/* Soil Sensor Firmware
 * Soil Moisture and Vcc Measurement
 * Sensiplicity Systems
 * 
 *  Copyright 2015
 * 
 *  Department of Botany and Plant Pathology
 *  Center for Genome Research and Biocomputing
 *  Oregon State University
 *  Corvallis, OR 97331
 * 
 * This program is not free software; you can not redistribute it and/or
 * modify it at all.
 * 
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. */
#include <avr/interrupt.h>

/* This modules measure soil moisture using a capacitive voltage divider.
 * The 2Mhz clock signal is sent to a voltage divider with a 100k resistor
 * at the top and the variable capacitor pad at the bottom. The resulting
 * signal goes to a peak detector connected to the ADC. The peak detector
 * must be discharged manually, as it has no pull-down resistor. */

#define ADC_OVERSAMPLING_BITS 3 /* Number of bits to add (to the 10 bits of the ADC)
                                 * through oversampling. Each bit results in 
                                 * 4^OVERSAMPLING_BITS conversions per zone per measurement,
			         * with each conversion taking 104us */
#define ADC_AVERAGES 16 /* The number of oversampled values to average together for the final result. */

/* Initialize the ADC. */
void init_adc(void);

/* Get the number of zones on this device. */
uint8_t num_zones(void);

/* Measure the moisture level of a given zone. 
 * Returns a value between 0 and 2^(10 + OVERSAMPLING_BITS). 
 * Lower values indicate more moisture. */
uint16_t get_moisture(uint8_t zone);

/* Measure Vcc.
 * Returns Vcc in 1/32V increments. */
uint16_t get_vcc(void);