drivers/sensors: add LSM6DS3TR-C uORB driver for the XIAO ESP32-S3

No driver exists for this exact chip. lsm6dsl.c is the closest
register-compatible match but is the deprecated legacy char-device
style; lsm6dso32_uorb.c is the closest uORB-style match but is for a
different chip variant. The new driver borrows lsm6dso32_uorb.c's
structure (dual sensor_lowerhalf_s, raw I2C_TRANSFER helpers) and
lsm6dsl.h's register map -- fixing a bug in the header it was ported
from along the way: LSM6DSL_FIFO_CTRL2_SHIFT is defined as 255 instead
of 0.

Delivery mode is chosen the same way mpu6050 does: kthread polling by
default, or interrupt-driven if the board supplies attach(). Unlike
the earlier lsm6dso32-style design this went through first -- one INT
pin and one activate()/interrupt path per sub-sensor -- the shipped
version uses a single shared INT pin for both, mirroring mpu6050's own
one-handler-one-worker design (#19601) instead. The two-independent-
paths version worked for accel alone but was intermittently broken for
gyro: activate() sometimes never actually turned CTRL2_G on even
though the interrupt-enable bit was written correctly, and other times
the whole console hung -- a real race, never conclusively root-caused
on a serial console with no JTAG available. The LSM6DS3TR-C supports
OR'ing both DRDY_XL and DRDY_G onto one pin via independent enable
bits in that pin's INTn_CTRL register, so there was no need for two
paths in the first place: one ISR times the burst, one HPWORK worker
reads OUT_TEMP_L..OUTZ_H_A (14 contiguous bytes covering temp, gyro
and accel in one I2C transaction) and pushes whichever topic(s) are
currently subscribed. activate() now just flips each sub-sensor's own
bit in the shared register instead of running its own attach.

On the XIAO ESP32-S3 with Seeed's IMU Breakout Board, INT1/INT2 route
to GPIO3/GPIO4 (confirmed from the breakout board's schematic, not
guessed). Only INT1/GPIO3 is wired up, since one pin is now enough;
GPIO4/INT2 is documented as available but unused.

Also: CTRL1_XL's FS_XL bits were never actually written to match the
driver's own software default (4g) -- registration set the in-memory
value but the chip stayed at its 2g reset default until a caller
issued an explicit SNIOC_SETFULLSCALE. register() now writes it.

Validated on the bench, both modes, reproduced across multiple fresh
reboots: WHO_AM_I reads 0x6a, sensor_accel0/sensor_gyro0 stream
continuously. Interrupt mode delivers ~300 samples of each per 6s
window with shared timestamps down to the microsecond between the two
topics per event, confirming both come from the same burst read.

Assisted-by: Claude <noreply@anthropic.com>
Signed-off-by: Felipe Moura <moura.fmo@gmail.com>

boards/xtensa/esp32s3/common/src/Make.defs

@@ -66,6 +66,10 @@ ifeq ($(CONFIG_SENSORS_BMP180),y)
   CSRCS += esp32s3_board_bmp180.c
 endif
 
+ifeq ($(CONFIG_SENSORS_LSM6DS3TRC),y)
+  CSRCS += esp32s3_board_lsm6ds3trc.c
+endif
+
 ifeq ($(CONFIG_ESP32S3_OTG),y)
   CSRCS += esp32s3_board_usb.c
 endif

