin Array of IR sensors), and we keep time history and a running average on them. Here's a snippet

Code:

long IR_range[6]; // current ranges, generated by another function

long IR_range_history[6][4];  // Last 4 readings, not necessarily in order (see below)

long IR_range_average[6]; // running average of last 4 readings



void Average_IR(void) {

   static counter=0;  



   index=counter++%4;  // Keeps from having to copy old data, just

                                 // overwrite one column at a time



   for (i=0;i<6;i++) {

        IR_range_history[i][index]=IR_range[i];

        IR_range_average[i]=0;

        for (j=0;j<4;j++) {

           IR_range_average[i]+=IR_range_history[i][j];

        }

        IR_range_average[i]/=4;

   }

}

Re: Sonar Function Issue

Quote:

Originally Posted by Andrew Blair (Post 581993)

...my temp variable is never changing...

Code:

int delta_distance(void)

{

    int temp;

    

    temp -= distance();



    return (int) temp;



    temp=distance;

}

The temp variable in your code evaporates as soon as delta_distance() returns. If you want to keep a local variable's value between calls to a function, you need to declare it static:

Code:

int delta_distance(void)

{

    static int last_distance = 0; // set to zero only on program start, retains value between function calls

    int delta; 

    delta = distance()-last_distance; // compute difference between distances

    last_distance = distance(); // remember this distance for next time

    return delta;

}