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option for extra precision sacrificing bandwidth

This commit is contained in:
r4 2022-04-11 19:00:35 +02:00
parent 0a936c0147
commit 2fdeb72de7
1 changed files with 11 additions and 3 deletions
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14
spybug/spybug.ino
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@ -30,6 +30,8 @@
//#define ADC_PRESCALE_32 /* Up to ~27kHz. */
#define ADC_PRESCALE_64 /* Up to ~18kHz. */
#define U8_EXTRA_PRECISION /* (U8 sampling mode only) use 9th ADC reading bit and chop off 1st bit for more precision (sacrificing half of the bandwidth) */
#define RECORDING_DELAY_IN_MINUTES 0 /* Wait n minutes before starting to record. */
#define ADC_CHANNEL AdcChannel0
#define TIMER_COMPARE 1000 /* 16MHz / 1000 = 16kHz. */
@ -175,10 +177,16 @@ ISR(TIMER1_COMPA_vect) {
ISR(TIMER1_COMPB_vect) {
// Retrieve ADC Value and Write to Buffer
#if defined(SAMPLE_MODE_U8)
uint8_t adcval = ADCH;
#elif defined(SAMPLE_MODE_S16)
#ifdef U8_EXTRA_PRECISION
uint8_t l = ADCL; /* Read ADC registers. (Order matters!) */
uint8_t h = ADCH;
uint8_t adcval = (h << 7) | (l >> 1);
#else
uint8_t adcval = ADCH;
#endif
#elif defined(SAMPLE_MODE_S16)
uint8_t l = ADCL;
uint8_t h = ADCH;
int16_t adcval = (h << 8) | l;
adcval -= 0x0200; /* Make integer signed. */
adcval <<= 6; /* Turn 10-bit integer into 16-bit integer. */
@ -283,7 +291,7 @@ void setup() {
#endif
ADCSRB = _BV(ADTS2) | _BV(ADTS0); /* Auto-trigger source select: "Timer/Counter1 Compare Match B". */
ADMUX = _BV(REFS0) /* Use AREF pin (VCC by default) as reference voltage. */
#if defined(SAMPLE_MODE_U8)
#if defined(SAMPLE_MODE_U8) && !defined(U8_EXTRA_PRECISION)
| _BV(ADLAR) /* Left adjust ADC output so we only need to read ADCH. */
#endif
| (0xF & ADC_CHANNEL); /* Select our ADC input channel. */