firmware/adc.c

   1 #include <avr/io.h>
   2 #include <avr/interrupt.h>
   3
   4 #include "lights.h"
   5
   6 /* ADC numbering: PWM LEDs first, then ambient light sensor, battery sensor */
   7 static unsigned char adc_mux[] = { // pwmleds should be first
   8         // 0: pwmled 1: 1.1V, ADC0,1 (PA0,1), gain 20
   9         _BV(REFS1) | _BV(MUX3) | _BV(MUX1) | _BV(MUX0),
  10         // 1: pwmled 2: 1.1V, ADC2,1 (PA2,1), gain 20
  11         _BV(REFS1) | _BV(MUX3) | _BV(MUX2) | _BV(MUX1),
  12         // 2: pwmled 3: 1.1V, ADC4 (PA5), single-ended
  13         _BV(REFS1) | _BV(MUX2),
  14         // 3: ambient light: 1.1V, ADC5 (PA6), single-ended
  15         _BV(REFS1) | _BV(MUX2) | _BV(MUX0),
  16         // 4: batt voltage: 1.1V, ADC6 (PA7), single-ended
  17         _BV(REFS1) | _BV(MUX2) | _BV(MUX1),
  18 };
  19
  20 #define AMBIENT_ADC N_PWMLEDS
  21 #define BATTERY_ADC (N_PWMLEDS + 1)
  22
  23 #define LAST_ADC (sizeof(adc_mux)/sizeof(adc_mux[0]))
  24 volatile static unsigned char current_adc;
  25 static unsigned char adc_ignore;
  26
  27 static void start_next_adc()
  28 {
  29         while (current_adc > 0) {
  30                 --current_adc;
  31
  32                 // test if current_adc should be measured
  33                 if (current_adc < N_PWMLEDS && pwmled_needs_adc(current_adc))
  34                         goto found;
  35                 if (current_adc == AMBIENT_ADC)
  36                         goto found;
  37                 // TODO battery sense, etc.
  38         }
  39
  40         // all ADCs have been handled
  41         current_adc = LAST_ADC;
  42         // TODO: kick the watchdog here.
  43         return;
  44 found:
  45         ADMUX = adc_mux[current_adc]; // set up mux, start one-shot conversion
  46         adc_ignore = 1; // ignore first reading after mux change
  47         ADCSRA |= _BV(ADSC);
  48 }
  49
  50 void init_adc()
  51 {
  52         current_adc = LAST_ADC;
  53         adc_ignore = 1;
  54
  55         ADCSRA = _BV(ADEN)                      // enable
  56                 | _BV(ADPS1) | _BV(ADPS0)       // CLK/8 = 125 kHz
  57                 // | _BV(ADPS2)                 // CLK/16 = 62.5 kHz
  58                 ;
  59         // ADCSRB |= _BV(GSEL); // gain 8 or 32
  60
  61         // Disable digital input on all bits used by ADC
  62         DIDR0 = _BV(ADC0D) | _BV(ADC1D) | _BV(ADC2D)
  63                 | _BV(ADC4D) | _BV(ADC5D) | _BV(ADC6D);
  64
  65         ADCSRA |= _BV(ADSC);
  66
  67         /* Do first conversion and drop the result */
  68         while ((ADCSRA & _BV(ADIF)) == 0)
  69                 ;
  70         ADCSRA |= _BV(ADIF); // clear the IRQ flag
  71
  72         ADCSRA |= _BV(ADIE); // enable IRQ
  73 }
  74
  75 void susp_adc()
  76 {
  77         ADCSRA = 0;
  78         DIDR0 = 0;
  79 }
  80
  81 ISR(ADC_vect) { // IRQ handler
  82         uint16_t adcval = ADCW;
  83
  84 #if 0
  85         log_byte(0xF3);
  86         log_byte(current_adc);
  87         log_word(adcval);
  88 #endif
  89
  90         if (adc_ignore) {
  91                 ADCSRA |= _BV(ADSC);
  92                 adc_ignore = 0;
  93                 return;
  94         }
  95
  96         if (current_adc < N_PWMLEDS)
  97                 pwmled_adc(current_adc, adcval);
  98         if (current_adc == AMBIENT_ADC)
  99                 ambient_adc(adcval);
 100         if (current_adc == BATTERY_ADC)
 101                 battery_adc(adcval);
 102
 103         start_next_adc();
 104 }
 105
 106 void timer_start_adcs()
 107 {
 108         if (current_adc == LAST_ADC) // Don't start if in progress
 109                 start_next_adc();
 110 }
 111