pwm.c: single PWM channel only

Simplify it as much as possible - single PWM channel only, no
sub-LSB PWM value.

projects/step-up/lights.h

@@ -31,17 +31,11 @@ void susp_adc();
 void timer_start_slow_adcs();
 
 /* pwm.c */
-/*
- * The real Timer/Counter 1 frequency should not be too close to the
- * A/D converter frequency (125 kHz). Note that this is not the Top
- * value of T/C 1, it is shifted by PWM_STEP_SHIFT as described in pwm.c
- */
-#define PWM_MAX 0x340
+#define PWM_MAX 0xFF
 void init_pwm();
 void susp_pwm();
-void pwm_off(unsigned char n);
-void pwm_set(unsigned char n, uint16_t stride);
-void pwm_timer();
+void pwm_off();
+void pwm_set(uint8_t stride);
 
 /* tmr.c */
 extern volatile uint16_t jiffies;

projects/step-up/pwm.c

@@ -5,16 +5,12 @@
 
 #include "lights.h"
 
-#define PWM_STEP_SHIFT 2 /* sub-LSB precision */
-#define PWM_TOP (((PWM_MAX) + (4 << (PWM_STEP_SHIFT))) >> (PWM_STEP_SHIFT))
-#if PWM_TOP > 0x0FF
-#error PWM_TOP too high
-#endif
-
-static uint16_t pwm[N_PWMLEDS];
-static volatile unsigned char step;
+/*
+ * Single PWM channel on OC1B (pin PB4 of Tiny45).
+ * Counts from 0 to 0xFF, without OCR1C compare.
+ */
 
-static void enable_pll()
+static void inline enable_pll()
 {
 	/* Async clock */
 	PLLCSR = _BV(PLLE);
@@ -28,23 +24,16 @@ static void enable_pll()
 
 void init_pwm()
 {
-	int i;
-
-	step = 0;
-
-	for (i = 0; i < N_PWMLEDS; i++)
-		pwm[i] = 0;
-
 	enable_pll();
 
 	TCCR1 = _BV(CTC1) | _BV(CS10);	// no clock prescaling
-	GTCCR = _BV(COM1A1) | _BV(COM1B1) | _BV(PWM1A) | _BV(PWM1B);
+	GTCCR = _BV(COM1B1) | _BV(PWM1B);
 
-	OCR1C = PWM_TOP;
-	OCR1A = OCR1B = 0;		// initial stride is 0
+	OCR1C = PWM_MAX;
+	OCR1B = 0;		// initial stride is 0
 
-	DDRB  &= ~(_BV( PB1 ) | _BV( PB4 )); // tristate it
-	PORTB &= ~(_BV( PB1 ) | _BV( PB4 )); // set to zero
+	DDRB  &= ~_BV(PB4); // tristate it
+	PORTB &= ~_BV(PB4); // set to zero
 }
 
 #if 0
@@ -64,58 +53,14 @@ void susp_pwm()
 }
 #endif
 
-void pwm_off(unsigned char n)
+void pwm_off()
 {
-	ATOMIC_BLOCK(ATOMIC_RESTORESTATE) {
-		pwm[n] = 0;
-
-		switch (n) {
-		case 0: DDRB &= ~_BV(PB1); break;
-		case 1: DDRB &= ~_BV(PB4); break;
-		}
-	}
+	OCR1B = 0;
+	DDRB &= ~_BV(PB4);
 }
 
-static void pwm_update_hw(unsigned char n)
+void pwm_set(uint8_t stride)
 {
-	uint16_t stride = (pwm[n] + step) >> PWM_STEP_SHIFT;
-
-	switch (n) {
-	case 0:
-		OCR1A = stride;
-		break;
-	case 1:
-		OCR1B = stride;
-		break;
-	}
+	OCR1B = stride;
+	DDRB |= _BV(PB4);
 }
-
-void pwm_set(unsigned char n, uint16_t stride)
-{
-	if (stride > PWM_MAX)
-		stride = PWM_MAX;
-
-	ATOMIC_BLOCK(ATOMIC_RESTORESTATE) {
-		pwm[n] = stride;
-
-		pwm_update_hw(n);
-
-		switch(n) {
-		case 0: DDRB |= _BV(PB1); break;
-		case 1: DDRB |= _BV(PB4); break;
-		}
-	}
-}
-
-void pwm_timer()
-{
-	unsigned char i;
-
-	if (++step >= (1 << PWM_STEP_SHIFT))
-		step = 0;
-
-	for (i = 0; i < N_PWMLEDS; i++)
-		if (pwm[i])
-			pwm_update_hw(i);
-}
-

projects/step-up/pwmled.c

@@ -72,6 +72,7 @@ void init_pwmled()
 			led->err_sums[j] = 0;
 		}
 	}
+	pwmleds[0].state = ST_DISABLED;
 }
 
 void pwmled_set_mode(unsigned char n, unsigned char mode)
@@ -94,10 +95,10 @@ void pwmled_set_mode(unsigned char n, unsigned char mode)
 		led->pwm = led->mode_pwm[mode - 1];
 		led->err_sum = led->err_sums[mode - 1];
 		led->mode_changed = 1;
-		pwm_set(n, led->pwm);
+		pwm_set(led->pwm);
 	} else {
 		led->state = ST_OFF;
-		pwm_off(n);
+		pwm_off();
 	}
 }
 
@@ -135,7 +136,7 @@ static inline unsigned char pwmled_probed_ok(unsigned char n, uint16_t old_pwm)
 		unsigned char i;
 
 		led->state = ST_OFF;
-		pwm_off(n);
+		pwm_off();
 
 		log_byte(0xF0);
 		log_byte(n);
@@ -156,7 +157,7 @@ static inline unsigned char pwmled_probed_ok(unsigned char n, uint16_t old_pwm)
 static inline void pwmled_err(unsigned char n)
 {
 	pwmleds[n].state = ST_DISABLED;
-	pwm_off(n);
+	pwm_off();
 
 	log_byte(0xF1);
 	log_byte(n);
@@ -208,6 +209,6 @@ void pwmled_adc(unsigned char n, uint16_t adcval)
 	if (led->pwm == old_pwm)
 		return;
 
-	pwm_set(n, led->pwm);
+	pwm_set(led->pwm);
 }