drivers: sensor: add support for ALS31300 3D Hall Effect Sensor

Add driver for Allegro Microsystems ALS31300 3-axis linear Hall Effect
sensor. The driver supports:
- I2C communication interface
- X, Y, Z magnetic field measurements
- Device temperature readings

Signed-off-by: Fabian Barraez <[email protected]>

Author: fabocode

drivers/sensor/CMakeLists.txt

@@ -39,6 +39,7 @@ add_subdirectory(wsen)
 # zephyr-keep-sorted-stop
 
 add_subdirectory_ifdef(CONFIG_A01NYUB a01nyub)
+add_subdirectory_ifdef(CONFIG_ALS31300 als31300)
 add_subdirectory_ifdef(CONFIG_AMD_SB_TSI amd_sb_tsi)
 add_subdirectory_ifdef(CONFIG_AMG88XX amg88xx)
 add_subdirectory_ifdef(CONFIG_APDS9253 apds9253)

drivers/sensor/Kconfig

@@ -88,6 +88,7 @@ comment "Device Drivers"
 
 # zephyr-keep-sorted-start
 source "drivers/sensor/adi/Kconfig"
+source "drivers/sensor/als31300/Kconfig"
 source "drivers/sensor/ams/Kconfig"
 source "drivers/sensor/aosong/Kconfig"
 source "drivers/sensor/asahi_kasei/Kconfig"

drivers/sensor/als31300/CMakeLists.txt

@@ -0,0 +1,7 @@
+# Copyright (c) 2025 Croxel
+# SPDX-License-Identifier: Apache-2.0
+
+zephyr_library()
+
+zephyr_library_sources(als31300.c)
+zephyr_library_sources_ifdef(CONFIG_SENSOR_ASYNC_API als31300_async.c als31300_decoder.c)

drivers/sensor/als31300/Kconfig

@@ -0,0 +1,14 @@
+# Copyright (c) 2025 Croxel
+# SPDX-License-Identifier: Apache-2.0
+
+# ALS31300 3D Linear Hall-Effect Sensor configuration options
+
+config ALS31300
+	bool "ALS31300 3D Linear Hall-Effect Sensor"
+	default y
+	depends on DT_HAS_ALLEGRO_ALS31300_ENABLED
+	select I2C
+	help
+	  Enable driver for ALS31300 3D Linear Hall-Effect Sensor.
+	  This sensor provides 12-bit magnetic field measurements
+	  on X, Y, and Z axes via I2C interface.

