sensors/nau7802: Add support for the NAU7802

This patch adds support for the NAU7802 24 bit ADC from Nuvoton.
Please read the documentation for more details.

Signed-off-by: Daniel Byshkin <online@bskdany.com>

Documentation/components/drivers/special/sensors.rst

@@ -29,6 +29,7 @@ general interafce.
     sensors/lsm330.rst
     sensors/mcp9600.rst
     sensors/mpl115a.rst
+    sensors/nau7802.rst
     sensors/sht4x.rst
     sensors/lsm6dso32.rst
     sensors/lis2mdl.rst

Documentation/components/drivers/special/sensors/nau7802.rst

@@ -0,0 +1,211 @@
+=======
+NAU7802
+=======
+
+Contributed by Daniel Byshkin.
+
+The Adafruit NAU7802 is a high-resolution 24-bit ADC with an integrated load cell amplifier. It is designed for use with load cells and other sensors that require high precision and low noise measurements. The NAU7802 features a built-in programmable gain amplifier (PGA) that allows for easy calibration and adjustment of the sensor's output.
+
+The driver uses the :doc:`uorb
+</components/drivers/special/sensors/sensors_uorb>` interface.
+
+Application Programming Interface
+=================================
+
+.. code-block:: c
+
+   #include <nuttx/sensors/nau7802.h>
+
+The NAU7802 registration function allows the driver to be registered as a UORB
+driver. Registering this driver will cause the ``/dev/uorb/sensor_force<n>`` topic
+to appear, where ``n`` is the value of ``devno``.
+
+Registering the device in polling mode will create a kernel thread to poll the sensor
+
+.. code-block:: c
+
+   int err = nau7802_register(i2c_master, 0, 0x2a);
+   if(err < 0){
+     printf("Failed to register NAU7802: %d\n", err);
+   }
+
+The following are available commands for the NAU7802 driver:
+
+``SNIOC_RESET``
+----------------
+
+Performs a reset of all registers on the NAU7802.
+
+.. code-block:: c
+
+   orb_ioctl(sensor, SNIOC_RESET);
+
+``SNIOC_SET_GAIN``
+------------------------
+
+This command sets the gain of the NAU7802. The possible values are dictated by the
+``nau7802_gain_e`` enum. The default value is 128x.
+
+.. code-block:: c
+
+   orb_ioctl(sensor, SNIOC_SET_GAIN, NAU7802_GAIN_128);
+
+``SNIOC_SET_INTERVAL``
+------------------------
+
+This commands sets the polling interval of the NAU7802. The possible values are dictated by the
+``nau7802_odr_e`` enum. The default value is 10HZ.
+
+.. code-block:: c
+
+   orb_ioctl(sensor, SNIOC_SET_INTERVAL, NAU7802_ODR_10HZ);
+
+``SNIOC_SET_LDO``
+------------------------
+
+This command sets the LDO voltage of the NAU7802. The possible values are dictated by the
+``nau7802_ldo_e`` enum. The default value is 3.0V.
+
+.. code-block:: c
+
+    orb_ioctl(sensor, SNIOC_SET_LDO, NAU7802_LDO_3V0);
+
+``SNIOC_CALIBRATE``
+------------------------
+
+This commands performs one of the calibration procedures of the NAU7802. The possible calibration modes are:
+
+ - NAU7802_CALMOD_INTERNAL: Removes internal PGA gain and offset errors.
+ - NAU7802_CALMOD_OFFSET: Calibrates the zero point of the sensor. 
+ - NAU7802_CALMOD_GAIN: Calibrates the max value of the sensor. 
+
+.. code-block:: c
+
+   orb_ioctl(sensor, SNIOC_CALIBRATE, NAU7802_CALMOD_INTERNAL);
+
+For the gain calibration mode the user must place a known weight on the sensor. Unfortunately the NAU7802 records it as the maximum value, thus if your loadcell supports up to 100kg you shall put a 100kg weight on. 
+
