diff options
Diffstat (limited to 'spaghetti-monster')
| -rw-r--r-- | spaghetti-monster/fsm-adc.c | 107 |
1 files changed, 43 insertions, 64 deletions
diff --git a/spaghetti-monster/fsm-adc.c b/spaghetti-monster/fsm-adc.c index 9db79e7..c686694 100644 --- a/spaghetti-monster/fsm-adc.c +++ b/spaghetti-monster/fsm-adc.c @@ -25,7 +25,7 @@ static inline void set_admux_therm() { #if (ATTINY == 1634) ADMUX = ADMUX_THERM; #elif (ATTINY == 25) || (ATTINY == 45) || (ATTINY == 85) - ADMUX = ADMUX_THERM | (1 << ADLAR); + ADMUX = ADMUX_THERM; #elif (ATTINY == 841) // FIXME: not tested ADMUXA = ADMUXA_THERM; ADMUXB = ADMUXB_THERM; @@ -46,9 +46,9 @@ inline void set_admux_voltage() { #endif #elif (ATTINY == 25) || (ATTINY == 45) || (ATTINY == 85) #ifdef USE_VOLTAGE_DIVIDER // 1.1V / pin7 - ADMUX = ADMUX_VOLTAGE_DIVIDER | (1 << ADLAR); + ADMUX = ADMUX_VOLTAGE_DIVIDER; #else // VCC / 1.1V reference - ADMUX = ADMUX_VCC | (1 << ADLAR); + ADMUX = ADMUX_VCC; #endif #elif (ATTINY == 841) // FIXME: not tested #ifdef USE_VOLTAGE_DIVIDER // 1.1V / pin7 @@ -88,7 +88,7 @@ inline void ADC_on() #endif #if (ATTINY == 1634) ACSRA |= (1 << ACD); // turn off analog comparator to save power - ADCSRB |= (1 << ADLAR); // left-adjust flag is here instead of ADMUX + //ADCSRB |= (1 << ADLAR); // left-adjust flag is here instead of ADMUX #endif // enable, start, auto-retrigger, prescale ADCSRA = (1 << ADEN) | (1 << ADSC) | (1 << ADATE) | ADC_PRSCL; @@ -113,7 +113,7 @@ inline void ADC_off() { static inline uint8_t calc_voltage_divider(uint16_t value) { // use 9.7 fixed-point to get sufficient precision uint16_t adc_per_volt = ((ADC_44<<7) - (ADC_22<<7)) / (44-22); - // incoming value is left-adjusted, so shift it into a matching position + // shift incoming value into a matching position uint8_t result = ((value>>1) / adc_per_volt) + VOLTAGE_FUDGE_FACTOR; return result; } @@ -134,40 +134,41 @@ static inline uint8_t calc_voltage_divider(uint16_t value) { #endif // happens every time the ADC sampler finishes a measurement +// collects an average of 64 samples, which increases effective number of +// bits from 10 to about 16 (ish, probably more like 14 really) +// (64 was chosen because it's the largest sample size which allows the +// sum to still fit into a 16-bit integer, and for speed and size reasons, +// we want to avoid doing 32-bit math) ISR(ADC_vect) { - // slow down even more than ADC_PRSCL - // (result is about 600 Hz or a maximum of ~9 ADC units per second) - // (8 MHz / 128 prescale / 13.5 ticks per measurement / 8 = ~578 Hz) - // (~578 Hz / 64X resolution = ~9 original-resolution units per second) - if (1 == (adc_sample_count & 7)) { + static uint16_t adc_sum; - uint16_t m; // latest measurement - uint16_t s; // smoothed measurement - uint8_t channel = adc_channel; + // keep this moving along + adc_sample_count ++; + // reset on first sample + // also, ignore first value since it's probably junk + if (1 == adc_sample_count) { + adc_sum = 0; + return; + } + // 64 samples collected, save the result + else if (66 == adc_sample_count) { + adc_smooth[adc_channel] = adc_sum; + } + // add the latest measurement to the pile + else { + uint16_t m = ADC; + // add to the running total + adc_sum += m; // update the latest value - m = ADC; - adc_raw[channel] = m; - - // lowpass the value - //s = adc_smooth[channel]; // easier to read - uint16_t *v = adc_smooth + channel; // compiles smaller - s = *v; - if (m > s) { s++; } - if (m < s) { s--; } - //adc_smooth[channel] = s; - *v = s; - - // track what woke us up, and enable deferred logic - irq_adc = 1; - + adc_raw[adc_channel] = m; } + // don't