drivers/sensor/als31300/als31300.c

@@ -0,0 +1,279 @@
+/*
+ * Copyright (c) 2025 Croxel
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+#define DT_DRV_COMPAT allegro_als31300
+
+#include "als31300.h"
+
+#include <zephyr/device.h>
+#include <zephyr/drivers/sensor.h>
+#include <zephyr/logging/log.h>
+#include <zephyr/kernel.h>
+#include <zephyr/sys/util.h>
+#include <zephyr/drivers/i2c.h>
+
+LOG_MODULE_REGISTER(als31300, CONFIG_SENSOR_LOG_LEVEL);
+
+/**
+ * @brief Convert 12-bit two's complement value to signed 16-bit
+ * @param value 12-bit value to convert (bits 11:0)
+ * @return Signed 16-bit value
+ */
+int16_t als31300_convert_12bit_to_signed(uint16_t value)
+{
+	return (int16_t)sign_extend(value, ALS31300_12BIT_SIGN_BIT_INDEX);
+}
+
+/**
+ * @brief Parse raw register data from 8-byte buffer
+ * @param buf 8-byte buffer containing register 0x28 and 0x29 data
+ * @param readings Pointer to readings structure to store parsed data
+ */
+void als31300_parse_registers(const uint8_t *buf, struct als31300_readings *readings)
+{
+	uint32_t reg28_data, reg29_data;
+	uint16_t x_msb, y_msb, z_msb;
+	uint8_t x_lsb, y_lsb, z_lsb;
+	uint8_t temp_msb, temp_lsb;
+
+	/* Convert 8 bytes to two 32-bit values (MSB first) */
+	reg28_data = ((uint32_t)buf[0] << 24) | ((uint32_t)buf[1] << 16) | ((uint32_t)buf[2] << 8) |
+		     ((uint32_t)buf[3]);
+	reg29_data = ((uint32_t)buf[4] << 24) | ((uint32_t)buf[5] << 16) | ((uint32_t)buf[6] << 8) |
+		     ((uint32_t)buf[7]);
+
+	/* Extract fields from register 0x28 */
+	temp_msb = (reg28_data & ALS31300_REG28_TEMP_MSB_MASK) >> ALS31300_REG28_TEMP_MSB_SHIFT;
+	z_msb = (reg28_data & ALS31300_REG28_Z_AXIS_MSB_MASK) >> ALS31300_REG28_Z_AXIS_MSB_SHIFT;
+	y_msb = (reg28_data & ALS31300_REG28_Y_AXIS_MSB_MASK) >> ALS31300_REG28_Y_AXIS_MSB_SHIFT;
+	x_msb = (reg28_data & ALS31300_REG28_X_AXIS_MSB_MASK) >> ALS31300_REG28_X_AXIS_MSB_SHIFT;
+
+	/* Extract fields from register 0x29 */
+	temp_lsb = (reg29_data & ALS31300_REG29_TEMP_LSB_MASK) >> ALS31300_REG29_TEMP_LSB_SHIFT;
+	z_lsb = (reg29_data & ALS31300_REG29_Z_AXIS_LSB_MASK) >> ALS31300_REG29_Z_AXIS_LSB_SHIFT;
+	y_lsb = (reg29_data & ALS31300_REG29_Y_AXIS_LSB_MASK) >> ALS31300_REG29_Y_AXIS_LSB_SHIFT;
+	x_lsb = (reg29_data & ALS31300_REG29_X_AXIS_LSB_MASK) >> ALS31300_REG29_X_AXIS_LSB_SHIFT;
+
+	/* Combine MSB and LSB to form 12-bit values */
+	const uint16_t x_raw = (x_msb << 4) | x_lsb;
+	const uint16_t y_raw = (y_msb << 4) | y_lsb;
+	const uint16_t z_raw = (z_msb << 4) | z_lsb;
+	const uint16_t temp_raw = (temp_msb << 6) | temp_lsb;
+
+	/* Convert to signed values (proper 12-bit two's complement) */
+	readings->x = als31300_convert_12bit_to_signed(x_raw);
+	readings->y = als31300_convert_12bit_to_signed(y_raw);
+	readings->z = als31300_convert_12bit_to_signed(z_raw);
+	readings->temp = temp_raw;
+}
+
+/**
+ * @brief Convert raw magnetic field value to microgauss
+ * This function converts the 12-bit signed raw magnetic field value to
+ * microgauss units
+ * Formula: microgauss = (raw_value * 500 * 1000000) / 4096
+ * @param raw_value Signed 12-bit magnetic field value
+ * @return Magnetic field in microgauss
+ */
+int32_t als31300_convert_to_gauss(int16_t raw_value)
+{
+	/* Convert to microgauss
+	 * For 500G full scale: (raw_value * 500 * 1000000) / 4096
+	 * This gives us the fractional part in microgauss
+	 */
+	return ((int64_t)raw_value * ALS31300_FULL_SCALE_RANGE_GAUSS * 1000000) /
+	       ALS31300_12BIT_RESOLUTION;
+}
+
+/**
+ * @brief Convert raw temperature value to celsius
+ * Based on datasheet formula: T(°C) = 302 * (raw_temp - 1708) / 4096
+ * @param raw_temp 12-bit raw temperature value
+ * @return Temperature in microcelsius
+ */
+int32_t als31300_convert_temperature(uint16_t raw_temp)
+{
+	/* Convert to microcelsius
+	 * Formula: microcelsius = (302 * (raw_temp - 1708) * 1000000) / 4096
+	 */
+	return ((int64_t)ALS31300_TEMP_SCALE_FACTOR * ((int32_t)raw_temp - ALS31300_TEMP_OFFSET) *
+		1000000) /
+	       ALS31300_TEMP_DIVISOR;
+}
+
+/**
+ * @brief Read and parse sensor data from ALS31300
+ * This function performs an 8-byte I2C burst read from registers 0x28 and 0x29
+ * to get magnetic field and temperature data. The data is parsed according to
+ * the datasheet bit field layout and stored in the provided readings structure.
+ * @param dev Pointer to the device structure
+ * @param readings Pointer to readings structure to store data
+ * @return 0 on success, negative error code on failure
+ */
+static int als31300_read_sensor_data(const struct device *dev, enum sensor_channel chan,
+				     struct als31300_readings *readings)
+{
+	const struct als31300_config *cfg = dev->config;
+	struct als31300_data *data = dev->data;
+	uint8_t buf[8];
+	int ret;
+
+	/* Read both data registers in a single 8-byte transaction for consistency */
+	ret = i2c_burst_read_dt(&cfg->i2c, ALS31300_REG_DATA_28, buf, sizeof(buf));
+	if (ret < 0) {
+		LOG_ERR("Failed to read sensor data: %d", ret);
+		return ret;
+	}
+
+	/* Parse the register data using common helper */
+	als31300_parse_registers(buf, readings);
+
