wip commenting

module05/ex00/adc.c

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+#include "header.h"
+
+// Table 14-6. Port C Pins Alternate Functions
+// - PC0 -> ADC0 (ADC Input Channel 0)
+//       -> PCINT8 (Pin Change Interrupt 8)
+//
+// 24.2 : The ADC generates a 10-bit result which is presented in the ADC Data Registers, ADCH and ADCL
+//
+// START A CONVERSTION in single conversion mode :
+// - disabling the Power Reduction ADC bit, PRADC
+// - writing a logical one to the ADC Start Conversion bit, ADSC
+
+#define ADC_PRESCALER	8
+
+void adc_init() {
+    ADMUX = (1 << REFS0);						// Table 24-3 : set voltage reference, AVCC with external capacitor at AREF pin
+    ADCSRA = (1 << ADEN) 						// 24.9.2 : enable ADC
+           | ADC_PRESCALE_SET(ADC_PRESCALER);	// Table 24-5 : prescaler ADC
+}
+
+uint16_t adc_read(uint8_t channel) {
+	CLEAR(PRR, PRADC);							// 24.3 : ensure power reduction is disabled for ADC, (10.11.3 : PRR – Power Reduction Register)
+    ADMUX = (ADMUX & 0xF0) | (channel & 0x0F);	// Select ADC channel
+    ADCSRA |= (1 << ADSC);						// 24.9.2 : Start conversion, ADSC: ADC Start Conversion
+    while (ADCSRA & (1 << ADSC));				// Wait for completion
+    return ADC;
+}