From d8092ae891d96da4bf6daac37a6588150e6a724e Mon Sep 17 00:00:00 2001
From: Lars-Dominik Braun <lars@6xq.net>
Date: Tue, 27 May 2014 15:02:33 +0200
Subject: pwm: Initial LED PWM

---
 Makefile |  5 ++--
 main.c   | 22 +++++++-----------
 pwm.c    | 81 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 pwm.h    | 11 +++++++++
 4 files changed, 103 insertions(+), 16 deletions(-)
 create mode 100644 pwm.c
 create mode 100644 pwm.h

diff --git a/Makefile b/Makefile
index 8996720..1c28676 100644
--- a/Makefile
+++ b/Makefile
@@ -1,9 +1,10 @@
 MCU = atmega88
+CFLAGS=-Os
 
 all: sanduhr.hex
 
-sanduhr.elf: main.c i2c.c i2c.h uart.c uart.h timer.c timer.h gyro.c gyro.h accel.c accel.h common.h speaker.c speaker.h
-	avr-gcc -std=gnu99 -mmcu=$(MCU) -Os -o $@ $^
+sanduhr.elf: main.c i2c.c i2c.h uart.c uart.h timer.c timer.h gyro.c gyro.h accel.c accel.h common.h speaker.c speaker.h pwm.c pwm.h
+	avr-gcc -std=gnu99 -mmcu=$(MCU) $(CFLAGS) -o $@ $^
 
 sanduhr.hex: sanduhr.elf
 	avr-objcopy -O ihex -R .eeprom $< $@
diff --git a/main.c b/main.c
index 84aa75e..015abc3 100644
--- a/main.c
+++ b/main.c
@@ -14,19 +14,7 @@
 #include "gyro.h"
 #include "accel.h"
 #include "speaker.h"
-
-static void ledInit () {
-	/* set led1,led2 to output */
-	DDRB |= (1 << PB6) | (1 << PB7);
-	/* set led3,led4,led5,led6 to output */
-	DDRD |= (1 << PD2) | (1 << PD3) | (1 << PD4) | (1 << PD5);
-}
-
-/* show data with leds */
-static void ledShow (const unsigned char val) {
-	PORTB = (PORTB & ~((1 << PB6) | (1 << PB7))) | ((val & 0x3) << PB6);
-	PORTD = (PORTD & ~((1 << PD2) | (1 << PD3) | (1 << PD4) | (1 << PD5))) | (((val >> 2) & 0xf) << PD2);
-}
+#include "pwm.h"
 
 static void cpuInit () {
 	/* enter change prescaler mode */
@@ -45,12 +33,12 @@ static void cpuInit () {
 
 int main () {
 	cpuInit ();
-	ledInit ();
 	twInit ();
 	uartInit ();
 	gyroInit ();
 	accelInit ();
 	speakerInit ();
+	pwmInit ();
 	set_sleep_mode (SLEEP_MODE_IDLE);
 
 	printf ("initialization done\n");
@@ -59,6 +47,7 @@ int main () {
 	sei ();
 	gyroStart ();
 	accelStart ();
+	pwmStart ();
 
 #if 0
 	speakerStart ();
@@ -70,6 +59,10 @@ int main () {
 	bool checkGyro = false;
 	while (1) {
 		while (!timerHit ()) {
+			for (uint8_t i = 0; i < 6; i++) {
+				pwmSetBrightness (i, abs (gyroGetZTicks ()));
+			}
+
 			/* round-robin to prevent starvation */
 			if (checkGyro) {
 				gyroProcess ();
@@ -97,6 +90,7 @@ int main () {
 #endif
 	}
 	timerStop ();
+	pwmStop ();
 
 	printf ("stopped\n");
 
diff --git a/pwm.c b/pwm.c
new file mode 100644
index 0000000..eaaa5af
--- /dev/null
+++ b/pwm.c
@@ -0,0 +1,81 @@
+/*	LED pwm, uses timer0
+ *	XXX: this works, but we should use non-linear steps
+ */
+
+#include <avr/io.h>
+#include <avr/interrupt.h>
+#include <stdbool.h>
+
+#include "speaker.h"
+
+#define PWM_STEPS 16
+
+/* inverse brightness; 0 is max brightness, PWM_STEPS off */
+static uint8_t invbrightness[6];
+static uint8_t count = 0;
+
+ISR(TIMER0_COMPA_vect) {
+	if (count == 0) {
+		/* switch off all LEDs */
+		PORTB = PORTB & ~((1 << PB6) | (1 << PB7));
+		PORTD = PORTD & ~((1 << PD2) | (1 << PD3) | (1 << PD4) | (1 << PD5));
+	} else {
+		uint8_t pb = 0, pd = 0;
+		if (count > invbrightness[0]) {
+			pb |= (1 << PB6);
+		}
+		if (count > invbrightness[1]) {
+			pb |= (1 << PB7);
+		}
+		if (count > invbrightness[2]) {
+			pd |= (1 << PD2);
+		}
+		if (count > invbrightness[3]) {
+			pd |= (1 << PD3);
+		}
+		if (count > invbrightness[4]) {
+			pd |= (1 << PD4);
+		}
+		if (count > invbrightness[5]) {
+			pd |= (1 << PD5);
+		}
+		/* actually set them */
+		PORTB |= pb;
+		PORTD |= pd;
+	}
+	++count;
+	if (count >= PWM_STEPS) {
+		count = 0;
+	}
+}
+
+void pwmInit () {
+	/* set led1,led2 to output */
+	DDRB |= (1 << PB6) | (1 << PB7);
+	/* set led3,led4,led5,led6 to output */
+	DDRD |= (1 << PD2) | (1 << PD3) | (1 << PD4) | (1 << PD5);
+}
+
+void pwmStart () {
+	/* reset timer value */
+	TCNT0 = 0;
+	/* set ctc timer0 (part 1) */
+	TCCR0A = 0;
+	/* enable compare match interrupt */
+	TIMSK0 = (1 << OCIE0A);
+	/* compare value; interrupt on every tick */
+	OCR0A = 0;
+	/* io clock with 8 prescaler (>8 is too slow and starts flickering); ctc
+	 * (part 2) */
+	TCCR0B = (1 << CS01) | (1 << WGM02);
+}
+
+void pwmStop () {
+	/* zero clock source */
+	TCCR0B = 0;
+}
+
+void pwmSetBrightness (const uint8_t i, const uint8_t b) {
+	invbrightness[i] = b;
+}
+
diff --git a/pwm.h b/pwm.h
new file mode 100644
index 0000000..eeb93c6
--- /dev/null
+++ b/pwm.h
@@ -0,0 +1,11 @@
+#ifndef PWM_H
+#define PWM_H
+
+#include <stdint.h>
+void pwmInit ();
+void pwmStart ();
+void pwmStop ();
+void pwmSetBrightness (const uint8_t i, const uint8_t b);
+
+#endif /* PWM_H */
+
-- 
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