+A workaround would be to do a manual calibration by placing a smaller known weight and polling the sensor to get an average point, then using such point to offset the recorded values. An example is provided below.
+
+.. code-block:: c
+
+  #include "stdio.h"
+  #include <errno.h>
+  #include <fcntl.h>
+  #include <nuttx/sensors/nau7802.h>
+  #include <signal.h>
+  #include <stdbool.h>
+  #include <stdio.h>
+  #include <stdlib.h>
+  #include <sys/ioctl.h>
+  #include <uORB/uORB.h>
+  #include <unistd.h>
+
+  int get_data(const struct orb_metadata *imu_meta, int imu, struct sensor_force *data) {
+    int err = 0;
+    bool update = false;
+    err = orb_check(imu, &update);
+    if (err < 0) {
+        return err;
+    }
+
+    err = orb_copy(imu_meta, imu, data);
+    if (err < 0) {
+        return err;
+    }
+    return err;
+  }
+
+  int main(int argc, char **argv) {
+    int err;
+    int imu;
+    char *name = "sensor_force0";
+
+    const struct orb_metadata *imu_meta = orb_get_meta(name);
+    if (imu_meta == NULL) {
+        fprintf(stderr, "Failed to get metadata for %s\n", name);
+        return EXIT_FAILURE;
+    }
+
+    imu = orb_subscribe(imu_meta);
+    if (imu < 0) {
+        fprintf(stderr, "Could not subsribe to %s: %d\n", name, errno);
+        return EXIT_FAILURE;
+    }
+
+    struct sensor_force data;
+
+    // flush 10 readings
+    for (int i = 0; i < 10; i++) {
+        err = get_data(imu_meta, imu, &data);
+        if (err < 0) {
+            printf("Error reading data\n");
+        }
+        usleep(100000); 
+    }
+
+    long zero_point = 0;
+    for (int i = 0; i < 10; i++) {
+        err = get_data(imu_meta, imu, &data);
+        if (err < 0) {
+            printf("Error reading data\n");
+        } else {
+            zero_point += data.force / 10;
+        }
+        usleep(100000); 
+    }
+    printf("Zero point: %ld\n", zero_point);
+
+    printf("Place weigth on the sensor... you have 5 seconds from when you see this message\n");
+    usleep(5000000);
+    printf("Starting gain calibration\n");
+
+    long weight_point = 0;
+    for (int i = 0; i < 10; i++) {
+        err = get_data(imu_meta, imu, &data);
+        if (err < 0) {
+            printf("Error reading data\n");
+        } else {
+            weight_point += data.force / 10;
+        }
+        usleep(100000);
+    }
+    printf("Weight value: %ld\n", weight_point);
+    float known_weight_val = 15000; // 1.5kg
+
+    while (true) {
+        err = get_data(imu_meta, imu, &data);
+        if (err < 0) {
+            printf("Error reading data\n");
+        } else {
+            printf("Force: %.3f\n", known_weight_val * (data.force - zero_point) / (weight_point - zero_point));
+        }
+        usleep(50000);
+    }
+
+    orb_unsubscribe(imu);
+    return EXIT_SUCCESS;
+  }  
+
+
+
+``SNIOC_GET_CALIBVALUE:``
+----------------------------
+
+This commands gets the gain calibration value when set by the ``SNIOC_CALIBRATE`` command. 
+
+.. code-block:: c
+
+    uint32_t cal_value;
+    orb_ioctl(sensor, SNIOC_GET_CALIBVALUE, (unsigned long)&cal_value);
+
+
+``SNIOC_SET_CALIBVALUE:``
+---------------------------
+
+This commands sets the gain calibration value, useful when you calibrated the sensor with the gain calibration mode once and want to reuse it later on.
+
+.. code-block:: c
+
+    uint32_t cal_value;
+    orb_ioctl(sensor, SNIOC_SET_CALIBVALUE, cal_value);

