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‎component.mk

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#
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# Component Makefile
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#
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COMPONENT_SRCDIRS := .
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COMPONENT_ADD_INCLUDEDIRS := .
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COMPONENT_PRIV_INCLUDEDIRS :=

‎htu21d.c

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/*
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* HTU21D Component
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*
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* esp-idf component to interface with HTU21D humidity and temperature sensor
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* by TE Connectivity (http://www.te.com/usa-en/product-CAT-HSC0004.html)
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*
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* Luca Dentella, www.lucadentella.it
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*/
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// Component header file
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#include "htu21d.h"
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int htu21d_init(i2c_port_t port, int sda_pin, int scl_pin, gpio_pullup_t sda_internal_pullup, gpio_pullup_t scl_internal_pullup) {
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esp_err_t ret;
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_port = port;
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// setup i2c controller
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i2c_config_t conf;
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conf.mode = I2C_MODE_MASTER;
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conf.sda_io_num = sda_pin;
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conf.scl_io_num = scl_pin;
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conf.sda_pullup_en = sda_internal_pullup;
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conf.scl_pullup_en = scl_internal_pullup;
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conf.master.clk_speed = 100000;
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ret = i2c_param_config(port, &conf);
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if(ret != ESP_OK) return HTU21D_ERR_CONFIG;
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// install the driver
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ret = i2c_driver_install(port, I2C_MODE_MASTER, 0, 0, 0);
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if(ret != ESP_OK) return HTU21D_ERR_INSTALL;
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// verify if a sensor is present
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i2c_cmd_handle_t cmd = i2c_cmd_link_create();
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i2c_master_start(cmd);
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i2c_master_write_byte(cmd, (HTU21D_ADDR << 1) | I2C_MASTER_WRITE, true);
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i2c_master_stop(cmd);
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if(i2c_master_cmd_begin(port, cmd, 1000 / portTICK_RATE_MS) != ESP_OK)
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return HTU21D_ERR_NOTFOUND;
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return HTU21D_ERR_OK;
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}
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float ht21d_read_temperature() {
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// get the raw value from the sensor
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uint16_t raw_temperature = read_value(TRIGGER_TEMP_MEASURE_NOHOLD);
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if(raw_temperature == 0) return -999;
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// return the real value, formula in datasheet
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return (raw_temperature * 175.72 / 65536.0) - 46.85;
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}
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float ht21d_read_humidity() {
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// get the raw value from the sensor
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uint16_t raw_humidity = read_value(TRIGGER_HUMD_MEASURE_NOHOLD);
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if(raw_humidity == 0) return -999;
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// return the real value, formula in datasheet
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return (raw_humidity * 125.0 / 65536.0) - 6.0;
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}
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uint8_t ht21d_get_resolution() {
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uint8_t reg_value = ht21d_read_user_register();
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return reg_value & 0b10000001;
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}
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int ht21d_set_resolution(uint8_t resolution) {
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// get the actual resolution
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uint8_t reg_value = ht21d_read_user_register();
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reg_value &= 0b10000001;
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// update the register value with the new resolution
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resolution &= 0b10000001;
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reg_value |= resolution;
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return ht21d_write_user_register(reg_value);
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}
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int htu21d_soft_reset() {
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esp_err_t ret;
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// send the command
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i2c_cmd_handle_t cmd = i2c_cmd_link_create();
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i2c_master_start(cmd);
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i2c_master_write_byte(cmd, (HTU21D_ADDR << 1) | I2C_MASTER_WRITE, true);
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i2c_master_write_byte(cmd, SOFT_RESET, true);
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i2c_master_stop(cmd);
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ret = i2c_master_cmd_begin(_port, cmd, 1000 / portTICK_RATE_MS);
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i2c_cmd_link_delete(cmd);
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switch(ret) {
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case ESP_ERR_INVALID_ARG:
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return HTU21D_ERR_INVALID_ARG;
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case ESP_FAIL:
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return HTU21D_ERR_FAIL;
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case ESP_ERR_INVALID_STATE:
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return HTU21D_ERR_INVALID_STATE;
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case ESP_ERR_TIMEOUT:
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return HTU21D_ERR_TIMEOUT;
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}
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return HTU21D_ERR_OK;
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}
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uint8_t ht21d_read_user_register() {
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esp_err_t ret;
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// send the command
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i2c_cmd_handle_t cmd = i2c_cmd_link_create();
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i2c_master_start(cmd);
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i2c_master_write_byte(cmd, (HTU21D_ADDR << 1) | I2C_MASTER_WRITE, true);
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i2c_master_write_byte(cmd, READ_USER_REG, true);
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i2c_master_stop(cmd);
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ret = i2c_master_cmd_begin(_port, cmd, 1000 / portTICK_RATE_MS);
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i2c_cmd_link_delete(cmd);
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if(ret != ESP_OK) return 0;
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// receive the answer
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uint8_t reg_value;
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cmd = i2c_cmd_link_create();
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i2c_master_start(cmd);
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i2c_master_write_byte(cmd, (HTU21D_ADDR << 1) | I2C_MASTER_READ, true);
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i2c_master_read_byte(cmd, &reg_value, 0x01);
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i2c_master_stop(cmd);
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ret = i2c_master_cmd_begin(_port, cmd, 1000 / portTICK_RATE_MS);
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i2c_cmd_link_delete(cmd);
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if(ret != ESP_OK) return 0;
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return reg_value;
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}
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int ht21d_write_user_register(uint8_t value) {
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esp_err_t ret;
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// send the command
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i2c_cmd_handle_t cmd = i2c_cmd_link_create();
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i2c_master_start(cmd);
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i2c_master_write_byte(cmd, (HTU21D_ADDR << 1) | I2C_MASTER_WRITE, true);
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i2c_master_write_byte(cmd, WRITE_USER_REG, true);
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i2c_master_write_byte(cmd, value, true);
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i2c_master_stop(cmd);
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ret = i2c_master_cmd_begin(_port, cmd, 1000 / portTICK_RATE_MS);
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i2c_cmd_link_delete(cmd);
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switch(ret) {
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case ESP_ERR_INVALID_ARG:
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return HTU21D_ERR_INVALID_ARG;
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case ESP_FAIL:
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return HTU21D_ERR_FAIL;
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case ESP_ERR_INVALID_STATE:
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return HTU21D_ERR_INVALID_STATE;
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case ESP_ERR_TIMEOUT:
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return HTU21D_ERR_TIMEOUT;
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}
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return HTU21D_ERR_OK;
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}
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uint16_t read_value(uint8_t command) {
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esp_err_t ret;
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// send the command
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i2c_cmd_handle_t cmd = i2c_cmd_link_create();
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i2c_master_start(cmd);
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i2c_master_write_byte(cmd, (HTU21D_ADDR << 1) | I2C_MASTER_WRITE, true);
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i2c_master_write_byte(cmd, command, true);
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i2c_master_stop(cmd);
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ret = i2c_master_cmd_begin(_port, cmd, 1000 / portTICK_RATE_MS);
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i2c_cmd_link_delete(cmd);
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if(ret != ESP_OK) return 0;
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// wait for the sensor (50ms)
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vTaskDelay(50 / portTICK_RATE_MS);
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// receive the answer
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uint8_t msb, lsb, crc;
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cmd = i2c_cmd_link_create();
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i2c_master_start(cmd);
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i2c_master_write_byte(cmd, (HTU21D_ADDR << 1) | I2C_MASTER_READ, true);
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i2c_master_read_byte(cmd, &msb, 0x00);
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i2c_master_read_byte(cmd, &lsb, 0x00);
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i2c_master_read_byte(cmd, &crc, 0x01);
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i2c_master_stop(cmd);
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ret = i2c_master_cmd_begin(_port, cmd, 1000 / portTICK_RATE_MS);
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i2c_cmd_link_delete(cmd);
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if(ret != ESP_OK) return 0;
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uint16_t raw_value = ((uint16_t) msb << 8) | (uint16_t) lsb;
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if(!is_crc_valid(raw_value, crc)) printf("CRC invalid\r\n");
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return raw_value & 0xFFFC;
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}
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// verify the CRC, algorithm in the datasheet (see comments below)
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bool is_crc_valid(uint16_t value, uint8_t crc) {
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// line the bits representing the input in a row (first data, then crc)
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uint32_t row = (uint32_t)value << 8;
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row |= crc;
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// polynomial = x^8 + x^5 + x^4 + 1
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// padded with zeroes corresponding to the bit length of the CRC
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uint32_t divisor = (uint32_t)0x988000;
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for (int i = 0 ; i < 16 ; i++) {
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// if the input bit above the leftmost divisor bit is 1,
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// the divisor is XORed into the input
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if (row & (uint32_t)1 << (23 - i)) row ^= divisor;
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// the divisor is then shifted one bit to the right
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divisor >>= 1;
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}
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// the remainder should equal zero if there are no detectable errors
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return (row == 0);
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}
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‎htu21d.h