+	/* Also update local data structure for compatibility */
+	data->x_raw = readings->x;
+	data->y_raw = readings->y;
+	data->z_raw = readings->z;
+	data->temp_raw = readings->temp;
+
+	return 0;
+}
+
+static int als31300_sample_fetch(const struct device *dev, enum sensor_channel chan)
+{
+	struct als31300_readings readings;
+
+	return als31300_read_sensor_data(dev, chan, &readings);
+}
+
+static int als31300_channel_get(const struct device *dev, enum sensor_channel chan,
+				struct sensor_value *val)
+{
+	struct als31300_data *data = dev->data;
+	int32_t raw_val;
+	int32_t converted_val;
+
+	switch (chan) {
+	case SENSOR_CHAN_MAGN_X:
+		raw_val = data->x_raw;
+		break;
+	case SENSOR_CHAN_MAGN_Y:
+		raw_val = data->y_raw;
+		break;
+	case SENSOR_CHAN_MAGN_Z:
+		raw_val = data->z_raw;
+		break;
+	case SENSOR_CHAN_AMBIENT_TEMP:
+		/* Temperature conversion */
+		converted_val = als31300_convert_temperature(data->temp_raw);
+		sensor_value_from_micro(val, converted_val);
+		return 0;
+	default:
+		return -ENOTSUP;
+	}
+
+	/* Convert raw magnetic data to gauss */
+	converted_val = als31300_convert_to_gauss(raw_val);
+	sensor_value_from_micro(val, converted_val);
+
+	return 0;
+}
+
+static DEVICE_API(sensor, als31300_api) = {
+	.sample_fetch = als31300_sample_fetch,
+	.channel_get = als31300_channel_get,
+#ifdef CONFIG_SENSOR_ASYNC_API
+	.submit = als31300_submit,
+	.get_decoder = als31300_get_decoder,
+#endif
+};
+
+/**
+ * @brief Configure ALS31300 to Active Mode
+ * This function sets the device to Active Mode by writing to the volatile
+ * register 0x27. This register can be written without customer access mode.
+ * @param dev Pointer to the device structure
+ * @return 0 on success, negative error code on failure
+ */
+static int als31300_configure_device(const struct device *dev)
+{
+	const struct als31300_config *cfg = dev->config;
+	uint32_t reg27_value = 0x00000000; /* All bits to 0 = Active Mode */
+	int ret;
+
+	LOG_INF("Configuring ALS31300 to Active Mode...");
+
+	/* Write 0x00000000 to register 0x27 to set Active Mode
+	 * Bits [1:0] = 0 → Active Mode
+	 * Bits [3:2] = 0 → Single read mode (default I2C mode)
+	 * Bits [6:4] = 0 → Low-power count = 0.5ms (doesn't matter in Active Mode)
+	 * Bits [31:7] = 0 → Reserved (should be 0)
+	 */
+	ret = i2c_burst_write_dt(&cfg->i2c, ALS31300_REG_VOLATILE_27, (uint8_t *)&reg27_value,
+				 sizeof(reg27_value));
+	if (ret < 0) {
+		LOG_ERR("Failed to write to register 0x27: %d", ret);
+		return ret;
+	}
+
+	return 0;
+}
+
+/**
+ * @brief Initialize ALS31300 device
+ */
+static int als31300_init(const struct device *dev)
+{
+	const struct als31300_config *cfg = dev->config;
+	int ret;
+
+	if (!i2c_is_ready_dt(&cfg->i2c)) {
+		LOG_ERR("I2C device not ready");
+		return -ENODEV;
+	}
+
+	/* Wait for power-on delay as specified in datasheet */
+	k_usleep(ALS31300_POWER_ON_DELAY_US);
+
+	/* Test communication by reading a register (can be done without customer access) */
+	uint8_t test_val;
+
+	ret = i2c_reg_read_byte_dt(&cfg->i2c, ALS31300_REG_VOLATILE_27, &test_val);
+	if (ret < 0) {
+		LOG_ERR("Failed to communicate with sensor: %d", ret);
+		return ret;
+	}
+
+	/* Configure device to Active Mode */
+	ret = als31300_configure_device(dev);
+	if (ret < 0) {
+		LOG_ERR("Failed to configure device: %d", ret);
+		return ret;
+	}
+
+	/* Wait a bit more for the sensor to be fully ready in Active Mode */
+	k_msleep(ALS31300_REG_WRITE_DELAY_MS);
+
+	return 0;
+}
+
+#define ALS31300_INIT(inst)                                                                        \
+	RTIO_DEFINE(als31300_rtio_ctx_##inst, 16, 16);                                             \
+	I2C_DT_IODEV_DEFINE(als31300_bus_##inst, DT_DRV_INST(inst));                               \
+                                                                                                   \
+	static struct als31300_data als31300_data_##inst;                                          \
+                                                                                                   \
+	static const struct als31300_config als31300_config_##inst = {                             \
+		.i2c = I2C_DT_SPEC_INST_GET(inst),                                                 \
+		.bus =                                                                             \
+			{                                                                          \
+				.ctx = &als31300_rtio_ctx_##inst,                                  \
+				.iodev = &als31300_bus_##inst,                                     \
+			},                                                                         \
+	};                                                                                         \
+                                                                                                   \
+	SENSOR_DEVICE_DT_INST_DEFINE(inst, als31300_init, NULL, &als31300_data_##inst,             \
+				     &als31300_config_##inst, POST_KERNEL,                         \
+				     CONFIG_SENSOR_INIT_PRIORITY, &als31300_api)
+
+DT_INST_FOREACH_STATUS_OKAY(ALS31300_INIT);