www.micro-examples.com : PicoDetector

*******************************************************************************
* picoDetector : an ultra simple and cheap metal detector
*******************************************************************************
*
* Author : Bruno Gavand, april 2009
* see more details on http://www.micro-examples.com/
*
* source code for mikroC PRO compiler V1.65
* feel free to use this code at your own risks
*
* target : PIC12, oscillator in HS mode, watchdog enabled
*
* PIC PIN Assignemnt :
*
* GP0 : detect LED indicator
* GP1 : calibrate LED indicator
* GP2 : NC
* GP3 : NC
* GP4, GP5 : inductor
*
*******************************************************************************
*/

1. define MAXTRY 15 // number of watchdog restart to calibrate loop counter

unsigned char ctr ; // number of loops between two watchdog resets unsigned char previous ; // previous value of ctr unsigned char calibr ; // calibration value when oscillator runs free unsigned char restarts ; // number of watchdog restarts unsigned char en ; // enable flag, allows detection

/*

* main loop
*/

void main()

       {
       unsigned char   i ;
       

       /*
        * configure GPIO as digital port
        */
       CMCON0 = 7 ;
       ANSEL = 0 ;
       TRISIO = 0 ;
       GPIO = 0 ;

       /*
        * power up ?
        */
       if(STATUS.NOT_TO)
               {
               /*
                * yes, init variables
                */
               restarts = 0 ;
               calibr = 1 ;
               }

       /*
        * watchdog reset counter
        */
       if(restarts < 255) restarts++ ;

       /*
        * if counter differs too much from calibration value
        */
       if((previous ^ ctr) > calibr)
               {
               /*
                * turn detect LED on
                */
               GPIO.F0 = en ;
               
               /*
                * if not on power up
                */
               if(STATUS.NOT_TO == 0)
                       {
                       /*
                        * while in calibration mode
                        */
                       if(restarts < MAXTRY)
                               {
                               /*
                                * shift calibration value
                                * and wait a little bit
                                */
                               calibr <<= 1 ;
                               Delay_ms(5) ;
                               }
                       }
               else
                       {
                       /*
                        * turn detect LED off
                        */
                       GPIO.F0 = 0 ;
                       }
               }

       /*
        * save last counter
        */
       previous = ctr ;

       /*
        * is calibration over ?
        */
       if(restarts > MAXTRY)
               {
               /*
                * yes, turn calibrate LED off
                * and set enable flag
                */
               GPIO.F1 = 0 ;
               en = 1 ;
               }
       else
               {
               /*
                * no, turn calibrate LED on
                * and clear enable flag
                */
               GPIO.F1 = 1 ;
               en = 0 ;
               }

       /*
        * set watchdog prescaler
        */
       OPTION_REG = 0b11111001 ;
       
       /*
        * start counter, to be interrupted by watchdog
        */
       ctr = 0 ;
       for(;;)
              {
              ctr++ ;
              }
       }