sensors: Redefine SENSOR_CHAN_HUMIDITY in percents, not milli-percents.

Based on the discussion in #5693, the reason why humidity was defined
in milli-percent was likely following Linux which defines it as such
in its sensor subsystem:
http://elixir.free-electrons.com/linux/latest/source/Documentation/ABI/testing/sysfs-bus-iio#L263

However, Linux defines temperature in milli-degrees either, but
Zephyr uses degrees (similarly for most other quantities). Typical
sensor resolution/precision for humidity is also on the order of 1%.

One of the existing drivers, th02.c, already returned values in
percents, and few apps showed it without conversion and/or units,
leading to confusing output to user like "54500".

So, switching units to percents, and update all the drivers and
sample apps.

For few drivers, there was also optimized conversion arithmetics
to avoid u64_t operations. (There're probably more places to
optimize it, and temperature conversion could use such optimization
too, but that's left for another patch.)

Fixes: #5693

Signed-off-by: Paul Sokolovsky <paul.sokolovsky@linaro.org>

drivers/sensor/bme280/bme280.c

@@ -212,8 +212,6 @@ static int bme280_channel_get(struct device *dev,
 		 */
 		val->val1 = (data->comp_humidity >> 10);
 		val->val2 = (((data->comp_humidity & 0x3ff) * 1000 * 1000) >> 10);
-		val->val1 = val->val1 * 1000 + (val->val2 * 1000) / 1000000;
-		val->val2 = (val->val2 * 1000) % 1000000;
 		break;
 	default:
 		return -EINVAL;

drivers/sensor/dht/dht.c

@@ -168,7 +168,7 @@ static int dht_channel_get(struct device *dev,
 #if defined(CONFIG_DHT_CHIP_DHT11)
 	/* use only integral data byte */
 	if (chan == SENSOR_CHAN_HUMIDITY) {
-		val->val1 = drv_data->sample[0] * 1000;
+		val->val1 = drv_data->sample[0];
 		val->val2 = 0;
 	} else { /* chan == SENSOR_CHAN_TEMP */
 		val->val1 = drv_data->sample[2];
@@ -183,8 +183,8 @@ static int dht_channel_get(struct device *dev,
 
 	if (chan == SENSOR_CHAN_HUMIDITY) {
 		raw_val = (drv_data->sample[0] << 8) | drv_data->sample[1];
-		val->val1 = raw_val * 100;
-		val->val2 = 0;
+		val->val1 = raw_val / 10;
+		val->val2 = (raw_val % 10) * 100000;
 	} else { /* chan == SENSOR_CHAN_TEMP */
 		raw_val = (drv_data->sample[2] << 8) | drv_data->sample[3];
 

drivers/sensor/hdc1008/hdc1008.c

@@ -73,10 +73,12 @@ static int hdc1008_channel_get(struct device *dev,
 		val->val1 = (s32_t)(tmp >> 16) - 40;
 		val->val2 = (1000000 * (tmp & 0xFFFF)) >> 16;
 	} else if (chan == SENSOR_CHAN_HUMIDITY) {
-		/* val = 100000 * sample / 2^16 */
-		tmp = 100000 * (u64_t)drv_data->rh_sample;
-		val->val1 = tmp >> 16;
-		val->val2 = (1000000 * (tmp & 0xFFFF)) >> 16;
+		/* val = 100 * sample / 2^16 */
+		u32_t tmp2;
+		tmp2 = 100 * (u32_t)drv_data->rh_sample;
+		val->val1 = tmp2 >> 16;
+		/* x * 1000000 / 65536 == x * 15625 / 1024 */
+		val->val2 = (15625 * (tmp2 & 0xFFFF)) >> 10;
 	} else {
 		return -ENOTSUP;
 	}

drivers/sensor/hts221/hts221.c

@@ -43,9 +43,9 @@ static int hts221_channel_get(struct device *dev,
 			   (drv_data->h1_t0_out - drv_data->h0_t0_out) +
 			   drv_data->h0_rh_x2;
 
-		/* convert humidity x2 to mili-percent */
-		val->val1 = conv_val * 500;
-		val->val2 = 0;
+		/* convert humidity x2 to percent */
+		val->val1 = conv_val / 2;
+		val->val2 = (conv_val % 2) * 500000;
 	}
 
 	return 0;

drivers/sensor/sht3xd/sht3xd.c

@@ -126,10 +126,11 @@ static int sht3xd_channel_get(struct device *dev,
 		val->val1 = (s32_t)(tmp / 0xFFFF) - 45;
 		val->val2 = (1000000 * (tmp % 0xFFFF)) / 0xFFFF;
 	} else if (chan == SENSOR_CHAN_HUMIDITY) {
-		/* val = 100000 * sample / (2^16 -1) */
-		tmp = 100000 * (u64_t)drv_data->rh_sample;
-		val->val1 = tmp / 0xFFFF;
-		val->val2 = (1000000 * (tmp % 0xFFFF)) / 0xFFFF;
+		/* val = 100 * sample / (2^16 -1) */
+		u32_t tmp2 = 100 * (u32_t)drv_data->rh_sample;
+		val->val1 = tmp2 / 0xFFFF;
+		/* x * 100000 / 65536 == x * 15625 / 1024 */
+		val->val2 = (tmp2 % 0xFFFF) * 15625 / 1024;
 	} else {
 		return -ENOTSUP;
 	}

include/sensor.h

@@ -98,7 +98,7 @@ enum sensor_channel {
 	 * object is close.
 	 */
 	SENSOR_CHAN_PROX,
-	/** Humidity, in milli percent. */
+	/** Humidity, in percent. */
 	SENSOR_CHAN_HUMIDITY,
 	/** Illuminance in visible spectrum, in lux. */
 	SENSOR_CHAN_LIGHT,

samples/boards/arduino_101/environmental_sensing/ap/src/main.c

@@ -105,7 +105,7 @@ static void sensor_ipm_callback(void *context, u32_t id, volatile void *data)
 		break;
 	case SENSOR_CHAN_HUMIDITY:
 		/* resolution of 0.01 percent */
-		humidity_value = val->val1 / 10;
+		humidity_value = val->val1 * 100 + val->val2 / 10000;
 		break;
 	case SENSOR_CHAN_PRESS:
 		/* resolution of 0.1 Pa */

samples/boards/arduino_101/environmental_sensing/sensor/src/main.c

@@ -113,8 +113,7 @@ void main(void)
 
 		/* display himidity on LCD */
 		glcd_cursor_pos_set(glcd, 17 - strlen(row), 0);
-		sprintf(row, "RH:%d%c", val[1].val1/1000,
-			37 /* percent symbol */);
+		sprintf(row, "RH:%d%%", val[1].val1);
 		glcd_print(glcd, row, strlen(row));
 
 		/* display pressure on LCD */

samples/sensor/hts221/src/main.c

@@ -39,9 +39,9 @@ void main(void)
 		/* display temperature */
 		printf("Temperature:%.1f C\n", sensor_value_to_double(&temp));
 
-		/* display humidity (converted from millipercent) */
-		printf("Relative Humidity:%.0f%%\n",
-		       sensor_value_to_double(&hum) / 1000);
+		/* display humidity */
+		printf("Relative Humidity:%.1f%%\n",
+		       sensor_value_to_double(&hum));
 
 		k_sleep(2000);
 	}