131 lines
4 KiB
C
131 lines
4 KiB
C
/**
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* Simple example with one sensor connected to I2C bus 0. It demonstrates
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* how to use CCS811 with an external NTC thermistor to determine ambient
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* temperature.
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*
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* Harware configuration:
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*
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* +------------------------+ +--------+
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* | ESP8266 Bus 0 | | CCS811 |
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* | GPIO 14 (SCL) >----> SCL |
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* | GPIO 13 (SDA) <----> SDA |
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* | GND -----> /WAKE |
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* +------------------------+ +--------+
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*/
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#include "espressif/esp_common.h"
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#include "esp/uart.h"
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#include "i2c/i2c.h"
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#include "FreeRTOS.h"
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#include <task.h>
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#include <math.h>
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// include CCS811 driver
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#include "ccs811/ccs811.h"
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// define I2C interfaces at which CCS811 sensors can be connected
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#define I2C_BUS 0
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#define I2C_SCL_PIN 14
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#define I2C_SDA_PIN 13
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static ccs811_sensor_t* sensor;
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/*
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* In this example, user task fetches the sensor values every seconds.
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*/
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// parameters of the Adafruit CCS811 Air Quality Sensor Breakout
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#define CCS811_R_REF 100000
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#define CCS811_R_NTC 10000
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#define CCS811_R_NTC_TEMP 25
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#define CCS811_BCONSTANT 3380
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void user_task_periodic(void *pvParameters)
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{
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uint16_t tvoc;
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uint16_t eco2;
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TickType_t last_wakeup = xTaskGetTickCount();
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while (1)
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{
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// get environmental data from another sensor and set them
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// ccs811_set_environmental_data (sensor, 25.3, 47.8);
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// get the results and do something with them
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if (ccs811_get_results (sensor, &tvoc, &eco2, 0, 0))
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printf("%.3f CCS811 Sensor periodic: TVOC %d ppb, eCO2 %d ppm\n",
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(double)sdk_system_get_time()*1e-3, tvoc, eco2);
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// get NTC resistance
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uint32_t r_ntc = ccs811_get_ntc_resistance (sensor, CCS811_R_REF);
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// calculation of temperature from application note ams AN000372
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double ntc_temp;
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ntc_temp = log((double)r_ntc / CCS811_R_NTC); // 1
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ntc_temp /= CCS811_BCONSTANT; // 2
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ntc_temp += 1.0 / (CCS811_R_NTC_TEMP + 273.15); // 3
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ntc_temp = 1.0 / ntc_temp; // 4
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ntc_temp -= 273.15; // 5
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printf("%.3f CCS811 Sensor temperature: R_NTC %u Ohm, T %f °C\n",
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(double)sdk_system_get_time()*1e-3, r_ntc, ntc_temp);
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// passive waiting until 1 second is over
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vTaskDelayUntil(&last_wakeup, 1100 / portTICK_PERIOD_MS);
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}
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}
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void user_init(void)
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{
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// set UART Parameter
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uart_set_baud(0, 115200);
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// give the UART some time to settle
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sdk_os_delay_us(500);
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/** -- MANDATORY PART -- */
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// init all I2C bus interfaces at which CCS811 sensors are connected
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i2c_init(I2C_BUS, I2C_SCL_PIN, I2C_SDA_PIN, I2C_FREQ_100K);
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// longer clock stretching is required for CCS811
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i2c_set_clock_stretch (I2C_BUS, CCS811_I2C_CLOCK_STRETCH);
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// init the sensor with slave address CCS811_I2C_ADDRESS_1 connected I2C_BUS.
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sensor = ccs811_init_sensor (I2C_BUS, CCS811_I2C_ADDRESS_1);
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if (sensor)
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{
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#if defined(INT_DATA_RDY_USED) || defined(INT_THRESHOLD_USED)
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// create a task that is resumed by interrupt handler to use the sensor
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xTaskCreate(user_task_interrupt, "user_task_interrupt", 256, NULL, 2, &nINT_task);
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// set the GPIO and interrupt handler for *nINT* interrupt
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gpio_set_interrupt(INT_GPIO, GPIO_INTTYPE_EDGE_NEG, nINT_handler);
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#ifdef INT_DATA_RDY_USED
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// enable the data ready interrupt
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ccs811_enable_interrupt (sensor, true);
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#else
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// set threshold parameters and enable threshold interrupt mode
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ccs811_set_eco2_thresholds (sensor, 600, 1100, 40);
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#endif
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#else
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// create a periodic task that uses the sensor
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xTaskCreate(user_task_periodic, "user_task_periodic", 256, NULL, 2, NULL);
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#endif
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// start periodic measurement with one measurement per second
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ccs811_set_mode (sensor, ccs811_mode_1s);
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}
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}
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