grove: add light sensor

Add driver for the Grove Light Sensor which detects changes in ambient light.

Sensor reference page:
	http://www.seeedstudio.com/wiki/Grove_-_Light_Sensor

Origin: Original
Change-Id: I88ae20cc9faa8ab8f274b0bd7a114db5c1a87a91
Signed-off-by: Bogdan Davidoaia <bogdan.m.davidoaia@intel.com>

3 files changed, 146 insertions, 0 deletions

diff --git a/drivers/grove/Kconfig b/drivers/grove/Kconfig
index a544b2aa4..3a99865c1 100644
--- a/drivers/grove/Kconfig
+++ b/drivers/grove/Kconfig
@@ -66,3 +66,48 @@ config GROVE_LCD_RGB_INIT_PRIORITY
 	  Device driver initialization priority.
 	  As the device is connected to I2C bus, its driver has
 	  to be initialized after the I2C one.
+
+config GROVE_LIGHT_SENSOR
+	bool
+	prompt "Enable the Seeed Grove Light Sensor"
+	depends on GROVE && ADC && NEWLIB_LIBC
+	default n
+	help
+	  Setting this value will enable dirver support for the Grove Light
+	  Sensor.
+
+config GROVE_LIGHT_SENSOR_NAME
+	string
+	prompt "Driver name"
+	depends on GROVE_LIGHT_SENSOR
+	default "GROVE_LIGHT_SENSOR"
+	help
+	  Specify the device name with which the sensor is identified.
+
+config GROVE_LIGHT_SENSOR_ADC_DEV_NAME
+	string
+	prompt "ADC where Grove Light Sensor is connected"
+	depends on GROVE_LIGHT_SENSOR
+	default "ADC_0"
+	help
+	  Specify the device name of the ADC to which the Grove Light Sensor
+	  is connected.
+
+config GROVE_LIGHT_SENSOR_ADC_CHANNEL
+	int
+	prompt "ADC channel used by Grove Light Sensor"
+	depends on GROVE_LIGHT_SENSOR
+	default 10
+	help
+	  Specify the channel of the ADC to which the Grove Light Sensor is
+	  connected.
+
+config GROVE_LIGHT_SENSOR_INIT_PRIORITY
+	int
+	prompt "Init priority"
+	default 70
+	depends on GROVE_LIGHT_SENSOR
+	help
+	  Device driver initialization priority.
+	  As the device is connected to an ADC device, its driver has to be
+	  initialized after the ADC device.
diff --git a/drivers/grove/Makefile b/drivers/grove/Makefile
index 499e25753..cafde1859 100644
--- a/drivers/grove/Makefile
+++ b/drivers/grove/Makefile
@@ -1 +1,2 @@
 obj-$(CONFIG_GROVE_LCD_RGB) += lcd_rgb.o
+obj-$(CONFIG_GROVE_LIGHT_SENSOR) += light_sensor.o
diff --git a/drivers/grove/light_sensor.c b/drivers/grove/light_sensor.c
new file mode 100644
index 000000000..92ba181a5
--- /dev/null
+++ b/drivers/grove/light_sensor.c
@@ -0,0 +1,100 @@
+/*
+ * Copyright (c) 2016 Intel Corporation
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#include <adc.h>
+#include <device.h>
+#include <math.h>
+#include <sensor.h>
+#include <zephyr.h>
+
+#define SYS_LOG_DOMAIN "GROVE_LIGHT_SENSOR"
+#define SYS_LOG_LEVEL CONFIG_GROVE_SYS_LOG_LEVEL
+#include <misc/sys_log.h>
+
+struct gls_data {
+	struct device *adc;
+	struct adc_seq_entry sample;
+	struct adc_seq_table adc_table;
+	uint8_t adc_buffer[4];
+};
+
+static int gls_sample_fetch(struct device *dev, enum sensor_channel chan)
+{
+	struct gls_data *drv_data = dev->driver_data;
+
+	return adc_read(drv_data->adc, &drv_data->adc_table);
+}
+
+static int gls_channel_get(struct device *dev,
+			   enum sensor_channel chan,
+			   struct sensor_value *val)
+{
+	struct gls_data *drv_data = dev->driver_data;
+	uint16_t analog_val;
+	double ldr_val;
+
+	/* rescale sample from 12bit (Zephyr) to 10bit (Grove) */
+	analog_val = ((uint16_t)drv_data->adc_buffer[1] << 8) |
+		     drv_data->adc_buffer[0];
+	analog_val = analog_val >> 2;
+
+	/*
+	 * The formula for converting the analog value to lux is taken from
+	 * the UPM project:
+	 *     https://github.com/intel-iot-devkit/upm/blob/master/src/grove/grove.cxx#L161
+	 */
+	ldr_val = (1023.0 - analog_val) * 10.0 / analog_val;
+	val->type = SENSOR_VALUE_TYPE_DOUBLE;
+	val->dval = 10000.0 / pow(ldr_val * 15.0, 4.0/3.0);
+
+	return 0;
+}
+
+static struct sensor_driver_api gls_api = {
+	.sample_fetch = &gls_sample_fetch,
+	.channel_get = &gls_channel_get,
+};
+
+static int gls_init(struct device *dev)
+{
+	struct gls_data *drv_data = dev->driver_data;
+
+	drv_data->adc =
+		device_get_binding(CONFIG_GROVE_LIGHT_SENSOR_ADC_DEV_NAME);
+	if (drv_data->adc == NULL) {
+		SYS_LOG_ERR("Failed to get ADC device.");
+		return -EINVAL;
+	}
+
+	drv_data->sample.sampling_delay = 12;
+	drv_data->sample.channel_id = CONFIG_GROVE_LIGHT_SENSOR_ADC_CHANNEL;
+	drv_data->sample.buffer = drv_data->adc_buffer;
+	drv_data->sample.buffer_length = 4;
+
+	drv_data->adc_table.entries = &drv_data->sample;
+	drv_data->adc_table.num_entries = 1;
+
+	adc_enable(drv_data->adc);
+
+	dev->driver_api = &gls_api;
+
+	return 0;
+}
+
+struct gls_data gls_data;
+
+DEVICE_INIT(gls_dev, CONFIG_GROVE_LIGHT_SENSOR_NAME, &gls_init, &gls_data,
+	    NULL, SECONDARY, CONFIG_GROVE_LIGHT_SENSOR_INIT_PRIORITY);