adc.c: sub-LSB resolution of PWM

Simulate a sub-LSB resolution inside the ADC IRQ handler. We do multiple
measurements of PWMLED resistor anyway, so it makes sense to modify the
PWM value after each reading. And indeed, experiments show less flicker
of PWM LEDs with this patch.

It is probably an overkill, and can be called only when measuring the
PWMLED output (and not ambient light sensor, for example). But it works
and it is simple enough.

diff --git a/firmware/adc.c b/firmware/adc.c
index 5ebc0a6d0d6076d224c594441773298ff48d6939..2bca0cf2e8cd8951acca37bbf04c6266fe787a5b 100644 (file)
--- a/firmware/adc.c
+++ b/firmware/adc.c
@@ -238,6 +238,7 @@ ISR(ADC_vect) { // IRQ handler
                ADCSRA |= _BV(ADSC);
                adc_sum += adcval;
                read_count--;
+               pwm_timer();
                return;
        }