#include <stdio.h>
#include <unistd.h>
#include <string.h>
#include <math.h>
#include <stdint.h>
#include <onewire.h>
#include <ds2438.h>

float ds2438_convert_voltage(const struct owaddr *addr)
{
	unsigned char buf[9];
	ow_matchrom(addr);
	ow_writecommand(DS2438_CONV_V);
	usleep(10000);
	
	if (!ds2438_readsp(addr, 0, buf))
		return NAN;
	
	return (((int)buf[4] << 8) | buf[3]) * 0.01f;
}

/* Public functions */

bool ds2438_readsp(const struct owaddr *addr, int page, unsigned char *buf) {
	// Read 8-byte stratchpad page and verifies CRC. Returns false on failure.
	
	ow_matchrom(addr);
	ow_writecommand(DS2438_RECALL);
	ow_writecommand(page);
	
	ow_matchrom(addr);
	ow_writecommand(DS2438_READSP);
	ow_writecommand(page);
	ow_readbytes(buf, 9);
	
	return ow_crc(buf, 9) == 0;
}

bool ds2438_writesp(const struct owaddr *addr, int page, const unsigned char *buf) {
	// Write 8-byte stratchpad page and verify. Returns false on failure.
	ow_matchrom(addr);
	ow_writecommand(DS2438_WRITESP);
	ow_writecommand(page);
	ow_writebytes(buf, 8);
	
	unsigned char verifybuf[8];
	return (ds2438_readsp(addr, page, verifybuf)
		&& memcmp(buf, verifybuf, 8) == 0);
}

bool ds2438_config(const struct owaddr *addr, unsigned char config) {
	// Write and verify just one byte of the first page.
	
	ow_matchrom(addr);
	ow_writecommand(DS2438_WRITESP);
	ow_writecommand(0);
	ow_writecommand(config);
	
	unsigned char buf;
	ow_matchrom(addr);
	ow_writecommand(DS2438_READSP);
	ow_writecommand(0);
	ow_readbytes(&buf, 1);
	
	return buf == config;
}

float ds2438_temperature(const struct owaddr *addr) {
	unsigned char buf[9];
	
	ow_matchrom(addr);
	ow_writecommand(DS2438_CONV_T);
	
	usleep(10000);
	
	if (!ds2438_readsp(addr, 0, buf))
		return NAN;
	
	float result;
	result = (int16_t)((buf[2] << 8) | buf[1]) / 256.0f;
	return result;
}

float ds2438_humidity(const struct owaddr *addr) {
	float vdd, vout, temperature, rh;
	
	if (!ds2438_config(addr, DS2438_CONF_AD))
		return NAN;
	vdd = ds2438_convert_voltage(addr);
	
	if (!ds2438_config(addr, 0))
		return NAN;
	vout = ds2438_convert_voltage(addr);
	
	temperature = ds2438_temperature(addr);
	
	// Sensor RH
	rh = (vout/vdd - 0.16f) / 0.0062f;
	
	// Temperature compensation
	rh = rh / (1.0546f - 0.00216f * temperature);
	return rh;
}