added cleaned up and tested ADC support library

CMakeLists.txt

@@ -13,6 +13,8 @@ set(SOURCE_FILES
         lib/nsdelay.h
         lib/spi.c
         lib/spi.h
+        lib/adc.c
+        lib/adc.h
         lib/usart.c
         lib/usart.h
         )

Makefile

@@ -29,6 +29,7 @@ OBJS  = $(BINARY).o
 OBJS += lib/usart.o
 OBJS += lib/iopins.o
 OBJS += lib/spi.o
+OBJS += lib/adc.o
 
 # Dirs with header files
 INCL_DIRS = . lib/

lib/adc.c

@@ -0,0 +1,49 @@
+#include <avr/io.h>
+#include <stdint.h>
+
+#include "calc.h"
+#include "adc.h"
+
+/** Initialize the ADC */
+void adc_init(enum ADC_Prescaller presc)
+{
+	ADCSRA |= presc;  // 128 prescaler -> 125 kHz
+	ADMUX  |= _BV(REFS0);  // Voltage reference
+	sbi(ADCSRA, ADEN);  // Enable ADC
+}
+
+/** Disable ADC */
+void adc_disable(void)
+{
+	cbi(ADCSRA, ADEN);
+}
+
+/** Enable ADC */
+void adc_enable(void)
+{
+	sbi(ADCSRA, ADEN);
+}
+
+static void adc_convert(uint8_t channel)
+{
+	set_low_nibble(ADMUX, channel);  // Select channel to sample
+	sbi(ADMUX, ADLAR);  // Align result to left
+	sbi(ADCSRA, ADSC);  // Start conversion
+
+	while (bit_is_high(ADCSRA, ADSC)); // Wait for it...
+}
+
+/** Sample analog pin with 8-bit precision */
+uint8_t adc_read_byte(uint8_t channel)
+{
+	adc_convert(channel);
+	return ADCH;  // The upper 8 bits of ADC result
+}
+
+
+/** Sample analog pin with 10-bit precision */
+uint16_t adc_read_word(uint8_t channel)
+{
+	adc_convert(channel);
+	return ADCW;  // The whole ADC word (10 bits)
+}

lib/adc.h

@@ -0,0 +1,32 @@
+#pragma once
+
+//
+// Utilities for build-in A/D converter
+//
+
+#include <stdint.h>
+
+enum ADC_Prescaller {
+	ADC_PRESC_2 = 1,
+	ADC_PRESC_4 = 2,
+	ADC_PRESC_8 = 3,
+	ADC_PRESC_16 = 4,
+	ADC_PRESC_32 = 5,
+	ADC_PRESC_64 = 6,
+	ADC_PRESC_128 = 7,
+};
+
+/** Initialize the ADC and enable it */
+void adc_init(enum ADC_Prescaller presc);
+
+/** Disable ADC (for power saving) */
+void adc_disable(void);
+
+/** Enable (already initialized) ADC */
+void adc_enable(void);
+
+/** Sample analog pin with 8-bit precision */
+uint8_t adc_read_byte(uint8_t channel);
+
+/** Sample analog pin with 10-bit precision */
+uint16_t adc_read_word(uint8_t channel);