From: Jan "Yenya" Kasprzak <kas@fi.muni.cz>
Date: Tue, 28 Aug 2012 19:57:41 +0000 (+0200)
Subject: ADC: ignore the first reading after MUX switch
X-Git-Tag: gedasymbols-20120913~50
X-Git-Url: https://www.fi.muni.cz/~kas/git//home/kas/public_html/git/?p=bike-lights.git;a=commitdiff_plain;h=f2662355cbf4bbf12904561a9258bab3e1b031bc

ADC: ignore the first reading after MUX switch
---

diff --git a/adc.c b/adc.c
index b758721..9a5e314 100644
--- a/adc.c
+++ b/adc.c
@@ -18,8 +18,9 @@ static unsigned char adc_mux[] = { // pwmleds should be first
 
 #define AMBIENT_ADC N_PWMLEDS
 
-#define LAST_ADC (sizeof(adc_mux)/sizeof(char))
-volatile static unsigned char current_adc = LAST_ADC;
+#define LAST_ADC (sizeof(adc_mux)/sizeof(adc_mux[0]))
+volatile static unsigned char current_adc;
+static unsigned char adc_ignore;
 
 static void start_next_adc()
 {
@@ -40,11 +41,15 @@ static void start_next_adc()
 found:
 	// ADCSRB |= _BV(GSEL); // gain 8 or 32
 	ADMUX = adc_mux[current_adc]; // set up mux, start one-shot conversion
+	adc_ignore = 1; // ignore first reading after mux change
 	ADCSRA |= _BV(ADSC);
 }
 
 void init_adc()
 {
+	current_adc = LAST_ADC;
+	adc_ignore = 1;
+
 	ADCSRA = _BV(ADEN)			// enable
 		| _BV(ADPS1) | _BV(ADPS0)	// CLK/8 = 125 kHz
 		// | _BV(ADPS2)			// CLK/16 = 62.5 kHz
@@ -68,6 +73,18 @@ void init_adc()
 ISR(ADC_vect) { // IRQ handler
 	uint16_t adcval = ADCW;
 
+#if 0
+	log_byte(0xF3);
+	log_byte(current_adc);
+	log_word(adcval);
+#endif
+
+	if (adc_ignore) {
+		ADCSRA |= _BV(ADSC);
+		adc_ignore = 0;
+		return;
+	}
+
 	if (current_adc < N_PWMLEDS)
 		pwmled_adc(current_adc, adcval);
 	if (current_adc == AMBIENT_ADC)