Add bh1750 (I2C light sensor) driver

extras/bh1750/bh1750.c

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+/*
+ * Driver for BH1750 light sensor
+ *
+ * Part of esp-open-rtos
+ * Copyright (C) 2017 Andrej Krutak <dev@andree.sk>
+ * BSD Licensed as described in the file LICENSE
+ */
+#include "bh1750.h"
+#include <i2c/i2c.h>
+#include <stdio.h>
+
+void bh1750_configure(uint8_t addr, uint8_t mode)
+{
+	i2c_slave_write(addr, NULL, &mode, 1);
+}
+
+uint16_t bh1750_read(uint8_t addr)
+{
+	uint8_t buf[2];
+	uint16_t level;
+
+	i2c_slave_read(addr, NULL, buf, 2);
+
+	level = buf[0] << 8 | buf[1];
+	level = (level * 10) / 12; // convert to LUX
+
+	return level;
+}

extras/bh1750/bh1750.h

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+/*
+ * Driver for BH1750 light sensor
+ *
+ * Part of esp-open-rtos
+ * Copyright (C) 2017 Andrej Krutak <dev@andree.sk>
+ * BSD Licensed as described in the file LICENSE
+ *
+ * ROHM Semiconductor bh1750fvi-e.pdf
+ */
+#ifndef EXTRAS_BH1750_H_
+#define EXTRAS_BH1750_H_
+
+#include <stdint.h>
+#include <stdbool.h>
+#include <time.h>
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+/* Possible chip addresses */
+#define BH1750_ADDR_LO 0x23 // ADDR pin floating/low
+#define BH1750_ADDR_HI 0x5c
+
+
+/* Configuration options */
+
+// No active state
+#define BH1750_POWER_DOWN 0x00
+
+// Wating for measurement command
+#define BH1750_POWER_ON 0x01
+
+// Reset data register value - not accepted in POWER_DOWN mode
+#define BH1750_RESET 0x07
+
+
+/* Measurement modes */
+
+#define BH1750_CONTINUOUS_MODE  0x10
+#define BH1750_ONE_TIME_MODE  0x20
+
+// Start measurement at 1 lx resolution (measurement time typically 120ms)
+#define BH1750_HIGH_RES_MODE 0x00
+// Start measurement at 0.5 lx resolution  (measurement time typically 120ms)
+#define BH1750_HIGH_RES_MODE2 0x01
+// Start measurement at 4 lx resolution  (measurement time typically 16ms)
+#define BH1750_LOW_RES_MODE 0x03
+
+/* Adjust measurement time to account for optical window size (see datasheet).
+ * Procedure from datasheet suggests order Hi, Low and finally measurement mode
+ */
+#define BH1750_MEASURE_TIME_HI(mt) (0x40 | (((mt) >> 5) & 0x7))
+#define BH1750_MEASURE_TIME_LO(mt) (0x60 | ((mt) & 0x1f))
+#define BH1750_DEFAULT_MEASURE_TIME 0x45
+
+
+/**
+ * Configure the device.
+ * @param addr Device address
+ * @param mode Combination of BH1750_* flags
+ *
+ * May be called multiple times e.g. to configure the measurement time and
+ * the readout mode afterwards - or if one time mode is used consecutively.
+ *
+ * Example: BH1750_ADDR_LO, BH1750_CONTINUOUS_MODE | BH1750_HIGH_RES_MODE
+ */
+void bh1750_configure(uint8_t addr, uint8_t mode);
+
+/**
+ * Read LUX value from the device.
+ *
+ * @param addr Device address
+ * @returns read value in lux units
+ */
+uint16_t bh1750_read(uint8_t addr);
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif /* EXTRAS_BH1750_H_ */

extras/bh1750/component.mk

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+# Component makefile for extras/bh1750
+
+# expected anyone using RTC driver includes it as 'bh1750/bh1750.h'
+INC_DIRS += $(bh1750_ROOT)..
+
+# args for passing into compile rule generation
+bh1750_SRC_DIR =  $(bh1750_ROOT)
+
+$(eval $(call component_compile_rules,bh1750))