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drivers: sensor: Add support for BH1730 ambient light sensor
This commit adds support for BH1730 ambient light sensor. Signed-off-by: Borislav Kereziev <b.kereziev@gmail.com>
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‎drivers/sensor/rohm/CMakeLists.txt

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# zephyr-keep-sorted-start
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add_subdirectory_ifdef(CONFIG_BD8LB600FS_DIAGNOSTICS bd8lb600fs)
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add_subdirectory_ifdef(CONFIG_BH1730 bh1730)
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add_subdirectory_ifdef(CONFIG_BH1750 bh1750)
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# zephyr-keep-sorted-stop

‎drivers/sensor/rohm/Kconfig

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# zephyr-keep-sorted-start
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source "drivers/sensor/rohm/bd8lb600fs/Kconfig"
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source "drivers/sensor/rohm/bh1730/Kconfig"
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source "drivers/sensor/rohm/bh1750/Kconfig"
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# zephyr-keep-sorted-stop

‎drivers/sensor/rohm/bh1730/CMakeLists.txt

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# SPDX-License-Identifier: Apache-2.0
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zephyr_library()
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zephyr_library_sources(bh1730.c)

‎drivers/sensor/rohm/bh1730/Kconfig

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# BH1730 ambient light sensor configuration options
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# Copyright (c) 2025, Borislav Kereziev
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# SPDX-License-Identifier: Apache-2.0
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config BH1730
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bool "BH1730 Ambient Light Sensor"
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default y
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depends on DT_HAS_ROHM_BH1730_ENABLED
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select I2C
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help
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Enable driver for BH1730 ambient light sensor.

