From: Jan "Yenya" Kasprzak <kas@fi.muni.cz>
Date: Tue, 2 Jul 2013 10:06:26 +0000 (+0200)
Subject: adc.c: sub-LSB resolution of PWM
X-Git-Url: https://www.fi.muni.cz/~kas/git//home/kas/public_html/git/?p=bike-lights.git;a=commitdiff_plain;h=22f204ec3a908acbf879f36e2826eed281c5f2a6;hp=b34429defa04d493a49e24ad8840e42600bd0f28

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 5ebc0a6..2bca0cf 100644
--- 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;
 	}