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TinyTouchLib.c
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TinyTouchLib.c
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/*
* tinytouchlib.c
*
* Created: 09.06.2013 17:25:47 - v0.1 Initial release (ATtiny 10)
* 10.06.2013 - v0.2 ported to ATtiny 25/45/85 and ATtiny13
* Author: Tim (cpldcpu@gmail.com)
*/
#include "TinyTouchLib.h"
#include <util/delay.h>
// Internal function to read the adc input
uint8_t tinytouch_adc(void);
uint16_t bias;
uint8_t touch;
#if touch_timeout>0
uint8_t timer;
#endif
/*
Capacitive sensing using charge sharing between
the S/H capacitor and an external sensing pad
*/
void tinytouch_init(void) {
#ifndef __AVR_ATtiny13__
PRR &=~_BV(PRADC);
#endif
ADCSRA =_BV(ADEN)|_BV(ADPS2)|_BV(ADPS1); // Enable ADC, Set prescaler to 64
bias=tinytouch_adc()<<8;
touch=0;
}
uint8_t tinytouch_sense(void) {
uint8_t i;
uint16_t tmp;
int16_t delta;
tmp=0;
for (i=0; i<16; i++) {
tmp+=tinytouch_adc(); // average 16 samples
_delay_us(100);
}
delta=tmp-(bias>>4);
if (!touch) {
if (delta>touch_threshold_on) {
touch=1;
#if touch_timeout>0
timer=0;
#endif
return tt_push;
}
// update bias only when touch not active
bias=(bias-(bias>>6))+(tmp>>2); // IIR low pass
return tt_off;
} else {
if (delta<touch_threshold_off) {
touch=0;
return tt_release;
}
#if touch_timeout>0
if (timer==255) {
bias=tinytouch_adc()<<8;
return tt_timeout;
}
timer++;
#endif
return tt_on;
}
}
uint8_t tinytouch_adc(void) {
uint8_t dat1,dat2;
// Precharge Low
ADMUX =tt_refadc; // connect S/H cap to reference pin
PORTB |= _BV(tt_refpin); // Charge S/H Cap
PORTB &=~_BV(tt_sensepin); // Discharge Pad (0)
DDRB |= _BV(tt_refpin)|_BV(tt_sensepin);
_delay_us(32);
DDRB &=~(_BV(tt_sensepin)); // float pad input, note that pull up is off.
#ifdef __AVR_ATtiny10__
ADMUX =tt_senseadc; // Connect sense input to adc
#else
ADMUX =tt_senseadc|_BV(ADLAR); // Connect sense input to adc
#endif
ADCSRA |=_BV(ADSC); // Start conversion
while (!(ADCSRA&_BV(ADIF)));
ADCSRA |=_BV(ADIF); // Clear ADIF
#ifdef __AVR_ATtiny10__
dat1=ADCL;
#else
dat1=ADCH;
#endif
// Precharge High
ADMUX =tt_refadc; // connect S/H cap to reference pin
PORTB &=~_BV(tt_refpin); // Discharge S/H Cap
PORTB |= _BV(tt_sensepin); // Charge Pad
DDRB |= _BV(tt_refpin)|_BV(tt_sensepin);
_delay_us(32);
DDRB &=~(_BV(tt_sensepin)); // float pad input input
PORTB &=~_BV(tt_sensepin); // pull up off
#ifdef __AVR_ATtiny10__
ADMUX =tt_senseadc; // Connect sense input to adc
#else
ADMUX =tt_senseadc|_BV(ADLAR); // Connect sense input to adc
#endif
ADCSRA |=_BV(ADSC); // Start conversion
while (!(ADCSRA&_BV(ADIF)));
ADCSRA |=_BV(ADIF); // Clear ADIF
#ifdef __AVR_ATtiny10__
dat2=ADCL;
#else
dat2=ADCH;
#endif
return dat2-dat1;
}