boards/xtensa/esp32s3/common/src/esp32s3_board_lsm6ds3trc.c

@@ -0,0 +1,131 @@
+/****************************************************************************
+ * boards/xtensa/esp32s3/common/src/esp32s3_board_lsm6ds3trc.c
+ *
+ * SPDX-License-Identifier: Apache-2.0
+ *
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.  The
+ * ASF licenses this file to you 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.
+ *
+ ****************************************************************************/
+
+/****************************************************************************
+ * Included Files
+ ****************************************************************************/
+
+#include <nuttx/config.h>
+
+#include <errno.h>
+
+#include <nuttx/i2c/i2c_master.h>
+#include <nuttx/irq.h>
+#include <nuttx/sensors/lsm6ds3trc.h>
+
+#include "espressif/esp_gpio.h"
+#include "esp32s3_i2c.h"
+
+/****************************************************************************
+ * Pre-processor Definitions
+ ****************************************************************************/
+
+/* INT1/INT2 routing on Seeed's "IMU Breakout Board for XIAO" (XIAOML Kit),
+ * confirmed from the board's schematic (IMU_Breakout_Board_for_XIAO_SCH,
+ * rev V1.0): LSM6DS3TR-C INT1 -> XIAO GPIO3 (D2), INT2 -> XIAO GPIO4 (D3),
+ * each through a 33ohm series resistor, both populated. The chip can OR
+ * both DRDY_XL and DRDY_G onto either pin, so only one is used -- INT1 is
+ * an arbitrary but fixed choice. GPIO4/INT2 stays unused by the driver.
+ */
+
+#define LSM6DS3TRC_IRQ_PIN 3  /* INT1 */
+
+/****************************************************************************
+ * Private Functions
+ ****************************************************************************/
+
+/****************************************************************************
+ * Name: board_lsm6ds3trc_attach
+ *
+ * Description:
+ *   Attach (or detach, if handler is NULL) the shared data-ready
+ *   interrupt handler to INT1 (XIAO GPIO3).
+ *
+ ****************************************************************************/
+
+static int board_lsm6ds3trc_attach(xcpt_t handler, FAR void *arg)
+{
+  int ret;
+
+  esp_gpioirqdisable(LSM6DS3TRC_IRQ_PIN);
+
+  ret = esp_gpio_irq(LSM6DS3TRC_IRQ_PIN, handler, arg);
+  if (ret < 0)
+    {
+      return ret;
+    }
+
+  esp_gpioirqenable(LSM6DS3TRC_IRQ_PIN);
+  return OK;
+}
+
+/****************************************************************************
+ * Public Functions
+ ****************************************************************************/
+
+/****************************************************************************
+ * Name: board_lsm6ds3trc_initialize
+ *
+ * Description:
+ *   Initialize and register the LSM6DS3TR-C 6-axis IMU driver, exposing
+ *   it through uORB as /dev/uorb/sensor_accelN and /dev/uorb/sensor_gyroN.
+ *   Data is delivered from the shared INT1 data-ready interrupt rather
+ *   than kthread polling.
+ *
+ * Input Parameters:
+ *   devno - The device number, used to build the uORB device paths
+ *   busno - The I2C bus number
+ *
+ * Returned Value:
+ *   Zero (OK) on success; a negated errno value on failure.
+ *
+ ****************************************************************************/
+
+int board_lsm6ds3trc_initialize(int devno, int busno)
+{
+  struct i2c_master_s *i2c;
+
+  static const struct lsm6ds3trc_config_s config =
+  {
+    .int_pin = LSM6DS3TRC_INT1,
+    .attach = board_lsm6ds3trc_attach,
+  };
+
+  /* The IMU drives INT1 push-pull, active high by default (CTRL3_C
+   * H_LACTIVE reset value) -- rising edge signals data ready. No pull
+   * needed once the sensor drives the line, but PULLDOWN gives a defined
+   * idle state before CTRL registers are written during registration.
+   */
+
+  esp_configgpio(LSM6DS3TRC_IRQ_PIN, INPUT_FUNCTION_2 | PULLDOWN | RISING);
+
+  i2c = esp32s3_i2cbus_initialize(busno);
+  if (i2c == NULL)
+    {
+      return -ENODEV;
+    }
+
+  /* SA0 tied low on this board -> 0x6a. Use 0x6b if SA0 is pulled high. */
+
+  return lsm6ds3trc_register(i2c, 0x6a, devno,
+                             (FAR struct lsm6ds3trc_config_s *)&config);
+}

boards/xtensa/esp32s3/esp32s3-xiao/src/esp32s3-xiao.h

@@ -70,5 +70,33 @@ int esp32s3_bringup(void);
 int esp32s3_gpio_init(void);
 #endif
 
+/****************************************************************************
+ * Name: board_i2c_init
+ ****************************************************************************/
+
+#ifdef CONFIG_I2C_DRIVER
+int board_i2c_init(void);
+#endif
+
+/****************************************************************************
+ * Name: board_lsm6ds3trc_initialize
+ *
+ * Description:
+ *   Initialize and register the LSM6DS3TR-C 6-axis IMU driver, exposing
+ *   it through uORB as /dev/uorb/sensor_accelN and /dev/uorb/sensor_gyroN.
+ *
+ * Input Parameters:
+ *   devno - The device number, used to build the uORB device paths
+ *   busno - The I2C bus number
+ *
+ * Returned Value:
+ *   Zero (OK) on success; a negated errno value on failure.
+ *
+ ****************************************************************************/
+
+#ifdef CONFIG_SENSORS_LSM6DS3TRC
+int board_lsm6ds3trc_initialize(int devno, int busno);
+#endif
+
 #endif /* __ASSEMBLY__ */
 #endif /* __BOARDS_XTENSA_ESP32S3_ESP32S3_XIAO_SRC_ESP32S3_XIAO_H */

