/** library to communicate with MLX90614 infra-red thermometer
 *  @file
 *  @author King Kévin <kingkevin@cuvoodoo.info>
 *  @copyright SPDX-License-Identifier: GPL-3.0-or-later
 *  @date 2020
 *  @note peripherals used: GPIO @ref sensor_mlx90614_gpio, I2C @ref i2c_master_i2c
 *  @note this library only uses the I²C interface, not the PWM output
 */
/* standard libraries */
#include <stdint.h> // standard integer types
#include <stdbool.h> // boolean type
#include <stdlib.h> // general utilities
#include <math.h> // NaN definition

/* STM32 (including CM3) libraries */
#include <libopencm3/stm32/rcc.h> // real-time control clock library
#include <libopencm3/stm32/gpio.h> // general purpose input output library
#include <libopencm3/stm32/i2c.h> // I²C library

/* own libraries */
#include "global.h" // global utilities
#include "sensor_mlx90614.h" // own definitions
#include "smbus_master.h" // SMBus utilities

/** @defgroup sensor_mlx90614_gpio GPIO pin used to control the MLX90614
 *  @{
 */
#define SENSOR_MLX90614_SCL PA8 /**< GPIO pin for SMBus SCL, use to send request condition to switch mode from PWM to SMBus (must be the same as used for SMBus communication) */
/** @} */

/** MLX90614 I²C slave address */
static uint8_t sensor_mlx90614_slave_addr = 0x5a;

bool sensor_mlx90614_setup(uint8_t slave_addr)
{
	if (!smbus_master_check_signals()) { // check if there are pull-ups to operate I²C
		return false;
	}

	// send request condition to switch to I²C mode
	rcc_periph_clock_enable(GPIO_RCC(SENSOR_MLX90614_SCL)); // enable clock for GPIO port domain
	gpio_mode_setup(GPIO_PORT(SENSOR_MLX90614_SCL), GPIO_MODE_OUTPUT, GPIO_PUPD_NONE, GPIO_PIN(SENSOR_MLX90614_SCL)); // set pin as output
	gpio_set_output_options(GPIO_PORT(SENSOR_MLX90614_SCL), GPIO_OTYPE_OD, GPIO_OSPEED_2MHZ, GPIO_PIN(SENSOR_MLX90614_SCL)); // set pin output as open-drain (should be pulled up by external resistors required for I²C communication
	gpio_clear(GPIO_PORT(SENSOR_MLX90614_SCL), GPIO_PIN(SENSOR_MLX90614_SCL)); // set low to send request condition
	sleep_us(1024 + 500); // SMBus Request is min. 1.024 ms
	gpio_set(GPIO_PORT(SENSOR_MLX90614_SCL), GPIO_PIN(SENSOR_MLX90614_SCL)); // set back high to end request condition

	if (slave_addr < 0x80) { // only the least 7-bit are valid (use default address else)
		sensor_mlx90614_slave_addr = slave_addr; // save I²C slave address of MLX90614
	}
	smbus_master_setup(100, true); // setup SMBus with PEC
	uint8_t response[2]; // response is always 2 bytes
	// test if the device is present
	smbus_master_command_read(sensor_mlx90614_slave_addr, 0x20 | 0x0e, response, LENGTH(response)); // I don't know whey, but the PEC for the first transfer is erroneous, maybe because it has some old bits in the calculation buffer
	const enum smbus_master_rc rc = smbus_master_command_read(sensor_mlx90614_slave_addr, 0x20 | 0x0e, response, LENGTH(response)); // read its own slave address
	if (SMBUS_MASTER_RC_NONE != rc) { // read failed
		return false; // could not read from SMBus device
	}
	
	if (sensor_mlx90614_slave_addr != response[0]) { // the used slave address does not match the one in the ROM
		return false; // this is probably not a MLX90614
	}
	return true;
}

float sensor_mlx90614_temperature_ambient(void)
{
	uint8_t response[2]; // response is always 2 bytes
	const enum smbus_master_rc rc = smbus_master_command_read(sensor_mlx90614_slave_addr, 0x00 | 0x06, response, LENGTH(response)); // read Ta from RAM
	if (SMBUS_MASTER_RC_NONE != rc) { // read failed
		return NAN;
	}
	const uint16_t temp = response[0] + (response[1] << 8); // low byte is transferred first
	return temp * 0.02 - 273.15; // calculated temperature according to specification 7.7.1
}

float sensor_mlx90614_temperature_object(void)
{
	uint8_t response[2]; // response is always 2 bytes
	const enum smbus_master_rc rc = smbus_master_command_read(sensor_mlx90614_slave_addr, 0x00 | 0x07, response, LENGTH(response)); // read Tobj1 from RAM
	if (SMBUS_MASTER_RC_NONE != rc) { // read failed
		return NAN;
	}
	const uint16_t temp = response[0] + (response[1] << 8); // low byte is transferred first
	return temp * 0.02 - 273.15; // calculated temperature according to specification 7.7.1
}