app: add fetching data from bme280 sensor

- Remove example_sensor node and add BME280 sensor to nrf9160dk_nrf9160.overlay with correct I2C2 pinctrl and address
- Enable logging in prj.conf
- Update main.c to use BME280 sensor, fetch and log temperature, pressure, and humidity
- Remove unused variables and legacy proximity logic

Refs: #4

Signed-off-by: Natalia Pluta <pluta.natalia.m@gmail.com>

Author: nmpluta

app/boards/nrf9160dk_nrf9160.overlay

@@ -3,12 +3,36 @@
  * SPDX-License-Identifier: Apache-2.0
  */
 
-/ {
-	example_sensor: example-sensor {
-		compatible = "zephyr,example-sensor";
-		input-gpios = <&gpio0 11 (GPIO_PULL_UP | GPIO_ACTIVE_LOW)>;
+&pinctrl {
+	i2c2_default_alt: i2c2_default_alt {
+		group1 {
+			psels = <NRF_PSEL(TWIM_SDA, 0, 30)>,
+					<NRF_PSEL(TWIM_SCL, 0, 31)>;
+		};
+	};
+
+	i2c2_sleep_alt: i2c2_sleep_alt {
+		group1 {
+			psels = <NRF_PSEL(TWIM_SDA, 0, 30)>,
+					<NRF_PSEL(TWIM_SCL, 0, 31)>;
+			low-power-enable;
+		};
+	};
+};
+
+&i2c2 {
+	status = "okay";
+	pinctrl-0 = <&i2c2_default_alt>;
+	pinctrl-1 = <&i2c2_sleep_alt>;
+	pinctrl-names = "default", "sleep";
+	bme280: bme280@77 {
+		compatible = "bosch,bme280";
+		reg = <0x77>;
+		status = "okay";
 	};
+};
 
+/ {
 	blink_led: blink-led {
 		compatible = "blink-gpio-led";
 		led-gpios = <&gpio0 5 GPIO_ACTIVE_HIGH>; // Green LED 4 on the nRF9160 DK

app/prj.conf

@@ -3,5 +3,11 @@
 #
 # This file contains selected Kconfig options for the application.
 
+CONFIG_LOG=y
 CONFIG_SENSOR=y
 CONFIG_BLINK=y
+
+# Enable I2C and sensor subsystem for BME280
+CONFIG_I2C=y
+CONFIG_SENSOR=y
+CONFIG_BME280=y

app/src/main.c

@@ -19,15 +19,13 @@ LOG_MODULE_REGISTER(main, CONFIG_APP_LOG_LEVEL);
 int main(void)
 {
 	int ret;
-	unsigned int period_ms = BLINK_PERIOD_MS_MAX;
 	const struct device *sensor, *blink;
-	struct sensor_value last_val = {0}, val;
 
-	printk("Zephyr Fire Detection System %s\n", APP_VERSION_STRING);
+	LOG_INF("Zephyr Fire Detection System %s", APP_VERSION_STRING);
 
-	sensor = DEVICE_DT_GET(DT_NODELABEL(example_sensor));
+	sensor = DEVICE_DT_GET(DT_NODELABEL(bme280));
 	if (!device_is_ready(sensor)) {
-		LOG_ERR("Sensor not ready");
+		LOG_ERR("BME280 sensor not ready");
 		return 0;
 	}
 
@@ -43,35 +41,38 @@ int main(void)
 		return 0;
 	}
 
-	printk("Use the sensor to change LED blinking period\n");
-
 	while (1) {
 		ret = sensor_sample_fetch(sensor);
 		if (ret < 0) {
-			LOG_ERR("Could not fetch sample (%d)", ret);
-			return 0;
+			LOG_ERR("Could not fetch BME280 sample (%d)", ret);
+			k_sleep(K_MSEC(1000));
+			continue;
 		}
 
-		ret = sensor_channel_get(sensor, SENSOR_CHAN_PROX, &val);
+		struct sensor_value temp, press, hum;
+
+		ret = sensor_channel_get(sensor, SENSOR_CHAN_AMBIENT_TEMP, &temp);
 		if (ret < 0) {
-			LOG_ERR("Could not get sample (%d)", ret);
-			return 0;
+			LOG_ERR("Could not get temperature (%d)", ret);
+			continue;
 		}
 
-		if ((last_val.val1 == 0) && (val.val1 == 1)) {
-			if (period_ms == 0U) {
-				period_ms = BLINK_PERIOD_MS_MAX;
-			} else {
-				period_ms -= BLINK_PERIOD_MS_STEP;
-			}
+		ret = sensor_channel_get(sensor, SENSOR_CHAN_PRESS, &press);
+		if (ret < 0) {
+			LOG_ERR("Could not get pressure (%d)", ret);
+			continue;
+		}
 
-			printk("Proximity detected, setting LED period to %u ms\n", period_ms);
-			blink_set_period_ms(blink, period_ms);
+		ret = sensor_channel_get(sensor, SENSOR_CHAN_HUMIDITY, &hum);
+		if (ret < 0) {
+			LOG_ERR("Could not get humidity (%d)", ret);
+			continue;
 		}
 
-		last_val = val;
+		LOG_INF("BME280: Temp: %d.%02d C, Press: %d.%02d kPa, Hum: %d.%02d %%", temp.val1,
+			temp.val2, press.val1, press.val2, hum.val1, hum.val2);
 
-		k_sleep(K_MSEC(100));
+		k_sleep(K_MSEC(1000));
 	}
 
 	return 0;