Documentation/components/drivers/special/sensors/sensors_uorb.rst

@@ -489,6 +489,7 @@ Implemented Drivers
 - ltr308
 - mpu9250
 - ms56xx
+- :doc:`nau7802`
 - :doc:`sht4x`
 - :doc:`lsm6dso32`
 - wtgahrs2

drivers/sensors/Kconfig

@@ -194,6 +194,13 @@ config SENSORS_BH1750FVI
 	---help---
 		Enable driver support for the Rohm BH1750FVI light sensor.
 
+config SENSORS_NAU7802
+	bool "Adafruit NAU7802 ADC sensor support"
+	default n
+	select I2C 
+	---help---
+		Enable driver support for the Adafruit NAU7802 sensor.
+
 config BH1750FVI_I2C_FREQUENCY
 	int "BH1750FVI I2C frequency"
 	default 400000

drivers/sensors/Make.defs

@@ -34,6 +34,11 @@ ifeq ($(CONFIG_SENSORS_RPMSG),y)
   CSRCS += sensor_rpmsg.c
 endif
 
+
+ifeq ($(CONFIG_SENSORS_NAU7802),y)
+  CSRCS += nau7802.c
+endif
+
 ifeq ($(CONFIG_SENSORS_GNSS),y)
   CSRCS += gnss_uorb.c
 endif

include/nuttx/sensors/ioctl.h

@@ -480,6 +480,24 @@
 
 #define SNIOC_LPF                     _SNIOC(0x00A0)
 
+/* Command:      SNIOC_SET_GAIN
+ * Description:  Sets the gain of the sensor.
+ */
+
+#define SNIOC_SET_GAIN                _SNIOC(0x00A1)
+
+/* Command:      SNIOC_SET_LDO
+ * Description:  Sets the LDO voltage of the sensor.
+ */
+
+#define SNIOC_SET_LDO                 _SNIOC(0x00A2)
+
+/* Command:      SNIOC_GET_CALIBVALUE
+ * Description:  Get the gain calibration value of the sensor.
+ */
+
+#define SNIOC_GET_CALIBVALUE          _SNIOC(0x00A3)
+
 /****************************************************************************
  * Public types
  ****************************************************************************/

include/nuttx/sensors/nau7802.h

@@ -0,0 +1,108 @@
+/****************************************************************************
+ * include/nuttx/sensors/nau7802.h
+ *
+ * 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/irq.h>
+#include <nuttx/sensors/ioctl.h>
+
+/****************************************************************************
+ * Public Types
+ ****************************************************************************/
+
+struct i2c_master_s; /* Forward reference */
+
+typedef int (*nau7802_attach)(xcpt_t, FAR void *arg);
+
+/* Valid calibration modes */
+
+typedef enum
+{
+  NAU7802_CALMOD_INTERNAL = 0,
+  NAU7802_CALMOD_OFFSET = 2,
+  NAU7802_CALMOD_GAIN = 3
+} nau7802_calibmode_e;
+
+/* Valid LDO voltage settings */
+
+typedef enum
+{
+  NAU7802_LDO_V_4V5,
+  NAU7802_LDO_V_4V2,
+  NAU7802_LDO_V_3V9,
+  NAU7802_LDO_V_3V6,
+  NAU7802_LDO_V_3V3,
+  NAU7802_LDO_V_3V0,
+  NAU7802_LDO_V_2V7,
+  NAU7802_LDO_V_2V4,
+  NAU7802_LDO_V_EXTERNAL
+} nau7802_ldo_e;
+
+/* Valid gain settings */
+
+typedef enum
+{
+  NAU7802_GAIN_1,
+  NAU7802_GAIN_2,
+  NAU7802_GAIN_4,
+  NAU7802_GAIN_8,
+  NAU7802_GAIN_16,
+  NAU7802_GAIN_32,
+  NAU7802_GAIN_64,
+  NAU7802_GAIN_128
+} nau7802_gain_e;
+
+/* Valid odr values */
+
+typedef enum
+{
+  NAU7802_ODR_10HZ = 0,
+  NAU7802_ODR_20HZ = 1,
+  NAU7802_ODR_40HZ = 2,
+  NAU7802_ODR_80HZ = 3,
+  NAU7802_ODR_320HZ = 7
+} nau7802_odr_e;
+
+/****************************************************************************
+ * Public Function Prototypes
+ ****************************************************************************/
+
+/****************************************************************************
+ * Name: nau7802_register
+ *
+ * Description:
+ *   Register the nau7802 device as a UORB sensor.
+ *
+ * Input Parameters:
+ *   i2c     - An instance of the I2C interface to use to communicate with
+ *             the nau7802.
+ *   addr    - The I2C address of the nau7802. Should always be 0x2a.
+ *   devno   - The device number to use for the topic (i.e. /dev/mag0)
+ *
+ * Returned Value:
+ *   Zero (OK) on success; a negated errno value on failure.
+ *
+ ****************************************************************************/
+
+int nau7802_register(FAR struct i2c_master_s *i2c, int devno, uint8_t addr);