boards/xtensa/esp32s3/esp32s3-xiao/src/esp32s3_bringup.c

@@ -47,6 +47,10 @@
 #  include "espressif/esp_hr_timer.h"
 #endif
 
+#ifdef CONFIG_ESP32S3_I2C
+#  include "esp32s3_i2c.h"
+#endif
+
 #include "esp32s3-xiao.h"
 
 #ifdef CONFIG_USERLED
@@ -119,6 +123,28 @@ int esp32s3_bringup(void)
     }
 #endif
 
+#ifdef CONFIG_I2C_DRIVER
+  /* Configure I2C peripheral interfaces */
+
+  ret = board_i2c_init();
+  if (ret < 0)
+    {
+      syslog(LOG_ERR, "Failed to initialize I2C driver: %d\n", ret);
+    }
+#endif
+
+#ifdef CONFIG_SENSORS_LSM6DS3TRC
+  /* Try to register the LSM6DS3TR-C device on I2C0 (D4/D5 = SDA/SCL) */
+
+  ret = board_lsm6ds3trc_initialize(0, ESP32S3_I2C0);
+  if (ret < 0)
+    {
+      syslog(LOG_ERR,
+             "Failed to initialize LSM6DS3TR-C driver for I2C0: %d\n",
+             ret);
+    }
+#endif
+
   /* If we got here then perhaps not all initialization was successful, but
    * at least enough succeeded to bring-up NSH with perhaps reduced
    * capabilities.

drivers/sensors/CMakeLists.txt

@@ -151,6 +151,10 @@ if(CONFIG_SENSORS)
       list(APPEND SRCS lsm6dso32_uorb.c)
     endif()
 
+    if(CONFIG_SENSORS_LSM6DS3TRC)
+      list(APPEND SRCS lsm6ds3trc_uorb.c)
+    endif()
+
     if(CONFIG_SENSORS_LSM9DS1)
       list(APPEND SRCS lsm9ds1_base.c)
       if(CONFIG_SENSORS_LSM9DS1_UORB)

drivers/sensors/Kconfig

@@ -1074,6 +1074,49 @@ config SENSORS_LSM6DSO32_GYRO_ORB_BUFSIZE
 
 endif # SENSORS_LSM6DSO32
 
+config SENSORS_LSM6DS3TRC
+	bool "STM LSM6DS3TR-C support"
+	default n
+	select I2C
+	select SCHED_HPWORK
+	---help---
+		Enable uORB driver support for the STM LSM6DS3TR-C 6-axis IMU
+		over I2C. Needs the high-priority work queue even in kthread
+		polling mode: the driver's interrupt handlers reference it
+		unconditionally (they're only dead code until a future phase wires
+		up INT1/INT2).
+
+if SENSORS_LSM6DS3TRC
+
+config SENSORS_LSM6DS3TRC_I2C_FREQUENCY
+	int "LSM6DS3TR-C I2C frequency"
+	default 400000
+	range 1 400000
+	---help---
+		The I2C frequency used to communicate with the LSM6DS3TR-C.
+
+config SENSORS_LSM6DS3TRC_THREAD_STACKSIZE
+	int "LSM6DS3TR-C worker thread stack size"
+	default 1024
+	---help---
+		The stack size for the worker threads that perform measurements.
+
+config SENSORS_LSM6DS3TRC_ACCEL_ORB_BUFSIZE
+	int "LSM6DS3TR-C accelerometer uORB buffer size"
+	default 10
+	range 0 500
+	---help---
+		The circular buffer size for the accelerometer uORB measurements
+
+config SENSORS_LSM6DS3TRC_GYRO_ORB_BUFSIZE
+	int "LSM6DS3TR-C gyroscope uORB buffer size"
+	default 10
+	range 0 500
+	---help---
+		The circular buffer size for the gyroscope uORB measurements
+
+endif # SENSORS_LSM6DS3TRC
+
 config SENSORS_LSM9DS1
 	bool "STMicro LSM9DS1 support"
 	default n

drivers/sensors/Make.defs

@@ -163,6 +163,10 @@ ifeq ($(CONFIG_SENSORS_LSM6DSO32),y)
   CSRCS += lsm6dso32_uorb.c
 endif
 
