From 4c6ff89995f620aadb6cd8ef9403adac8ef48478 Mon Sep 17 00:00:00 2001 From: "Jan \"Yenya\" Kasprzak" Date: Sun, 17 Mar 2013 17:59:23 +0100 Subject: [PATCH] adc.c: configurable number of pre-readings When there is a supposed ADC noise problem, it is handful to drop several first readings, and even discharge the ADC capacitor by reading the single-ended wire connected to zero. This commit rewrites the ADC handling to allow exactly this, for each ADC input. --- firmware/adc.c | 139 ++++++++++++++++++++++++++++++++++--------------- 1 file changed, 98 insertions(+), 41 deletions(-) diff --git a/firmware/adc.c b/firmware/adc.c index 9cc1374..02af6b3 100644 --- a/firmware/adc.c +++ b/firmware/adc.c @@ -7,52 +7,60 @@ #define BATTERY_ADC (N_PWMLEDS + 1) #define ADC1_GAIN20 (N_PWMLEDS + 2) #define BUTTON_ADC (N_PWMLEDS + 3) +#define ZERO_ADC (N_PWMLEDS + 4) + +#define NUM_ADCS ZERO_ADC + +struct { + unsigned char read_zero_log : 2; + unsigned char read_drop_log : 2; + unsigned char read_keep_log : 4; +} adc_params[NUM_ADCS] = { + { 0, 1, PWMLED_ADC_SHIFT }, // pwmled 1 + { 0, 1, PWMLED_ADC_SHIFT }, // pwmled 2 + { 0, 1, PWMLED_ADC_SHIFT }, // pwmled 3 + { 0, 1, 3 }, // ambient + { 0, 1, 0 }, // battery + { 0, 1, 0 }, // gain20 + { 0, 1, 0 }, // buttons +}; -#define NUM_ADCS 7 volatile static unsigned char current_adc; -static uint16_t adc_sum; -static unsigned char sum_shift; -static unsigned char adc_vals; +static uint16_t adc_sum, zero_count, drop_count, read_count, n_reads_log; #define ADC1_GAIN20_OFFSET_SHIFT 6 static uint16_t adc1_gain20_offset; -static void inline setup_mux(unsigned char n) + +static void setup_mux(unsigned char n) { - /* ADC numbering: PWM LEDs first, then ambient light sensor, battery sensor */ + /* ADC numbering: PWM LEDs first, then others, zero at the end */ switch (n) { case 0: // pwmled 1: 1.1V, ADC0,1 (PA0,1), gain 20 ADMUX = _BV(REFS1) | _BV(MUX3) | _BV(MUX1) | _BV(MUX0); - sum_shift = PWMLED_ADC_SHIFT; break; case 1: // pwmled 2: 1.1V, ADC2,1 (PA2,1), gain 20 ADMUX = _BV(REFS1) | _BV(MUX3) | _BV(MUX2) | _BV(MUX1); - sum_shift = PWMLED_ADC_SHIFT; break; case 2: // pwmled 3: 1.1V, ADC4 (PA5), single-ended ADMUX = _BV(REFS1) | _BV(MUX2); - sum_shift = PWMLED_ADC_SHIFT; break; case AMBIENT_ADC: // ambient light: 1.1V, ADC5 (PA6), single-ended ADMUX = _BV(REFS1) | _BV(MUX2) | _BV(MUX0); - sum_shift = 3; // 3 measurements break; case BATTERY_ADC: // batt voltage: 1.1V, ADC6 (PA7), single-ended ADMUX = _BV(REFS1) | _BV(MUX2) | _BV(MUX1); - sum_shift = 0; // 1 measurement break; case ADC1_GAIN20: // gain stage offset: 1.1V, ADC1,1, gain 20 ADMUX = _BV(REFS1) | _BV(MUX3) | _BV(MUX2) | _BV(MUX0); - sum_shift = 0; // 1 measurement break; case BUTTON_ADC: // buttons: 1.1V, ADC3, single-ended PORTA |= _BV(PA3); // +5V to the voltage splitter ADMUX = _BV(REFS1) | _BV(MUX1) | _BV(MUX0); - sum_shift = 0; + break; + case ZERO_ADC: // zero: 1.1V, ADC1 (PA1), single-ended + ADMUX = _BV(REFS1) | _BV(MUX0); break; } - - adc_sum = 0; - adc_vals = 1 << sum_shift; } static void start_next_adc() @@ -63,8 +71,28 @@ static void start_next_adc() // TODO: kick the watchdog here. current_adc = NUM_ADCS-1; + adc_sum = 0; + // we use the last iteration of zero_count to set up the MUX + // to its final destination, hence the "1 +" below: + if (adc_params[current_adc].read_zero_log) + zero_count = 1 + (1 << (adc_params[current_adc].read_zero_log-1)); + else + zero_count = 1; + + if (adc_params[current_adc].read_drop_log) + drop_count = 1 << (adc_params[current_adc].read_drop_log - 1); + else + drop_count = 0; + + read_count = 1 << adc_params[current_adc].read_keep_log; + n_reads_log = adc_params[current_adc].read_keep_log; + // set up mux, start one-shot conversion - setup_mux(current_adc); + if (zero_count > 1) + setup_mux(ZERO_ADC); + else + setup_mux(current_adc); + ADCSRA |= _BV(ADSC); } @@ -127,48 +155,77 @@ void susp_adc() DIDR0 = 0; } +static void adc1_gain20_adc(uint16_t adcsum) +{ + // running average + adc1_gain20_offset += adcsum + - (adc1_gain20_offset >> ADC1_GAIN20_OFFSET_SHIFT); +} + ISR(ADC_vect) { // IRQ handler uint16_t adcval = ADCW; - if (adc_vals) - // start the next conversion immediately - ADCSRA |= _BV(ADSC); - - if (adc_vals < (1 << sum_shift)) - // drop the first conversion, use all others - adc_sum += adcval; + if (zero_count) { + if (zero_count > 1) { + ADCSRA |= _BV(ADSC); + zero_count--; + return; + } else { + setup_mux(current_adc); + zero_count = 0; + /* fall through */ + } + } - if (adc_vals) { - adc_vals--; + if (drop_count) { + ADCSRA |= _BV(ADSC); // drop this one, start the next + drop_count--; return; } - // Now handle the (1 << sum_shift) measurements + if (read_count) { + ADCSRA |= _BV(ADSC); + adc_sum += adcval; + read_count--; + return; + } - adcval = adc_sum >> sum_shift; + /* + * Now we have performed read_count measurements and have them + * in adc_sum. + */ - if (current_adc == ADC1_GAIN20) { - // running average - adc1_gain20_offset += adcval - - (adc1_gain20_offset >> ADC1_GAIN20_OFFSET_SHIFT); - } else if (current_adc == 0 || current_adc == 1) { + // For inputs with gain, subtract the measured gain stage offset + if (current_adc < 2) { uint16_t offset = adc1_gain20_offset - >> (ADC1_GAIN20_OFFSET_SHIFT - sum_shift); + >> (ADC1_GAIN20_OFFSET_SHIFT - n_reads_log); + if (adc_sum > offset) adc_sum -= offset; else adc_sum = 0; } - if (current_adc < N_PWMLEDS) + switch (current_adc) { + case 0: + case 1: + case 2: pwmled_adc(current_adc, adc_sum); - if (current_adc == AMBIENT_ADC) + break; + case AMBIENT_ADC: ambient_adc(adc_sum); - if (current_adc == BATTERY_ADC) - battery_adc(adcval); - if (current_adc == BUTTON_ADC) - button_adc(adcval); - + break; + case BATTERY_ADC: + battery_adc(adc_sum); + break; + case BUTTON_ADC: + button_adc(adc_sum); + break; + case ADC1_GAIN20: + adc1_gain20_adc(adcval); + break; + } + start_next_adc(); } -- 2.39.3