‎drivers/sensor/rohm/bh1730/bh1730.c

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/*
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* Copyright (c) 2025, Borislav Kereziev
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*
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* SPDX-License-Identifier: Apache-2.0
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*/
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#define DT_DRV_COMPAT rohm_bh1730
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#include <errno.h>
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#include <zephyr/drivers/i2c.h>
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#include <zephyr/drivers/sensor.h>
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#include <zephyr/logging/log.h>
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LOG_MODULE_REGISTER(BH1730, CONFIG_SENSOR_LOG_LEVEL);
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#define BH1730_REG_CONTROL 0x00
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#define BH1730_REG_TIMING 0x01
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#define BH1730_REG_GAIN 0x07
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#define BH1730_REG_ID 0x12
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#define BH1730_REG_DATA0LOW 0x14
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#define BH1730_REG_DATA0HIGH 0x15
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#define BH1730_REG_DATA1LOW 0x16
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#define BH1730_REG_DATA1HIGH 0x17
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#define BH1730_PART_ID 0x71
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#define BH1730_GAIN_DEFAULT 0x0
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#define BH1730_ITIME_DEFAULT 0xDA
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#define BH1730_CONTROL_ADC_EN_POWER_ON_SINGLE_READING 0x0B
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#define BH1730_CONTROL_ADC_EN_POWER_ON 0x03
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#define BH1730_CONTROL_ADC_DATA_UPDATED (1 << 4)
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#define BH1730_TINT 2.8E-9 /* Internal clock period Tint */
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#define BH1730_CMD 0x80 /* Command register CMD bit */
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#define BH1730_CMD_ADDR_MASK 0x1F
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/* Data definitions */
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struct bh1730_data {
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uint16_t data0; /* visible light */
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uint16_t data1; /* infrared light */
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};
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struct bh1730_config {
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struct i2c_dt_spec i2c;
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uint8_t gain;
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uint8_t itime;
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};
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/* Prototypes */
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static int bh1730_reg_read_8(const struct device *dev, uint8_t reg, uint8_t *val);
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static int bh1730_reg_write_8(const struct device *dev, uint8_t reg, uint8_t val);
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static int bh1730_data_read(const struct device *dev, uint16_t *data0, uint16_t *data1);
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static uint32_t bh1730_get_integration_time_ms(uint8_t itime_reg);
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static uint8_t bh1730_get_gain(uint8_t gain_reg_val);
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static uint32_t bh1730_calculate_lux(uint16_t data0, uint16_t data1, uint8_t itime_reg,
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uint8_t gain_reg);
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static int bh1730_sample_fetch(const struct device *dev, enum sensor_channel chan);
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static int bh1730_sample_get(const struct device *dev, enum sensor_channel chan,
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struct sensor_value *val);
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static int bh1730_init(const struct device *dev);
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/* Functions */
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static int bh1730_reg_read_8(const struct device *dev, uint8_t reg, uint8_t *val)
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{
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const struct bh1730_config *cfg = dev->config;
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uint8_t cmd = BH1730_CMD | (reg & BH1730_CMD_ADDR_MASK);
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return i2c_write_read_dt(&cfg->i2c, &cmd, sizeof(cmd), val, sizeof(*val));
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}
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static int bh1730_reg_write_8(const struct device *dev, uint8_t reg, uint8_t val)
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{
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const struct bh1730_config *cfg = dev->config;
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uint8_t cmd = BH1730_CMD | (reg & BH1730_CMD_ADDR_MASK);
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uint8_t buf[2] = {cmd, val};
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return i2c_write_dt(&cfg->i2c, buf, sizeof(buf));
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}
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static int bh1730_data_read(const struct device *dev, uint16_t *data0, uint16_t *data1)
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{
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const struct bh1730_config *cfg = dev->config;
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/* Ensure data has been updated */
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uint8_t control_reg = 0x0;
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int err = bh1730_reg_read_8(dev, BH1730_REG_CONTROL, &control_reg);
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if (err) {
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LOG_ERR("Failed reading CONTROL register");
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return -EIO;
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}
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if ((control_reg & BH1730_CONTROL_ADC_DATA_UPDATED) == 0) {
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LOG_ERR("Data not updated");
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return -ENODATA;
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}
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/* Read data0 and data1 bytes */
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uint8_t buffer[4] = {0};
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uint8_t cmd = BH1730_CMD | BH1730_REG_DATA0LOW;
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err = i2c_write_read_dt(&cfg->i2c, &cmd, sizeof(cmd), &buffer, sizeof(buffer));
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if (err) {
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return -EIO;
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}
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/* Data is shifted LSB first from sensor - swap */
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*data0 = (buffer[1] << 8 | buffer[0]);
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*data1 = (buffer[3] << 8 | buffer[2]);
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return 0;
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}
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static inline uint32_t bh1730_get_integration_time_ms(uint8_t itime_reg)
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{
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/* Convert register to integration time in ms */
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const uint32_t K_scaled = 2699200; /* 2.8e-6 * 964 * 1000 * 1e6 */
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uint32_t integration_time_ms;
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integration_time_ms = (K_scaled * (256 - itime_reg)) / 1000000;
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return integration_time_ms;
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}
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static inline uint8_t bh1730_get_gain(uint8_t gain_reg_val)
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{
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/* Convert register value to gain */
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if (gain_reg_val == 0x0) {
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return 1;
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}
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if (gain_reg_val == 0x01) {
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return 2;
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}
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if (gain_reg_val == 0x02) {
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return 64;
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}
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if (gain_reg_val == 0x03) {
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return 128;
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}
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return 1;
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}
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static uint32_t bh1730_calculate_lux(uint16_t data0, uint16_t data1, uint8_t itime_reg,
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uint8_t gain_reg)
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{
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/* Check page 13 of datasheet for lux calculation formula */
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const uint32_t SCALE = 1000;
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const uint32_t scale1026 = 102600; /* 102.6 * 1000 */
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/* prevent division by zero */
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if (data0 == 0) {
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return 0;
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}
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uint32_t itime_ms = bh1730_get_integration_time_ms(itime_reg);
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uint8_t gain = bh1730_get_gain(gain_reg);
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/* Compute ratio = (DATA1 / DATA0) scaled by 1000 */
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uint32_t ratio = ((uint32_t)data1 * SCALE) / data0;
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uint32_t k0_scaled, k1_scaled;
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if (ratio < 260) {
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k0_scaled = 1290;
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k1_scaled = 2733;
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} else if (ratio < 550) {
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k0_scaled = 795;
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k1_scaled = 859;
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} else if (ratio < 1090) {
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k0_scaled = 510;
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k1_scaled = 345;
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} else if (ratio < 2130) {
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k0_scaled = 276;
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k1_scaled = 130;
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} else {
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return 0;
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}
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/* Compute numerator (scaled values, may be negative → use int64_t) */
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int64_t numerator = (int64_t)data0 * k0_scaled - (int64_t)data1 * k1_scaled;
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uint64_t denominator = (uint64_t)gain * scale1026;
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if (numerator <= 0 || denominator == 0) {
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return 0;
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}
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uint32_t lux = (uint32_t)((numerator * itime_ms) / denominator);
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return lux;
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}
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static int bh1730_sample_fetch(const struct device *dev, enum sensor_channel chan)
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{
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struct bh1730_data *data = dev->data;
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const struct bh1730_config *cfg = dev->config;
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if ((chan != SENSOR_CHAN_ALL) && (chan != SENSOR_CHAN_LIGHT)) {
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LOG_ERR("Unsupported channel %d", chan);
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return -ENOTSUP;
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}
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/* Trigger measurement */
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int ret = bh1730_reg_write_8(dev, BH1730_REG_CONTROL,
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BH1730_CONTROL_ADC_EN_POWER_ON_SINGLE_READING);
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if (ret) {
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LOG_ERR("Failed writing to CONTROL register");
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return -EIO;
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}
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/* Wait for conversion */
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int32_t sleep_period_ms = bh1730_get_integration_time_ms(cfg->itime);
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k_msleep(sleep_period_ms);
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/* Read conversion result from device */
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ret = bh1730_data_read(dev, &data->data0, &data->data1);
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if (ret) {
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LOG_ERR("Failed reading data from sensor");
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return -EIO;
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}
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return 0;
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}
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static int bh1730_sample_get(const struct device *dev, enum sensor_channel chan,
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struct sensor_value *val)
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{
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struct bh1730_data *data = dev->data;
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const struct bh1730_config *cfg = dev->config;
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if (chan != SENSOR_CHAN_ALL && chan != SENSOR_CHAN_LIGHT) {
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return -ENOTSUP;
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}
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uint32_t lux = bh1730_calculate_lux(data->data0, data->data1, cfg->itime, cfg->gain);
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val->val1 = lux;
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val->val2 = 0;
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return 0;
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}
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static int bh1730_init(const struct device *dev)
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{
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const struct bh1730_config *cfg = dev->config;
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int ret = 0;
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LOG_DBG("Initializing");
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if (!i2c_is_ready_dt(&cfg->i2c)) {
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LOG_ERR("I2C device not ready");
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return -ENODEV;
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}
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/* Ensure BH1730 has valid ID */
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uint8_t val = 0;
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ret = bh1730_reg_read_8(dev, BH1730_REG_ID, &val);
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if (ret != 0) {
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LOG_ERR("Failed reading ID reg");
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return -ENODEV;
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}
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/* Part number in bits 7:4 */
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if ((val >> 4) != (BH1730_PART_ID >> 4)) {
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LOG_ERR("Part number does not match, received 0x%1X", val >> 4);
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return -ENODEV;
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}
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/* Configure part with gain */
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if (cfg->gain != BH1730_GAIN_DEFAULT) {
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ret = bh1730_reg_write_8(dev, BH1730_REG_GAIN, cfg->gain);
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if (ret) {
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LOG_ERR("Failed writing to gain register");
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return -EIO;
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}
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}
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/* Configure part with itime */
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if (cfg->itime != BH1730_ITIME_DEFAULT) {
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ret = bh1730_reg_write_8(dev, BH1730_REG_TIMING, cfg->itime);
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if (ret) {
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LOG_ERR("Failed writing to ITIME register");
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return -EIO;
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}
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}
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return ret;
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}
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static DEVICE_API(sensor, bh1730_api) = {.sample_fetch = bh1730_sample_fetch,
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.channel_get = bh1730_sample_get};
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#define BH1730_DEFINE(inst) \
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static struct bh1730_data bh1730_data_##inst; \
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static const struct bh1730_config bh1730_config_##inst = { \
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.i2c = I2C_DT_SPEC_INST_GET(inst), \
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.gain = DT_INST_PROP(inst, gain), \
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.itime = DT_INST_PROP(inst, itime), \
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}; \
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SENSOR_DEVICE_DT_INST_DEFINE(inst, bh1730_init, NULL, &bh1730_data_##inst, \
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&bh1730_config_##inst, POST_KERNEL, \
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CONFIG_SENSOR_INIT_PRIORITY, &bh1730_api);
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DT_INST_FOREACH_STATUS_OKAY(BH1730_DEFINE)

