pwm.c: channels running - visible from the outside

[bike-lights.git] / firmware / pwm.c

diff --git a/firmware/pwm.c b/firmware/pwm.c
index 56fb0884e125113a6885a3deb45cba9efe5ad6c8..27c8d0d0187d6e9a3f3e2a78448aefa7f0438843 100644 (file)
--- a/firmware/pwm.c
+++ b/firmware/pwm.c
@@ -1,12 +1,22 @@
 #include <avr/io.h>
 #include <avr/interrupt.h>
+#include <avr/power.h>
 #include <util/delay.h>
 #include <util/atomic.h>
 
 #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 > 0x3FF
+#error PWM_TOP too high
+#endif
+
+volatile unsigned char channels_running;
+
 static uint16_t pwm[N_PWMLEDS];
 static volatile unsigned char step;
+static unsigned char pll_enabled;
 
 static void enable_pll()
 {
@@ -18,6 +28,8 @@ static void enable_pll()
        while ((PLLCSR & _BV(PLOCK)) == 0)
                ;
        PLLCSR |= _BV(PCKE);
+
+       pll_enabled = 1;
 }
 
 void init_pwm()
@@ -25,12 +37,12 @@ void init_pwm()
        int i;
 
        step = 0;
+       channels_running = 0;
+       pll_enabled = 0;
 
        for (i = 0; i < N_PWMLEDS; i++)
                pwm[i] = 0;
 
-       enable_pll();
-
        // PWM channel D is inverted, ...
        TCCR1C = _BV(COM1D1) | _BV(COM1D0) | _BV(PWM1D);
        // PWM channels A and B are not
@@ -38,11 +50,11 @@ void init_pwm()
        TCCR1D = 0;
        TCCR1B = _BV(CS10);                     // no clock prescaling
 
-       TC1H = PWM_MAX >> 8;
-       OCR1C = PWM_MAX & 0xFF;                         // TOP value
+       TC1H = PWM_TOP >> 8;
+       OCR1C = PWM_TOP & 0xFF;                         // TOP value
 
-       TC1H = PWM_MAX >> 8;            // PWM3 is inverted
-       OCR1D = PWM_MAX & 0xFF;
+       TC1H = PWM_TOP >> 8;            // PWM3 is inverted
+       OCR1D = PWM_TOP & 0xFF;
 
        TC1H = 0x00;
        OCR1B = OCR1A = 0;              // initial stride is 0
@@ -70,6 +82,7 @@ void pwm_off(unsigned char n)
 {
        ATOMIC_BLOCK(ATOMIC_RESTORESTATE) {
                pwm[n] = 0;
+               channels_running &= ~(1 << n);
 
                switch (n) {
                case 0: DDRB &= ~_BV(PB1); break;
@@ -85,7 +98,7 @@ static void pwm_update_hw(unsigned char n)
        uint16_t stride = (pwm[n] + step) >> PWM_STEP_SHIFT;
 
        if (n == 2)
-               stride = PWM_MAX - stride;
+               stride = PWM_TOP - stride;
 
        hi = stride >> 8;
        lo = stride & 0xFF;
@@ -108,11 +121,17 @@ static void pwm_update_hw(unsigned char n)
 
 void pwm_set(unsigned char n, uint16_t stride)
 {
-       if (((stride + (1 << PWM_STEP_SHIFT)) >> PWM_STEP_SHIFT) >= PWM_MAX)
-               stride = PWM_MAX << PWM_STEP_SHIFT;
+       if (stride > PWM_MAX)
+               stride = PWM_MAX;
 
        ATOMIC_BLOCK(ATOMIC_RESTORESTATE) {
                pwm[n] = stride;
+               channels_running |= (1 << n);
+
+               if (!pll_enabled) {
+                       power_timer1_enable();
+                       enable_pll();
+               }
 
                pwm_update_hw(n);
 
@@ -136,3 +155,15 @@ void pwm_timer()
                        pwm_update_hw(i);
 }
 
+void pwm_disable_if_not_needed()
+{
+       if (channels_running)
+               return;
+
+       pll_enabled = 0;
+       DDRB &= ~(_BV(PB1) | _BV(PB3) | _BV(PB5));
+       PLLCSR &= ~(_BV(PLLE) | _BV(PCKE));
+
+       power_timer1_disable();
+}
+