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(char))
  22 volatile static unsigned char current_adc = LAST_ADC;
  23
  24 static void start_next_adc()
  25 {
  26         while (current_adc > 0) {
  27                 --current_adc;
  28
  29                 // test if current_adc should be measured
  30                 if (current_adc < N_PWMLEDS && pwmled_is_on(current_adc))
  31                         goto found;
  32                 if (current_adc == AMBIENT_ADC)
  33                         goto found;
  34                 // TODO battery sense, etc.
  35         }
  36
  37         // all ADCs have been handled
  38         current_adc = LAST_ADC;
  39         return;
  40 found:
  41         // ADCSRB |= _BV(GSEL); // gain 8 or 32
  42         ADMUX = adc_mux[current_adc]; // set up mux, start one-shot conversion
  43         ADCSRA |= _BV(ADSC);
  44 }
  45
  46 void init_adc()
  47 {
  48         ADCSRA = _BV(ADEN)                      // enable
  49                 | _BV(ADPS1) | _BV(ADPS0)       // CLK/8 = 125 kHz
  50                 // | _BV(ADPS2)                 // CLK/16 = 62.5 kHz
  51                 ;
  52         ADCSRB |= _BV(GSEL); // gain 8 or 32
  53
  54         // Disable digital input on all bits used by ADC
  55         DIDR0 = _BV(ADC0D) | _BV(ADC1D) | _BV(ADC2D) | _BV(ADC3D)
  56                 | _BV(ADC4D) | _BV(ADC5D);
  57
  58         ADCSRA |= _BV(ADSC);
  59
  60         /* Do first conversion and drop the result */
  61         while ((ADCSRA & _BV(ADIF)) == 0)
  62                 ;
  63         ADCSRA |= _BV(ADIF); // clear the IRQ flag
  64
  65         ADCSRA |= _BV(ADIE); // enable IRQ
  66 }
  67
  68 ISR(ADC_vect) { // IRQ handler
  69         uint16_t adcval = ADCW;
  70
  71         if (current_adc < N_PWMLEDS)
  72                 pwmled_adc(current_adc, adcval);
  73         if (current_adc == AMBIENT_ADC)
  74                 ambient_adc(adcval);
  75         // TODO battery sense, etc.
  76
  77         start_next_adc();
  78 }
  79
  80 void timer_start_adcs()
  81 {
  82         if (current_adc == LAST_ADC) // Don't start if in progress
  83                 start_next_adc();
  84 }
  85