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Try to read a temperature and humidity sensor (SI7020) using I2C on the ESP32
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Linaa
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November 13, 2017 - 3:27 am
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I am trying to read a temperature and humidity sensor (SI7020:http://www.kynix.com/Parts/2489506/SI7020-A10-GM.html) using I2C on the ESP32.

I modified their example code to read just from one slave device (0x40) but some commands do not work. I tried resetting the device with 0xFE as well.

I can read the device ID (0xFA):

*******************
TASK[0] MASTER READ SENSOR( SI7020 )
*******************
data_h: 48
data_l: 52
sensor val: 15428.333333

Image Enlarger

However if I try and read the temperature (0xE3), I get:

data_h: 00
data_l: 00

Image Enlarger

If I use 0xE0 I always get:

data_h: 39
data_l: 9f

Why am I not able to read the temperature from SI7020?

The code I'm using:

#include <stdio.h>
#include "driver/i2c.h"

 

#define DATA_LENGTH 512 /*!<Data buffer length for test buffer*/
#define RW_TEST_LENGTH 127 /*!<Data length for r/w test, any value from 0-DATA_LENGTH*/
#define DELAY_TIME_BETWEEN_ITEMS_MS 2000 /*!< delay time between different test items */

#define I2C_EXAMPLE_MASTER_SCL_IO 19 /*!< gpio number for I2C master clock */
#define I2C_EXAMPLE_MASTER_SDA_IO 18 /*!< gpio number for I2C master data */
#define I2C_EXAMPLE_MASTER_NUM I2C_NUM_1 /*!< I2C port number for master dev */
#define I2C_EXAMPLE_MASTER_TX_BUF_DISABLE 0 /*!< I2C master do not need buffer */
#define I2C_EXAMPLE_MASTER_RX_BUF_DISABLE 0 /*!< I2C master do not need buffer */
#define I2C_EXAMPLE_MASTER_FREQ_HZ 100000 /*!< I2C master clock frequency */

#define SI7020_SENSOR_ADDR 0x40 /*!< slave address for SI7020 sensor */
#define SI7020_CMD_READ 0xE0 /*!< Command to set measure mode */
//#define ESP_SLAVE_ADDR 0x28 /*!< ESP32 slave address, you can set any 7bit value */
#define WRITE_BIT I2C_MASTER_WRITE /*!< I2C master write */
#define READ_BIT I2C_MASTER_READ /*!< I2C master read */
#define ACK_CHECK_EN 0x1 /*!< I2C master will check ack from slave*/
#define ACK_CHECK_DIS 0x0 /*!< I2C master will not check ack from slave */
#define ACK_VAL 0x0 /*!< I2C ack value */
#define NACK_VAL 0x1 /*!< I2C nack value */

xSemaphoreHandle print_mux;

/**
* @brief test code to write esp-i2c-slave
*
* 1. set mode
* _________________________________________________________________
* | start | slave_addr + wr_bit + ack | write 1 byte + ack | stop |
* --------|---------------------------|---------------------|------|
* 2. wait more than 24 ms
* 3. read data
* ______________________________________________________________________________________
* | start | slave_addr + rd_bit + ack | read 1 byte + ack | read 1 byte + nack | stop |
* --------|---------------------------|--------------------|--------------------|------|
*/
static esp_err_t i2c_example_master_sensor_test(i2c_port_t i2c_num, uint8_t* data_h, uint8_t* data_l)
{
i2c_cmd_handle_t cmd = i2c_cmd_link_create();
i2c_master_start(cmd);
i2c_master_write_byte(cmd, SI7020_SENSOR_ADDR << 1 | WRITE_BIT, ACK_CHECK_DIS);
i2c_master_write_byte(cmd, SI7020_CMD_READ, ACK_CHECK_EN);
i2c_master_stop(cmd);
int ret = i2c_master_cmd_begin(i2c_num, cmd, 1000 / portTICK_RATE_MS);
i2c_cmd_link_delete(cmd);
if (ret == ESP_FAIL) {
return ret;
}
vTaskDelay(1000 / portTICK_RATE_MS);

cmd = i2c_cmd_link_create();
i2c_master_start(cmd);
i2c_master_write_byte(cmd, SI7020_SENSOR_ADDR << 1 | READ_BIT, ACK_CHECK_DIS);
i2c_master_read_byte(cmd, data_h, ACK_VAL);
i2c_master_read_byte(cmd, data_l, NACK_VAL);
i2c_master_stop(cmd);
ret = i2c_master_cmd_begin(i2c_num, cmd, 1000 / portTICK_RATE_MS);
i2c_cmd_link_delete(cmd);
if (ret == ESP_FAIL) {
return ESP_FAIL;
}
return ESP_OK;
}

/**
* @brief i2c master initialization
*/
static void i2c_example_master_init()
{
int i2c_master_port = I2C_EXAMPLE_MASTER_NUM;
i2c_config_t conf;
conf.mode = I2C_MODE_MASTER;
conf.sda_io_num = I2C_EXAMPLE_MASTER_SDA_IO;
conf.sda_pullup_en = GPIO_PULLUP_ENABLE;
conf.scl_io_num = I2C_EXAMPLE_MASTER_SCL_IO;
conf.scl_pullup_en = GPIO_PULLUP_ENABLE;
conf.master.clk_speed = I2C_EXAMPLE_MASTER_FREQ_HZ;
i2c_param_config(i2c_master_port, &conf);
i2c_driver_install(i2c_master_port, conf.mode,
I2C_EXAMPLE_MASTER_RX_BUF_DISABLE,
I2C_EXAMPLE_MASTER_TX_BUF_DISABLE, 0);
}

static void i2c_test_task(void* arg)
{
int i = 0;
int ret;
uint32_t task_idx = (uint32_t) arg;
uint8_t* data = (uint8_t*) malloc(DATA_LENGTH);
uint8_t sensor_data_h, sensor_data_l;

while (1) {
ret = i2c_example_master_sensor_test( I2C_EXAMPLE_MASTER_NUM, &sensor_data_h, &sensor_data_l);
xSemaphoreTake(print_mux, portMAX_DELAY);
printf("*******************
");
printf("TASK[%d] MASTER READ SENSOR( SI7020 )
", task_idx);
printf("*******************
");
if (ret == ESP_OK) {
printf("data_h: %02x
", sensor_data_h);
printf("data_l: %02x
", sensor_data_l);
printf("sensor val: %f
", ( sensor_data_h << 8 | sensor_data_l ) / 1.2);
} else {
printf("No ack, sensor not connected...skip...
");
}
xSemaphoreGive(print_mux);
vTaskDelay(( DELAY_TIME_BETWEEN_ITEMS_MS * ( task_idx + 1 ) ) / portTICK_RATE_MS);

//---------------------------------------------------
for (i = 0; i < DATA_LENGTH; i++) {
data[i] = i;
}
}
}

void app_main()
{
print_mux = xSemaphoreCreateMutex();
//i2c_example_slave_init();
i2c_example_master_init();

xTaskCreate(i2c_test_task, "i2c_test_task_0", 1024 * 2, (void* ) 0, 10, NULL);
//xTaskCreate(i2c_test_task, "i2c_test_task_1", 1024 * 2, (void* ) 1, 10, NULL);
}

 

Can anyone help me out?Thanks!

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