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