adc.c

   1 #include <avr/io.h>
   2 #include <avr/interrupt.h>
   3
   4 #include "lights.h"
   5
   6 static unsigned char adc_mux[] = { // pwmleds should be first
   7         // 0: pwmled 0: 1.1V, ADC3 (PA4), single-ended
   8         _BV(REFS1) | _BV(MUX1) | _BV(MUX0),
   9         // 1: pwmled 1: 1.1V, ADC0,1 (PA0,1), gain 1 or 8
  10         _BV(REFS1) | _BV(MUX3) | _BV(MUX2),
  11         // 2: pwmled 2: 1.1V, ADC2,1 (PA2,1), gain 1 or 8
  12         _BV(REFS1) | _BV(MUX3) | _BV(MUX2) | _BV(MUX1) | _BV(MUX0),
  13         // 3: ambient light: 1.1V, ADC4 (PA5), single-ended
  14         _BV(REFS1) | _BV(MUX2),
  15         // 4: batt voltage: 1.1V, ADC5 (PA6), single-ended
  16         _BV(REFS1) | _BV(MUX2) | _BV(MUX0),
  17 };
  18
  19 #define AMBIENT_ADC N_PWMLEDS
  20
  21 #define LAST_ADC (sizeof(adc_mux)/sizeof(adc_mux[0]))
  22 volatile static unsigned char current_adc;
  23 static unsigned char adc_ignore;
  24
  25 static void start_next_adc()
  26 {
  27         while (current_adc > 0) {
  28                 --current_adc;
  29
  30                 // test if current_adc should be measured
  31                 if (current_adc < N_PWMLEDS && pwmled_needs_adc(current_adc))
  32                         goto found;
  33                 if (current_adc == AMBIENT_ADC)
  34                         goto found;
  35                 // TODO battery sense, etc.
  36         }
  37
  38         // all ADCs have been handled
  39         current_adc = LAST_ADC;
  40         return;
  41 found:
  42         // ADCSRB |= _BV(GSEL); // gain 8 or 32
  43         ADMUX = adc_mux[current_adc]; // set up mux, start one-shot conversion
  44         adc_ignore = 1; // ignore first reading after mux change
  45         ADCSRA |= _BV(ADSC);
  46 }
  47
  48 void init_adc()
  49 {
  50         current_adc = LAST_ADC;
  51         adc_ignore = 1;
  52
  53         ADCSRA = _BV(ADEN)                      // enable
  54                 | _BV(ADPS1) | _BV(ADPS0)       // CLK/8 = 125 kHz
  55                 // | _BV(ADPS2)                 // CLK/16 = 62.5 kHz
  56                 ;
  57         ADCSRB |= _BV(GSEL); // gain 8 or 32
  58
  59         // Disable digital input on all bits used by ADC
  60         DIDR0 = _BV(ADC0D) | _BV(ADC1D) | _BV(ADC2D) | _BV(ADC3D)
  61                 | _BV(ADC4D) | _BV(ADC5D);
  62
  63         ADCSRA |= _BV(ADSC);
  64
  65         /* Do first conversion and drop the result */
  66         while ((ADCSRA & _BV(ADIF)) == 0)
  67                 ;
  68         ADCSRA |= _BV(ADIF); // clear the IRQ flag
  69
  70         ADCSRA |= _BV(ADIE); // enable IRQ
  71 }
  72
  73 ISR(ADC_vect) { // IRQ handler
  74         uint16_t adcval = ADCW;
  75
  76 #if 0
  77         log_byte(0xF3);
  78         log_byte(current_adc);
  79         log_word(adcval);
  80 #endif
  81
  82         if (adc_ignore) {
  83                 ADCSRA |= _BV(ADSC);
  84                 adc_ignore = 0;
  85                 return;
  86         }
  87
  88         if (current_adc < N_PWMLEDS)
  89                 pwmled_adc(current_adc, adcval);
  90         if (current_adc == AMBIENT_ADC)
  91                 ambient_adc(adcval);
  92         // TODO battery sense, etc.
  93
  94         start_next_adc();
  95 }
  96
  97 void timer_start_adcs()
  98 {
  99         if (current_adc == LAST_ADC) // Don't start if in progress
 100                 start_next_adc();
 101 }
 102