‎dts/bindings/sensor/rohm,bh1730.yaml

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# Copyright (c) 2025, Borislav Kereziev
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# SPDX-License-Identifier: Apache-2.0
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description: Rohm BH1730 ambient light sensor.
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compatible: "rohm,bh1730"
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include: [sensor-device.yaml, i2c-device.yaml]
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properties:
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gain:
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type: int
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default: 0
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description: |
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ADC resolution setting
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0 = x1 gain mode
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1 = x2 gain mode
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2 = x64 gain mode
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3 = x128 gain mode
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Lower gain values (x1 and x2) reduce sensitivity and prevent
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saturation in brighter environments.
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Higher gain values (x64 and x128) result in higher sensitivity,
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which are useful in low-light environments.
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The default corresponds to the reset value of the GAIN register.
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enum:
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- 0
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- 1
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- 2
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- 3
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itime:
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type: int
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default: 0xDA
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description: |
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ITIME value in TIMING register determines integration time.
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Higher values result in longer integration time and
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increased accuracy.
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The default corresponds to the reset value of the TIMING register.

‎tests/drivers/build_all/sensor/i2c.dtsi

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@@ -1302,3 +1302,8 @@ test_i2c_rm3100: rm3100@b2 {
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reg = <0xb2>;
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int-gpios = <&test_gpio 0 0>;
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};
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test_i2c_bh1730: bh1730@b3 {
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compatible = "rohm,bh1730";
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reg = <0xb3>;
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};

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