worry about the running total overflowing after sample 64... + // it doesn't matter - // the next measurement isn't the first - //adc_sample_count = 1; - adc_sample_count ++; - + // track what woke us up, and enable deferred logic + irq_adc = 1; } void adc_deferred() { @@ -177,7 +178,7 @@ void adc_deferred() { // real-world entropy makes this a true random, not pseudo // Why here instead of the ISR? Because it makes the time-critical ISR // code a few cycles faster and we don't need crypto-grade randomness. - pseudo_rand_seed += (ADCL >> 6) + (ADCH << 2); + pseudo_rand_seed += ADCL; #endif // the ADC triggers repeatedly when it's on, but we only need to run the @@ -241,22 +242,11 @@ static inline void ADC_voltage_handler() { #define LVP_TIMER_START (VOLTAGE_WARNING_SECONDS*ADC_CYCLES_PER_SECOND) // N seconds between LVP warnings #define LVP_LOWPASS_STRENGTH ADC_CYCLES_PER_SECOND // lowpass for one second - uint16_t measurement = adc_smooth[0]; // latest 16-bit ADC value - - // jump-start the lowpass seed at boot - // (otherwise it takes a while to rise from zero) - if (measurement < 255) { - measurement = adc_raw[0]; - adc_smooth[0] = measurement; - } + uint16_t measurement; - // values stair-step between intervals of 64, with random variations - // of 1 or 2 in either direction, so if we chop off the last 6 bits - // it'll flap between N and N-1... but if we add half an interval, - // the values should be really stable after right-alignment - // (instead of 99.98, 100.00, and 100.02, it'll hit values like - // 100.48, 100.50, and 100.52... which are stable when truncated) - measurement += 32; + // latest ADC value + if (go_to_standby) measurement = adc_raw[0] << 6; + else measurement = adc_smooth[0]; #ifdef USE_VOLTAGE_DIVIDER voltage = calc_voltage_divider(measurement); @@ -264,7 +254,6 @@ static inline void ADC_voltage_handler() { // calculate actual voltage: volts * 10 // ADC = 1.1 * 1024 / volts // volts = 1.1 * 1024 / ADC - //voltage = (uint16_t)(1.1*1024*10)/measurement + VOLTAGE_FUDGE_FACTOR; voltage = ((uint16_t)(2*1.1*1024*10)/(measurement>>6) + VOLTAGE_FUDGE_FACTOR) >> 1; #endif @@ -308,34 +297,24 @@ static inline void ADC_temperature_handler() { #define OVERHEAT_LOWPASS_STRENGTH (ADC_CYCLES_PER_SECOND*2) // lowpass for 2 seconds #define UNDERHEAT_LOWPASS_STRENGTH (ADC_CYCLES_PER_SECOND*2) // lowpass for 2 seconds - // latest 16-bit ADC reading (left-adjusted, lowpassed) + // latest 16-bit ADC reading uint16_t measurement; if (! reset_thermal_history) { - measurement = adc_smooth[1]; // average of recent samples + // average of recent samples + measurement = adc_smooth[1]; } else { // wipe out old data // don't keep resetting reset_thermal_history = 0; - // ignore lowpass, use latest sample - measurement = adc_raw[1]; - - // reset lowpass to latest sample - adc_smooth[1] = measurement; + // ignore average, use latest sample + measurement = adc_raw[1] << 6; // forget any past measurements for(uint8_t i=0; i<NUM_THERMAL_VALUES_HISTORY; i++) temperature_history[i] = measurement; } - // values stair-step between intervals of 64, with random variations - // of 1 or 2 in either direction, so if we chop off the last 6 bits - // it'll flap between N and N-1... but if we add half an interval, - // the values should be really stable after right-alignment - // (instead of 99.98, 100.00, and 100.02, it'll hit values like - // 100.48, 100.50, and 100.52... which are stable when truncated) - measurement += 32; - { // rotate the temperature history // if it's time to rotate the thermal history, do it // FIXME? allow more than 255 frames per step |