firmware: emulate higher resolution of PWM

Emulate the sub-1 LSB resolution of PWM by updating the PWM values
in the timer interrupt routine

diff --git a/firmware/lights.h b/firmware/lights.h
index b159ae8cee2390bcd808a6b1a1bf2662fc161edb..434f0512d8c3d2a81fe5ad61d22549c0dcc35a99 100644 (file)
--- a/firmware/lights.h
+++ b/firmware/lights.h
@@ -29,11 +29,15 @@ void timer_start_adcs();
 
 /* pwm.c */
 #define PWM_MAX 0x1E4 /* This should be different than ADC frequency 125 kHz */
+#define PWM_STEP_SHIFT 2 /* second parameter of pwm_set is shifted by
+                         * PWM_STEP_SHIFT bits to the right before setting
+                         * into HW */
 
 void init_pwm();
 void susp_pwm();
 void pwm_off(unsigned char n);
 void pwm_set(unsigned char n, uint16_t stride);
+void pwm_timer();
 
 /* tmr.c */
 extern volatile uint16_t jiffies;

diff --git a/firmware/pwm.c b/firmware/pwm.c
index 201770f8152f440fe7ef21a219c336fb9f382b5f..da9fe3df679b9feb1faede1ed11205773890a824 100644 (file)
--- a/firmware/pwm.c
+++ b/firmware/pwm.c
@@ -4,8 +4,18 @@
 
 #include "lights.h"
 
+static uint16_t pwm[N_PWMLEDS];
+static volatile unsigned char step;
+
 void init_pwm()
 {
+       int i;
+
+       step = 0;
+
+       for (i = 0; i < N_PWMLEDS; i++)
+               pwm[n] = 0;
+
        /* Async clock */
        PLLCSR = _BV(PLLE);
 
@@ -37,6 +47,11 @@ void init_pwm()
 
 void susp_pwm()
 {
+       unsigned char i;
+
+       for (i = 0; i < N_PWMLEDS; i++)
+               pwm[i] = 0;
+
        DDRB &= ~(_BV( PB1 ) | _BV( PB3 ) | _BV( PB5 ));
        TCCR1D = TCCR1C = TCCR1B = TCCR1A = 0;
        TIMSK = 0;
@@ -45,6 +60,8 @@ void susp_pwm()
 
 void pwm_off(unsigned char n)
 {
+       pwm[n] = 0;
+
        switch (n) {
        case 0: DDRB &= ~_BV(PB1); break;
        case 1: DDRB &= ~_BV(PB3); break;
@@ -52,12 +69,10 @@ void pwm_off(unsigned char n)
        }
 }
 
-void pwm_set(unsigned char n, uint16_t stride)
+static void pwm_update_hw(unsigned char n)
 {
        unsigned char hi, lo;
-
-       if (stride > PWM_MAX)
-               stride = PWM_MAX;
+       uint16_t stride = (pwm[n] + step) >> PWM_STEP_SHIFT;
 
        if (n == 2)
                stride = PWM_MAX - stride;
@@ -84,6 +99,27 @@ void pwm_set(unsigned char n, uint16_t stride)
        }
 }
 
+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;
+
+       pwm[n] = stride;
+       pwm_update_hw(n);
+}
+
+void pwm_timer()
+{
+       unsigned char i;
+
+       if (++step >= (1 << PWM_STEP_SHIFT))
+               step = 0;
+
+       for (i = 0; i < N_PWMLEDS; i++)
+               if (pwm[n])
+                       pwm_update_hw(n);
+}
+
 #if 0
 static void inline pwm_handler()
 {

diff --git a/firmware/tmr.c b/firmware/tmr.c
index 5a94f9a40789c6fb0ddce0dd41b6ea6030135080..9a0a38b346b0adc00bb88a4d32e6df12fa0c549b 100644 (file)
--- a/firmware/tmr.c
+++ b/firmware/tmr.c
@@ -29,6 +29,8 @@ ISR(TIMER0_COMPA_vect)
 {
        ++jiffies;
 
+       pwm_timer();
+
        if (--pattern_div == 0) {
                timer_check_buttons();
                patterns_next_tick();