projects/step-up/adc.c

   1 #include <avr/io.h>
   2 #include <avr/interrupt.h>
   3 #include <avr/sleep.h>
   4
   5 #include "lights.h"
   6
   7 #define ZERO_ADC    1
   8
   9 //#define NUM_ADCS      ZERO_ADC
  10 #define NUM_ADCS        1
  11
  12 volatile static unsigned char current_adc, current_slow_adc;
  13 static uint16_t adc_sum, read_zero, drop_count, read_count, n_reads_log;
  14
  15 static void setup_mux(unsigned char n)
  16 {
  17         /* ADC numbering: PWM LEDs first, then others, zero at the end */
  18         switch (n) {
  19         case 0: // pwmled 1: 1.1V, ADC3 (PB3), single-ended
  20                 ADMUX = _BV(REFS1) | _BV(MUX1) | _BV(MUX0);
  21                 break;
  22         case ZERO_ADC: // zero: 1.1V, GND, single-ended
  23                 ADMUX = _BV(REFS1) | _BV(MUX3) | _BV(MUX2) | _BV(MUX0);
  24                 break;
  25         }
  26 }
  27
  28 void start_next_adc()
  29 {
  30 #if 0
  31         if (current_adc == 0) {
  32                 if (current_slow_adc > N_PWMLEDS) {
  33                         // read one of the non-PWMLED ADCs
  34                         current_adc = --current_slow_adc;
  35                 } else {
  36                         // no more non-PWMLEDs to do, start with PWMLEDs
  37                         current_adc = N_PWMLEDS-1;
  38                 }
  39         } else if (current_adc >= N_PWMLEDS) {
  40                 // one of the non-PWMLED ADCs just finished, skip to PWMLEDs.
  41                 current_adc = N_PWMLEDS-1;
  42         } else {
  43                 // next PWMLED
  44                 current_adc--;
  45         }
  46 #else
  47         // single ADC for testing only
  48         current_adc = 0;
  49 #endif
  50
  51 #if 0
  52         log_byte(0x90 + current_adc); // debug ADC switching
  53 #endif
  54
  55         adc_sum = 0;
  56         read_zero = 0;
  57         drop_count = 1;
  58
  59         read_count = 1 << PWMLED_ADC_SHIFT;
  60         n_reads_log = PWMLED_ADC_SHIFT;
  61
  62         // set up mux, start one-shot conversion
  63         if (read_zero)
  64                 setup_mux(ZERO_ADC);
  65         else
  66                 setup_mux(current_adc);
  67
  68         ADCSRA |= _BV(ADSC);
  69 }
  70
  71 #if 0
  72 void timer_start_slow_adcs()
  73 {
  74         if (current_slow_adc > N_PWMLEDS) { // Don't start if in progress
  75                 log_byte(0x80 + current_slow_adc);
  76         } else {
  77                 current_slow_adc = NUM_ADCS;
  78                 // TODO: kick the watchdog here
  79         }
  80 }
  81 #endif
  82
  83 /*
  84  * Single synchronous ADC conversion.
  85  * Has to be called with IRQs disabled (or with the ADC IRQ disabled).
  86  */
  87 static uint16_t read_adc_sync()
  88 {
  89         uint16_t rv;
  90
  91         ADCSRA |= _BV(ADSC); // start the conversion
  92
  93         // wait for the conversion to finish
  94         while((ADCSRA & _BV(ADIF)) == 0)
  95                 ;
  96
  97         rv = ADCW;
  98         ADCSRA |= _BV(ADIF); // clear the IRQ flag
  99
 100         return rv;
 101 }
 102
 103 void init_adc()
 104 {
 105         current_slow_adc = NUM_ADCS;
 106         current_adc = 0;
 107
 108         ADCSRA = _BV(ADEN)                      // enable
 109                 | _BV(ADPS1) | _BV(ADPS0)       // CLK/8 = 125 kHz
 110                 // | _BV(ADPS2)                 // CLK/16 = 62.5 kHz
 111                 ;
 112         // ADCSRB |= _BV(GSEL); // gain 8 or 32
 113
 114         // Disable digital input on all bits used by ADC
 115         DIDR0 = _BV(ADC3D) | _BV(ADC2D);
 116
 117         // 1.1V, GND
 118         ADMUX = _BV(REFS1) | _BV(MUX3) | _BV(MUX2) | _BV(MUX0);
 119
 120         /* Do first conversion and drop the result */
 121         read_adc_sync();
 122
 123         ADCSRA |= _BV(ADIE); // enable IRQ
 124
 125         start_next_adc();
 126 }
 127
 128 #if 0
 129 void susp_adc()
 130 {
 131         ADCSRA = 0;
 132         DIDR0 = 0;
 133 }
 134
 135 static void adc1_gain20_adc(uint16_t adcsum)
 136 {
 137         // running average
 138         adc1_gain20_offset += adcsum
 139                         - (adc1_gain20_offset >> ADC1_GAIN20_OFFSET_SHIFT);
 140 }
 141 #endif
 142
 143 static void inline adc_based_timer()
 144 {
 145         static uint16_t pattern_counter;
 146
 147         if (++pattern_counter > 250) {
 148                 pattern_counter = 0;
 149                 patterns_next_tick();
 150         }
 151 }
 152
 153 ISR(ADC_vect) { // IRQ handler
 154         uint16_t adcval = ADCW;
 155
 156         adc_based_timer();
 157
 158         if (read_zero) {
 159                 setup_mux(current_adc);
 160                 read_zero = 0;
 161                 ADCSRA |= _BV(ADSC); // drop this one, start the next
 162                 return;
 163         }
 164
 165         if (drop_count) {
 166                 ADCSRA |= _BV(ADSC); // drop this one, start the next
 167                 drop_count--;
 168                 return;
 169         }
 170
 171         if (read_count) {
 172                 ADCSRA |= _BV(ADSC); // immediately start the next conversion
 173                 adc_sum += adcval;
 174                 read_count--;
 175                 return;
 176         }
 177
 178         /*
 179          * Now we have performed read_count measurements and have them
 180          * in adc_sum.
 181          */
 182         switch (current_adc) {
 183         case 0:
 184                 // pwmled_adc(current_adc, adc_sum);
 185                 pwmled_adc(adc_sum);
 186                 break;
 187         }
 188
 189         start_next_adc();
 190 }