projects/step-up/adc.c

   1 #include <avr/io.h>
   2 #include <avr/interrupt.h>
   3 #include <avr/power.h>
   4 #include <avr/sleep.h>
   5
   6 #include "lights.h"
   7
   8 #define ZERO_ADC    2
   9
  10 //#define NUM_ADCS      ZERO_ADC
  11 #define NUM_ADCS        2
  12
  13 volatile static unsigned char current_adc;
  14 volatile unsigned char adc_enabled;
  15 volatile unsigned char need_battery_adc, need_pwmled_adc;
  16 static uint16_t adc_sum, read_zero, drop_count, read_count, n_reads_log;
  17 volatile uint16_t jiffies;
  18
  19 static void setup_mux(unsigned char n)
  20 {
  21         /* ADC numbering: PWM LEDs first, then others, zero at the end */
  22         switch (n) {
  23         case 0: // pwmled 1: 1.1V, ADC3 (PB3), single-ended
  24                 ADMUX = _BV(REFS1) | _BV(MUX1) | _BV(MUX0);
  25                 break;
  26         case 1: // battery voltage: 1.1V, ADC1 (PB2), single-ended
  27                 ADMUX = _BV(REFS1) | _BV(MUX0);
  28                 break;
  29         case ZERO_ADC: // zero: 1.1V, GND, single-ended
  30                 ADMUX = _BV(REFS1) | _BV(MUX3) | _BV(MUX2) | _BV(MUX0);
  31                 break;
  32         }
  33 }
  34
  35 void start_next_adc()
  36 {
  37         if (need_battery_adc) {
  38                 need_battery_adc = 0;
  39                 current_adc = 1;
  40                 read_zero = 1;
  41                 drop_count = 1;
  42                 read_count = 1;
  43                 n_reads_log = 0;
  44         } else if (need_pwmled_adc) {
  45                 current_adc = 0;
  46                 read_zero = 0;
  47                 drop_count = 1;
  48                 read_count = 1 << PWMLED_ADC_SHIFT;
  49                 n_reads_log = PWMLED_ADC_SHIFT;
  50         } else {
  51                 ADCSRA &= ~_BV(ADEN);
  52                 power_adc_disable();
  53                 adc_enabled = 0;
  54                 return;
  55         }
  56
  57         if (!adc_enabled) {
  58                 power_adc_enable();
  59                 ADCSRA |= _BV(ADEN);
  60                 adc_enabled = 1;
  61         }
  62
  63         adc_sum = 0;
  64
  65         // set up mux, start one-shot conversion
  66         if (read_zero)
  67                 setup_mux(ZERO_ADC);
  68         else
  69                 setup_mux(current_adc);
  70
  71         ADCSRA |= _BV(ADSC);
  72 }
  73
  74 #if 0
  75 void timer_start_slow_adcs()
  76 {
  77         if (current_slow_adc > N_PWMLEDS) { // Don't start if in progress
  78                 log_byte(0x80 + current_slow_adc);
  79         } else {
  80                 current_slow_adc = NUM_ADCS;
  81                 // TODO: kick the watchdog here
  82         }
  83 }
  84 #endif
  85
  86 /*
  87  * Single synchronous ADC conversion.
  88  * Has to be called with IRQs disabled (or with the ADC IRQ disabled).
  89  */
  90 static uint16_t read_adc_sync()
  91 {
  92         uint16_t rv;
  93
  94         ADCSRA |= _BV(ADSC); // start the conversion
  95
  96         // wait for the conversion to finish
  97         while((ADCSRA & _BV(ADIF)) == 0)
  98                 ;
  99
 100         rv = ADCW;
 101         ADCSRA |= _BV(ADIF); // clear the IRQ flag
 102
 103         return rv;
 104 }
 105
 106 void init_adc()
 107 {
 108         need_battery_adc = 0;
 109         need_pwmled_adc = 0;
 110         current_adc = 0;
 111         adc_enabled = 1;
 112
 113         power_adc_enable();
 114         ACSR |= _BV(ACD);       // but disable the analog comparator
 115
 116         ADCSRA = _BV(ADEN)                      // enable
 117                 | _BV(ADPS1) | _BV(ADPS0)       // CLK/8 = 125 kHz
 118                 // | _BV(ADPS2)                 // CLK/16 = 62.5 kHz
 119                 ;
 120         // ADCSRB |= _BV(GSEL); // gain 8 or 32
 121
 122         // Disable digital input on all bits used by ADC
 123         DIDR0 = _BV(ADC3D) | _BV(ADC2D);
 124
 125         // 1.1V, GND
 126         ADMUX = _BV(REFS1) | _BV(MUX3) | _BV(MUX2) | _BV(MUX0);
 127
 128         /* Do first conversion and drop the result */
 129         read_adc_sync();
 130
 131         ADCSRA |= _BV(ADIE); // enable IRQ
 132
 133         start_next_adc();
 134 }
 135
 136 void susp_adc()
 137 {
 138         ADCSRA = 0;
 139         DIDR0 = 0;
 140         power_adc_disable();
 141         adc_enabled = 0;
 142 }
 143
 144 ISR(ADC_vect) { // IRQ handler
 145         uint16_t adcval = ADCW;
 146
 147         if (read_zero) {
 148                 setup_mux(current_adc);
 149                 read_zero = 0;
 150                 ADCSRA |= _BV(ADSC); // drop this one, start the next
 151                 return;
 152         }
 153
 154         if (drop_count) {
 155                 ADCSRA |= _BV(ADSC); // drop this one, start the next
 156                 drop_count--;
 157                 return;
 158         }
 159
 160         if (read_count) {
 161                 ADCSRA |= _BV(ADSC); // immediately start the next conversion
 162                 adc_sum += adcval;
 163                 read_count--;
 164                 return;
 165         }
 166
 167         /*
 168          * Now we have performed read_count measurements and have them
 169          * in adc_sum.
 170          */
 171         switch (current_adc) {
 172         case 0:
 173                 // pwmled_adc(current_adc, adc_sum);
 174                 pwmled_adc(adc_sum);
 175                 break;
 176         case 1:
 177                 battery_adc(adc_sum);
 178                 break;
 179         }
 180
 181         start_next_adc();
 182 }