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 BATTERY_ADC (N_PWMLEDS + 0)
   9 #define BUTTON_ADC  (N_PWMLEDS + 1)
  10 #define ZERO_ADC    (N_PWMLEDS + 2)
  11
  12 //#define NUM_ADCS      ZERO_ADC
  13 #define NUM_ADCS        1
  14
  15 struct {
  16         unsigned char read_zero_log : 2;
  17         unsigned char read_drop_log : 2;
  18         unsigned char read_keep_log : 4;
  19 } adc_params[NUM_ADCS] = {
  20         { 0, 1, PWMLED_ADC_SHIFT },     // pwmled 1
  21 #if 0
  22         { 0, 1, PWMLED_ADC_SHIFT },     // pwmled 2
  23         { 0, 1, PWMLED_ADC_SHIFT },     // pwmled 3
  24         { 0, 1, AMBIENT_ADC_SHIFT },    // ambient
  25         { 0, 1, 0 },                    // battery
  26         { 0, 1, 0 },                    // gain20
  27         { 0, 1, 0 },                    // buttons
  28 #endif
  29 };
  30
  31 volatile static unsigned char current_adc, current_slow_adc;
  32 static uint16_t adc_sum, zero_count, drop_count, read_count, n_reads_log;
  33
  34
  35 static void setup_mux(unsigned char n)
  36 {
  37         /* ADC numbering: PWM LEDs first, then others, zero at the end */
  38         switch (n) {
  39         case 0: // pwmled 1: 1.1V, ADC3 (PB3), single-ended
  40                 ADMUX = _BV(REFS1) | _BV(MUX1) | _BV(MUX0);
  41                 break;
  42         case ZERO_ADC: // zero: 1.1V, GND, single-ended
  43                 ADMUX = _BV(REFS1) | _BV(MUX3) | _BV(MUX2) | _BV(MUX0);
  44                 break;
  45         }
  46 }
  47
  48 void start_next_adc()
  49 {
  50 #if 0
  51         if (current_adc == 0) {
  52                 if (current_slow_adc > N_PWMLEDS) {
  53                         // read one of the non-PWMLED ADCs
  54                         current_adc = --current_slow_adc;
  55                 } else {
  56                         // no more non-PWMLEDs to do, start with PWMLEDs
  57                         current_adc = N_PWMLEDS-1;
  58                 }
  59         } else if (current_adc >= N_PWMLEDS) {
  60                 // one of the non-PWMLED ADCs just finished, skip to PWMLEDs.
  61                 current_adc = N_PWMLEDS-1;
  62         } else {
  63                 // next PWMLED
  64                 current_adc--;
  65         }
  66 #else
  67         // single ADC for testing only
  68         current_adc = 0;
  69 #endif
  70
  71 #if 0
  72         log_byte(0x90 + current_adc); // debug ADC switching
  73 #endif
  74
  75         adc_sum = 0;
  76         // we use the last iteration of zero_count to set up the MUX
  77         // to its final destination, hence the "1 +" below:
  78         if (adc_params[current_adc].read_zero_log)
  79                 zero_count = 1 + (1 << (adc_params[current_adc].read_zero_log-1));
  80         else
  81                 zero_count = 1;
  82
  83         if (adc_params[current_adc].read_drop_log)
  84                 drop_count = 1 << (adc_params[current_adc].read_drop_log - 1);
  85         else
  86                 drop_count = 0;
  87
  88         read_count = 1 << adc_params[current_adc].read_keep_log;
  89         n_reads_log = adc_params[current_adc].read_keep_log;
  90
  91         // set up mux, start one-shot conversion
  92         if (zero_count > 1)
  93                 setup_mux(ZERO_ADC);
  94         else
  95                 setup_mux(current_adc);
  96
  97         ADCSRA |= _BV(ADSC);
  98 }
  99
 100 void timer_start_slow_adcs()
 101 {
 102         if (current_slow_adc > N_PWMLEDS) { // Don't start if in progress
 103                 log_byte(0x80 + current_slow_adc);
 104         } else {
 105                 current_slow_adc = NUM_ADCS;
 106                 // TODO: kick the watchdog here
 107         }
 108 }
 109
 110 /*
 111  * Single synchronous ADC conversion.
 112  * Has to be called with IRQs disabled (or with the ADC IRQ disabled).
 113  */
 114 static uint16_t read_adc_sync()
 115 {
 116         uint16_t rv;
 117
 118         ADCSRA |= _BV(ADSC); // start the conversion
 119
 120         // wait for the conversion to finish
 121         while((ADCSRA & _BV(ADIF)) == 0)
 122                 ;
 123
 124         rv = ADCW;
 125         ADCSRA |= _BV(ADIF); // clear the IRQ flag
 126
 127         return rv;
 128 }
 129
 130 void init_adc()
 131 {
 132         unsigned char i;
 133         current_slow_adc = NUM_ADCS;
 134         current_adc = 0;
 135
 136         power_adc_enable();
 137         ACSR |= _BV(ACD);       // but disable the analog comparator
 138
 139         ADCSRA = _BV(ADEN)                      // enable
 140                 | _BV(ADPS1) | _BV(ADPS0)       // CLK/8 = 125 kHz
 141                 // | _BV(ADPS2)                 // CLK/16 = 62.5 kHz
 142                 ;
 143         // ADCSRB |= _BV(GSEL); // gain 8 or 32
 144
 145         // Disable digital input on all bits used by ADC
 146         DIDR0 = _BV(ADC3D) | _BV(ADC2D);
 147
 148         // 1.1V, GND
 149         ADMUX = _BV(REFS1) | _BV(MUX3) | _BV(MUX2) | _BV(MUX0);
 150
 151         /* Do first conversion and drop the result */
 152         read_adc_sync();
 153
 154         ADCSRA |= _BV(ADIE); // enable IRQ
 155
 156         start_next_adc();
 157 }
 158
 159 #if 0
 160 void susp_adc()
 161 {
 162         ADCSRA = 0;
 163         DIDR0 = 0;
 164 }
 165
 166 static void adc1_gain20_adc(uint16_t adcsum)
 167 {
 168         // running average
 169         adc1_gain20_offset += adcsum
 170                         - (adc1_gain20_offset >> ADC1_GAIN20_OFFSET_SHIFT);
 171 }
 172 #endif
 173
 174 ISR(ADC_vect) { // IRQ handler
 175         uint16_t adcval = ADCW;
 176
 177         if (zero_count) {
 178                 if (zero_count > 1) {
 179                         ADCSRA |= _BV(ADSC);
 180                         zero_count--;
 181                         return;
 182                 } else {
 183                         setup_mux(current_adc);
 184                         zero_count = 0;
 185                         /* fall through */
 186                 }
 187         }
 188
 189         if (drop_count) {
 190                 ADCSRA |= _BV(ADSC); // drop this one, start the next
 191                 drop_count--;
 192                 return;
 193         }
 194
 195         if (read_count) {
 196                 ADCSRA |= _BV(ADSC);
 197                 adc_sum += adcval;
 198                 read_count--;
 199                 return;
 200         }
 201
 202         /*
 203          * Now we have performed read_count measurements and have them
 204          * in adc_sum.
 205          */
 206         switch (current_adc) {
 207         case 0:
 208                 // pwmled_adc(current_adc, adc_sum);
 209                 pwmled_adc(1, adc_sum);
 210                 break;
 211         }
 212
 213         start_next_adc();
 214 }