From 5a12804f1173a21db44a671e2c74be9c6e76f394 Mon Sep 17 00:00:00 2001
From: Robin Krens <robin@robinkrens.nl>
Date: Fri, 20 May 2022 14:30:50 +0200
Subject: [PATCH] hbc: sensor based on back emf

- voltage divider for ~1.6V
- AIN0 and AIN1: AIN1 has LRA and checks if treshold is above 1.6
---
 hbc.c | 71 ++++++++++++++++++++++++++++++++++++++++---------------------------
 1 file changed, 43 insertions(+), 28 deletions(-)

diff --git a/hbc.c b/hbc.c
index 6080410..c5c2c0d 100644
--- a/hbc.c
+++ b/hbc.c
@@ -1,5 +1,6 @@
 #include <stdio.h>
 #include <stdlib.h>
+#include <stdbool.h>
 #include <avr/io.h>
 #include <avr/wdt.h>
 #include <avr/sleep.h>
@@ -8,17 +9,17 @@
 #include <util/delay.h>
 #include "haptic.h"
 	
-volatile int xvar = 1;
-
-/* idle mode will wake up board and will
- * return PC after latest sleep_mode() call */
-EMPTY_INTERRUPT(SIG_COMPARATOR);
-
-ISR(TIM0_COMPA_vect)
-{	
-	xvar++;
+ISR(SIG_COMPARATOR)
+{
+	if (ACSR & (1 << ACO)) {
+		PORTB |= (1 << PB4);
+	} else {
+		PORTB &= ~(1 << PB4);
+	}
 }
 
+EMPTY_INTERRUPT(TIM0_COMPA_vect);
+
 static void switch_idle(void)
 {
 	sei();
@@ -35,33 +36,47 @@ static void init_board(void)
 	 * When the bandgap reference is connected to the Analog Comparator (by setting the ACBG bit in ACSR). */
 }
 
+static void set_ref_voltage(void)
+{
+	DDRB |= (1 << DDB1); /* set PB0 as output */
+	TCCR0A = TCCR0B = 0;
+	TCCR0A |= (1 << WGM01) | (1 << WGM00) | (1 << COM0B1);
+	TCCR0B |= (1 << CS00); /* clk/1024 prescaler */
+	OCR0B = 0x20; /* 25% duty cycle */
+	TCNT0 = 0;
+	TIMSK = (1 << OCIE0B); /* enable interrupts for overflow and compare */
+}
+
+static void config_comparator(void)
+{
+	ADCSRA = 0;
+	ADCSRB |= (1 << ACME); /* multiplex enable */
+	
+	//ADMUX |= (1 << MUX0); /* ADC1 as negative input */
+	
+	ACSR &= ~(1 << ACD); /* enable comparator */
+	//ACSR |= (1 << ACBG);
+	//ACSR |= (1 << ACIS1) | (1 << ACIS0);
+
+	DIDR0 |= (1 << AIN1D) | (1 << AIN0D);
+
+	ACSR |= (1 << ACIE); /* enable interrupts */
+}
+
 int main(void)
 {
 	init_board();
-	xvar = 1;	
+
+	DDRB |= (1 << DDB4);
+	//PORTB |= (1 << PB1);
+
 	cli();
-	DDRB |= (1 << DDB0); /* set PB0 as output */
-	TCCR0A = TCCR0B = 0;
-	TCCR0A |= (1 << WGM01) | (1 << WGM00) | (1 << COM0A1);
-	TCCR0B |= (1 << CS02) | (1 << CS00); /* clk/1024 prescaler */
-	OCR0A = 0x7F; /* 50% duty cycle */
-	TCNT0 = 0;
-	TIMSK = (1 << OCIE0A); /* enable interrupts for overflow and compare */
+	//set_ref_voltage();
+	config_comparator();
 	sei();
 
 	while(1) {
 		_delay_ms(100);
-		/* set LRA as sensor and switch to idle mode
-		 * check back-EMF of LRA: if treshold is surpassed
-		 * comparator intterupt is triggered */
-//		set_lra_as_sensor();
-//		switch_idle(); 
-//
-//		/* board wakes up, set LRA as actuator and
-//		 * plays haptic effect */
-//		set_lra_as_actuator();
-//		play_haptic();
-
 	}
 
 }
-- 
2.7.4