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/*
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* HTU21D Component
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*
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* esp-idf component to interface with HTU21D humidity and temperature sensor
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* by TE Connectivity (http://www.te.com/usa-en/product-CAT-HSC0004.html)
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*
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* Luca Dentella, www.lucadentella.it
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*/
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// Error library
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#include "esp_err.h"
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// I2C driver
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#include "driver/i2c.h"
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// FreeRTOS (for delay)
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#include "freertos/task.h"
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#ifndef __ESP_HTU21D_H__
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#define __ESP_HTU21D_H__
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// sensor address
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#define HTU21D_ADDR 0x40
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// HTU21D commands
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#define TRIGGER_TEMP_MEASURE_HOLD 0xE3
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#define TRIGGER_HUMD_MEASURE_HOLD 0xE5
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#define TRIGGER_TEMP_MEASURE_NOHOLD 0xF3
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#define TRIGGER_HUMD_MEASURE_NOHOLD 0xF5
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#define WRITE_USER_REG 0xE6
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#define READ_USER_REG 0xE7
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#define SOFT_RESET 0xFE
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// return values
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#define HTU21D_ERR_OK 0x00
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#define HTU21D_ERR_CONFIG 0x01
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#define HTU21D_ERR_INSTALL 0x02
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#define HTU21D_ERR_NOTFOUND 0x03
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#define HTU21D_ERR_INVALID_ARG 0x04
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#define HTU21D_ERR_FAIL 0x05
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#define HTU21D_ERR_INVALID_STATE 0x06
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#define HTU21D_ERR_TIMEOUT 0x07
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// variables
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i2c_port_t _port;
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// functions
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int htu21d_init(i2c_port_t port, int sda_pin, int scl_pin, gpio_pullup_t sda_internal_pullup, gpio_pullup_t scl_internal_pullup);
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float ht21d_read_temperature();
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float ht21d_read_humidity();
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uint8_t ht21d_get_resolution();
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int ht21d_set_resolution(uint8_t resolution);
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int htu21d_soft_reset();
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// helper functions
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uint8_t ht21d_read_user_register();
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int ht21d_write_user_register(uint8_t value);
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uint16_t read_value(uint8_t command);
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bool is_crc_valid(uint16_t value, uint8_t crc);
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#endif // __ESP_HTU21D_H__

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