X-Git-Url: https://www.fi.muni.cz/~kas/git//home/kas/public_html/git/?p=tinyboard.git;a=blobdiff_plain;f=projects%2Fstep-up-1%2Fpwm.c;fp=projects%2Fstep-up-1%2Fpwm.c;h=b93a4fab8502039d73d811c69b96592725c5bad5;hp=0000000000000000000000000000000000000000;hb=9b7f892e6c70030468504d8a6da753bf1334ef94;hpb=aebe03ad223d877fed3f27fb4a3f459e2c947670

diff --git a/projects/step-up-1/pwm.c b/projects/step-up-1/pwm.c
new file mode 100644
index 0000000..b93a4fa
--- /dev/null
+++ b/projects/step-up-1/pwm.c
@@ -0,0 +1,74 @@
+#include <avr/io.h>
+#include <avr/interrupt.h>
+#include <avr/power.h>
+#include <util/delay.h>
+#include <util/atomic.h>
+
+#include "lights.h"
+
+/*
+ * Single PWM channel on OC1B (pin PB4 of Tiny45).
+ * Counts from 0 to 0xFF, without OCR1C compare.
+ */
+
+volatile unsigned char pwm_enabled;
+
+static void inline enable_pll()
+{
+	/* Async clock */
+	PLLCSR = _BV(PLLE) | _BV(LSM);
+
+	/* Synchronize to the phase lock */
+	_delay_us(100);
+	while ((PLLCSR & _BV(PLOCK)) == 0)
+		;
+	PLLCSR |= _BV(PCKE);
+}
+
+void init_pwm()
+{
+	pwm_enabled = 0;
+	power_timer1_enable();
+
+	TCCR1 = _BV(CTC1) | _BV(CS11);	// pll_clk/2
+	GTCCR = _BV(COM1B1) | _BV(PWM1B);
+
+	OCR1C = PWM_MAX;
+	OCR1B = 0;		// initial stride is 0
+
+	DDRB &= ~(_BV( PB4 ));
+	PORTB &= ~_BV(PB4); // set to zero
+}
+
+void susp_pwm()
+{
+	DDRB &= ~(_BV( PB4 ));
+	PORTB &= ~(_BV( PB4 ));
+	TCCR1 = 0;
+	TIMSK = 0;
+	TIFR = 0;
+
+	PLLCSR &= ~(_BV(PLLE) | _BV(PCKE));
+}
+
+void pwm_off()
+{
+	OCR1B = 0;
+	DDRB &= ~_BV(PB4);
+
+	PLLCSR &= ~(_BV(PLLE) | _BV(PCKE));
+	power_timer1_disable();
+	pwm_enabled = 0;
+}
+
+void pwm_set(uint8_t stride)
+{
+	OCR1B = stride;
+
+	if (!pwm_enabled) {
+		power_timer1_enable();
+		enable_pll();
+		DDRB |= _BV(PB4);
+		pwm_enabled = 1;
+	}
+}