87 lines
4.1 KiB
C
87 lines
4.1 KiB
C
/** library to communicate with MLX90614 infra-red thermometer
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* @file
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* @author King Kévin <kingkevin@cuvoodoo.info>
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* @copyright SPDX-License-Identifier: GPL-3.0-or-later
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* @date 2020
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* @note peripherals used: GPIO @ref sensor_mlx90614_gpio, I2C @ref i2c_master_i2c
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* @note this library only uses the I²C interface, not the PWM output
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*/
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/* standard libraries */
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#include <stdint.h> // standard integer types
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#include <stdbool.h> // boolean type
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#include <stdlib.h> // general utilities
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#include <math.h> // NaN definition
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/* STM32 (including CM3) libraries */
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#include <libopencm3/stm32/rcc.h> // real-time control clock library
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#include <libopencm3/stm32/gpio.h> // general purpose input output library
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#include <libopencm3/stm32/i2c.h> // I²C library
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/* own libraries */
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#include "global.h" // global utilities
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#include "sensor_mlx90614.h" // own definitions
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#include "smbus_master.h" // SMBus utilities
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/** @defgroup sensor_mlx90614_gpio GPIO pin used to control the MLX90614
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* @{
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*/
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#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) */
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/** @} */
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/** MLX90614 I²C slave address */
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static uint8_t sensor_mlx90614_slave_addr = 0x5a;
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bool sensor_mlx90614_setup(uint8_t slave_addr)
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{
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if (!smbus_master_check_signals()) { // check if there are pull-ups to operate I²C
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return false;
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}
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// send request condition to switch to I²C mode
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rcc_periph_clock_enable(GPIO_RCC(SENSOR_MLX90614_SCL)); // enable clock for GPIO port domain
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gpio_mode_setup(GPIO_PORT(SENSOR_MLX90614_SCL), GPIO_MODE_OUTPUT, GPIO_PUPD_NONE, GPIO_PIN(SENSOR_MLX90614_SCL)); // set pin as output
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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
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gpio_clear(GPIO_PORT(SENSOR_MLX90614_SCL), GPIO_PIN(SENSOR_MLX90614_SCL)); // set low to send request condition
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sleep_us(1024 + 500); // SMBus Request is min. 1.024 ms
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gpio_set(GPIO_PORT(SENSOR_MLX90614_SCL), GPIO_PIN(SENSOR_MLX90614_SCL)); // set back high to end request condition
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if (slave_addr < 0x80) { // only the least 7-bit are valid (use default address else)
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sensor_mlx90614_slave_addr = slave_addr; // save I²C slave address of MLX90614
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}
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smbus_master_setup(100, true); // setup SMBus with PEC
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uint8_t response[2]; // response is always 2 bytes
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// test if the device is present
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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
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const enum smbus_master_rc rc = smbus_master_command_read(sensor_mlx90614_slave_addr, 0x20 | 0x0e, response, LENGTH(response)); // read its own slave address
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if (SMBUS_MASTER_RC_NONE != rc) { // read failed
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return false; // could not read from SMBus device
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}
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if (sensor_mlx90614_slave_addr != response[0]) { // the used slave address does not match the one in the ROM
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return false; // this is probably not a MLX90614
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}
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return true;
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}
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float sensor_mlx90614_temperature_ambient(void)
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{
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uint8_t response[2]; // response is always 2 bytes
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const enum smbus_master_rc rc = smbus_master_command_read(sensor_mlx90614_slave_addr, 0x00 | 0x06, response, LENGTH(response)); // read Ta from RAM
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if (SMBUS_MASTER_RC_NONE != rc) { // read failed
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return NAN;
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}
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const uint16_t temp = response[0] + (response[1] << 8); // low byte is transferred first
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return temp * 0.02 - 273.15; // calculated temperature according to specification 7.7.1
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}
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float sensor_mlx90614_temperature_object(void)
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{
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uint8_t response[2]; // response is always 2 bytes
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const enum smbus_master_rc rc = smbus_master_command_read(sensor_mlx90614_slave_addr, 0x00 | 0x07, response, LENGTH(response)); // read Tobj1 from RAM
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if (SMBUS_MASTER_RC_NONE != rc) { // read failed
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return NAN;
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}
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const uint16_t temp = response[0] + (response[1] << 8); // low byte is transferred first
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return temp * 0.02 - 273.15; // calculated temperature according to specification 7.7.1
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}
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