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Revision 399f7d1b

ID399f7d1bbc8102e5b1859f12ce0a1ec7daeb821d

Added by Thomas Mullins over 11 years ago

Changed sonar/bom timer to 64 prescalar

Also fixed bug in the bom's timer usage, where it depended on an integer
overflow that was no longer occuring due to the higher F_CPU.

View differences:

scout_avr/src/bom.cpp
152 152 
  if (is_rising) {
153 153 
    // TODO check 320us? or have 320us timeout on rising edge?
154 154 
  } else {
155 
    // uses timer 5, assuming prescale 1/8
155 
    // uses timer 5, assuming prescale 1/64
156 156 
    // timer 5 is set up by range_init()
157 
    // this should be in units of microseconds
158 
    int now = TCNT5 / (F_CPU / 8 / 1000000);
157 
    int now = TCNT5;
158 
    int min_low = TIME_MICROS(MIN_LOW_PW, 64);
159 
    int max_low = TIME_MICROS(MAX_LOW_PW, 64);
160 
    int min_high = TIME_MICROS(MIN_HIGH_PW, 64);
161 
    int max_high = TIME_MICROS(MAX_HIGH_PW, 64);
159 162
160 163 
    if (rx->count) {
161 
      int diff = now - rx->last_time;
164 
      int diff = (now - rx->last_time);
162 165 
      rx->bits <<= 1;
163 
      if (MIN_LOW_PW < diff && diff < MAX_LOW_PW) {
166 
      if (min_low < diff && diff < max_low) {
164 167 
        // 0 already in bits
165 
      } else if (MIN_HIGH_PW < diff && diff < MAX_HIGH_PW) {
168 
      } else if (min_high < diff && diff < max_high) {
166 169 
        // add 1 to bits
167 170 
        rx->bits |= 1;
168 171 
      } else {
scout_avr/src/bom.h
5 5 
#include <stdint.h>
6 6 
}
7 7 

  		




  
  8
  
    
//#include <bom/bom.h>


  		




  
  9
  
    

  		




  8
  10
  
    
// constants for direction


  		




  9
  
  
    
#define BOM_FRONT 0


  		




  10
  
  
    
#define BOM_BACK  1


  		




  11
  
  
    
#define BOM_LEFT  2


  		




  12
  
  
    
#define BOM_RIGHT 3


  		




  
  11
  
    
#define BOM_FRONT 0 //(bom::bom::FRONT)


  		




  
  12
  
    
#define BOM_BACK  1 //(bom::bom::BACK)


  		




  
  13
  
    
#define BOM_LEFT  2 //(bom::bom::LEFT)


  		




  
  14
  
    
#define BOM_RIGHT 3 //(bom::bom::RIGHT)


  		




  13
  15
  
    

  		




  14
  16
  
    
// timing, in us, for read of valid bits


  		




  15
  17
  
    
#define MIN_LOW_PW 600


  		












  

    
      scout_avr/src/range.cpp
    
  





  12
  12
  
    
 * 


  		




  13
  13
  
    
 * 37.5ms * 8 MHz / 8 prescaler = 37500 max wait


  		




  14
  14
  
    
 * 37.5ms * 16 MHz / 8 prescaler = problem


  		




  
  15
  
    
 * 37.5ms * 16 MHz / 64 prescaler = 9375 max wait


  		




  15
  16
  
    
 */


  		




  16
  17
  
    

  		




  17
  18
  
    
struct range_t {


  		




  ......




  64
  65
  
    
  // enable INT2 and INT3


  		




  65
  66
  
    
  EIMSK |= _BV(INT2) | _BV(INT3);


  		




  66
  67
  
    
  


  		




  67
  
  
    
  // CS1 = 2, 1/8 prescaler


  		




  
  68
  
    
  // CS1 = 3, 1/64 prescaler


  		




  68
  69
  
    
  // if this is changed, remember to change recv_edge in bom.cpp!


  		




  69
  
  
    
  TCCR5B = _BV(CS51);


  		




  
  70
  
    
  TCCR5B = _BV(CS50) | _BV(CS51);


  		




  70
  71
  
    

  		




  71
  72
  
    
  // set tx as output


  		




  72
  73
  
    
  DDRG |= _BV(DDG1);


  		












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