+ifeq ($(CONFIG_SENSORS_LSM6DS3TRC),y)
+  CSRCS += lsm6ds3trc_uorb.c
+endif
+
 ifeq ($(CONFIG_SENSORS_LSM9DS1),y)
   CSRCS += lsm9ds1_base.c
   ifeq ($(CONFIG_SENSORS_LSM9DS1_UORB),y)

include/nuttx/sensors/lsm6ds3trc.h

@@ -0,0 +1,99 @@
+/****************************************************************************
+ * include/nuttx/sensors/lsm6ds3trc.h
+ *
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements. See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.  The
+ * ASF licenses this file to you 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.
+ *
+ ****************************************************************************/
+
+#ifndef __INCLUDE_NUTTX_SENSORS_LSM6DS3TRC_H
+#define __INCLUDE_NUTTX_SENSORS_LSM6DS3TRC_H
+
+/****************************************************************************
+ * Included Files
+ ****************************************************************************/
+
+#include <nuttx/irq.h>
+#include <nuttx/i2c/i2c_master.h>
+#include <nuttx/sensors/ioctl.h>
+
+/****************************************************************************
+ * Public Types
+ ****************************************************************************/
+
+/* LSM6DS3TR-C interrupt pins */
+
+enum lsm6ds3trc_int_e
+{
+  LSM6DS3TRC_INT1 = 0, /* Interrupt pin 1 */
+  LSM6DS3TRC_INT2 = 1, /* Interrupt pin 2 */
+};
+
+typedef int (*lsm6ds3trc_attach)(xcpt_t handler, FAR void *arg);
+
+/* Configuration for the LSM6DS3TR-C driver.
+ *
+ * The chip can OR both the accelerometer and gyroscope data-ready flags
+ * onto a single INT pin (each has its own enable bit in that pin's
+ * INT<n>_CTRL register), so one interrupt line is enough for both
+ * sub-sensors -- there's no need for the two independent INT1/INT2 paths
+ * a chip with a single combined DRDY bit would require two pins for.
+ * Mirrors mpu6050_config_s: one shared handler, one shared HPWORK worker
+ * that bursts accel+gyro+temp from one contiguous I2C read and pushes
+ * whichever topic(s) are currently subscribed.
+ *
+ * Leave `attach` NULL to use kthread polling instead (each sub-sensor
+ * polls independently at its own rate, same as always).
+ */
+
+struct lsm6ds3trc_config_s
+{
+  enum lsm6ds3trc_int_e int_pin; /* INT pin both DRDY_XL and DRDY_G use */
+  lsm6ds3trc_attach attach;      /* Attach the interrupt (NULL for kthread) */
+};
+
+/****************************************************************************
+ * Public Function Prototypes
+ ****************************************************************************/
+
+/****************************************************************************
+ * Name: lsm6ds3trc_register
+ *
+ * Description:
+ *   Register the LSM6DS3TR-C as a UORB sensor with accel and gyro topics.
+ *   If used with interrupts and device registration fails, it is the
+ *   caller's responsibility to detach the interrupt handler.
+ *
+ * Input Parameters:
+ *   i2c     - An instance of the I2C interface to use to communicate with
+ *             the LSM6DS3TR-C
+ *   addr    - The I2C address of the LSM6DS3TR-C (0x6a with SA0 low, 0x6b
+ *             with SA0 high).
+ *   devno   - The device number for the UORB topics registered (i.e.
+ *             sensor_accel<n>)
+ *   config  - Configuration setup for interrupt-driven or polling driven
+ *             data fetching. Leave `*_attach` function NULL to use kthread
+ *             polling instead of interrupt handling. Must not be NULL.
+ *
+ * Returned Value:
+ *   Zero (OK) on success; a negated errno value on failure.
+ *
+ ****************************************************************************/
+
+int lsm6ds3trc_register(FAR struct i2c_master_s *i2c, uint8_t addr,
+                        uint8_t devno,
+                        FAR struct lsm6ds3trc_config_s *config);
+
+#endif /* __INCLUDE_NUTTX_SENSORS_LSM6DS3TRC_H */