Driver for Bosch Sensortec BME680 added (#469)

* Driver for Bosch Sensortec BME680 added

examples/bme680/bme680_one_sensor/Makefile

@@ -0,0 +1,3 @@
+PROGRAM=BME680_One_Sensor
+EXTRA_COMPONENTS = extras/i2c extras/bme680
+include ../../../common.mk

examples/bme680/bme680_one_sensor/bme680_one_sensor.c

@@ -0,0 +1,131 @@
+/**
+ * Simple example with one sensor connected either to I2C bus 0 or
+ * SPI bus 1.
+ *
+ * Harware configuration:
+ *
+ *   I2C   +-------------------------+     +----------+
+ *         | ESP8266  Bus 0          |     | BME680   |
+ *         |          GPIO 5 (SCL)   ------> SCL      |
+ *         |          GPIO 4 (SDA)   ------- SDA      |
+ *         +-------------------------+     +----------+
+ *
+ *   SPI   +-------------------------+     +----------+
+ *         | ESP8266  Bus 1          |     | BME680   |
+ *         |          GPIO 12 (MISO) <-----< SDO      |
+ *         |          GPIO 13 (MOSI) >-----> SDI      |
+ *         |          GPIO 14 (SCK)  >-----> SCK      |
+ *         |          GPIO 2  (CS)   >-----> CS       |
+ *         +-------------------------+     +----------+
+ */
+
+// Uncomment to use SPI
+// #define SPI_USED
+
+#include "espressif/esp_common.h"
+#include "esp/uart.h"
+
+#include "FreeRTOS.h"
+#include "task.h"
+
+// include communication interface driver
+#include "esp/spi.h"
+#include "i2c/i2c.h"
+
+// include BME680 driver
+#include "bme680/bme680.h"
+
+
+#ifdef SPI_USED
+// define SPI interface for BME680 sensors
+#define SPI_BUS         1
+#define SPI_CS_GPIO     2   // GPIO 15, the default CS of SPI bus 1, can't be used
+#else
+// define I2C interface for BME680 sensors
+#define I2C_BUS         0
+#define I2C_SCL_PIN     5
+#define I2C_SDA_PIN     4
+#endif
+
+static bme680_sensor_t* sensor;
+
+/*
+ * User task that triggers measurements of sensor every seconds. It uses
+ * function *vTaskDelay* to wait for measurement results. Busy wating
+ * alternative is shown in comments
+ */
+void user_task(void *pvParameters)
+{
+    bme680_values_float_t values;
+
+    TickType_t last_wakeup = xTaskGetTickCount();
+
+    // as long as sensor configuration isn't changed, duration is constant
+    uint32_t duration = bme680_get_measurement_duration(sensor);
+
+    while (1)
+    {
+        // trigger the sensor to start one TPHG measurement cycle
+        if (bme680_force_measurement (sensor))
+        {
+            // passive waiting until measurement results are available
+            vTaskDelay (duration);
+
+            // alternatively: busy waiting until measurement results are available
+            // while (bme680_is_measuring (sensor)) ;
+
+            // get the results and do something with them
+            if (bme680_get_results_float (sensor, &values))
+                printf("%.3f BME680 Sensor: %.2f °C, %.2f %%, %.2f hPa, %.2f Ohm\n",
+                       (double)sdk_system_get_time()*1e-3,
+                       values.temperature, values.humidity,
+                       values.pressure, values.gas_resistance);
+        }
+        // passive waiting until 1 second is over
+        vTaskDelayUntil(&last_wakeup, 1000 / portTICK_PERIOD_MS);
+    }
+}
+
+
+void user_init(void)
+{
+    // Set UART Parameter
+    uart_set_baud(0, 115200);
+    // Give the UART some time to settle
+    sdk_os_delay_us(500);
+
+    /** -- MANDATORY PART -- */
+
+    #ifdef SPI_USED
+    // Init the sensor connected either to SPI.
+    sensor = bme680_init_sensor (SPI_BUS, 0, SPI_CS_GPIO);
+    #else
+    // Init all I2C bus interfaces at which BME680 sensors are connected
+    i2c_init(I2C_BUS, I2C_SCL_PIN, I2C_SDA_PIN, I2C_FREQ_100K);
+
+    // Init the sensor connected either to I2C.
+    sensor = bme680_init_sensor (I2C_BUS, BME680_I2C_ADDRESS_2, 0);
+    #endif
+
+    if (sensor)
+    {
+        // Create a task that uses the sensor
+        xTaskCreate(user_task, "user_task", 256, NULL, 2, NULL);
+
+        /** -- OPTIONAL PART -- */
+
+        // Changes the oversampling rates to 4x oversampling for temperature
+        // and 2x oversampling for humidity. Pressure measurement is skipped.
+        bme680_set_oversampling_rates(sensor, osr_4x, osr_none, osr_2x);
+
+        // Change the IIR filter size for temperature and pressure to 7.
+        bme680_set_filter_size(sensor, iir_size_7);
+
+        // Change the heater profile 0 to 200 degree Celcius for 100 ms.
+        bme680_set_heater_profile (sensor, 0, 200, 100);
+        bme680_use_heater_profile (sensor, 0);
+
+        // Set ambient temperature to 10 degree Celsius
+        bme680_set_ambient_temperature (sensor, 10);
+    }
+}