Sensors
The sensor subsystem exposes an API to uniformly access sensor devices. Common operations are: reading data and executing code when specific conditions are met.
Basic Operation
Channels
Fundamentally, a channel is a quantity that a sensor device can measure.
Sensors can have multiple channels, either to represent different axes of the same physical property (e.g. acceleration); or because they can measure different properties altogether (ambient temperature, pressure and humidity). Complex sensors cover both cases, so a single device can expose three acceleration channels and a temperature one.
It is imperative that all sensors that support a given channel express results in the same unit of measurement. Consult the API Reference for all supported channels, along with their description and units of measurement:
Values
Sensor devices return results as sensor_value
. This
representation avoids use of floating point values as they may not be
supported on certain setups.
Fetching Values
Getting a reading from a sensor requires two operations. First, an
application instructs the driver to fetch a sample of all its channels.
Then, individual channels may be read. In the case of channels with
multiple axes, they can be read in a single operation by supplying
the corresponding _XYZ
channel type and a buffer of 3
sensor_value
objects. This approach ensures consistency
of channels between reads and efficiency of communication by issuing a
single transaction on the underlying bus.
Below is an example illustrating the usage of the BME280 sensor, which
measures ambient temperature and atmospheric pressure. Note that
sensor_sample_fetch()
is only called once, as it reads and
compensates data for both channels.
1
2/*
3 * Get a device structure from a devicetree node with compatible
4 * "bosch,bme280". (If there are multiple, just pick one.)
5 */
6static const struct device *get_bme280_device(void)
7{
8 const struct device *dev = DEVICE_DT_GET_ANY(bosch_bme280);
9
10 if (dev == NULL) {
11 /* No such node, or the node does not have status "okay". */
12 printk("\nError: no device found.\n");
13 return NULL;
14 }
15
16 if (!device_is_ready(dev)) {
17 printk("\nError: Device \"%s\" is not ready; "
18 "check the driver initialization logs for errors.\n",
19 dev->name);
20 return NULL;
21 }
22
23 printk("Found device \"%s\", getting sensor data\n", dev->name);
24 return dev;
25}
26
27void main(void)
28{
29 const struct device *dev = get_bme280_device();
30
31 if (dev == NULL) {
32 return;
33 }
34
35 while (1) {
36 struct sensor_value temp, press, humidity;
37
38 sensor_sample_fetch(dev);
39 sensor_channel_get(dev, SENSOR_CHAN_AMBIENT_TEMP, &temp);
40 sensor_channel_get(dev, SENSOR_CHAN_PRESS, &press);
41 sensor_channel_get(dev, SENSOR_CHAN_HUMIDITY, &humidity);
42
43 printk("temp: %d.%06d; press: %d.%06d; humidity: %d.%06d\n",
44 temp.val1, temp.val2, press.val1, press.val2,
45 humidity.val1, humidity.val2);
46
47 k_sleep(K_MSEC(1000));
48 }
49}
Configuration and Attributes
Setting the communication bus and address is considered the most basic configuration for sensor devices. This setting is done at compile time, via the configuration menu. If the sensor supports interrupts, the interrupt lines and triggering parameters described below are also configured at compile time.
Alongside these communication parameters, sensor chips typically expose multiple parameters that control the accuracy and frequency of measurement. In compliance with Zephyr’s design goals, most of these values are statically configured at compile time.
However, certain parameters could require runtime configuration, for example, threshold values for interrupts. These values are configured via attributes. The example in the following section showcases a sensor with an interrupt line that is triggered when the temperature crosses a threshold. The threshold is configured at runtime using an attribute.
Triggers
Triggers in Zephyr refer to the interrupt lines of the sensor chips. Many sensor chips support one or more triggers. Some examples of triggers include: new data is ready for reading, a channel value has crossed a threshold, or the device has sensed motion.
To configure a trigger, an application needs to supply a
sensor_trigger
and a handler function. The structure contains the
trigger type and the channel on which the trigger must be configured.
Because most sensors are connected via SPI or I2C busses, it is not possible to communicate with them from the interrupt execution context. The execution of the trigger handler is deferred to a thread, so that data fetching operations are possible. A driver can spawn its own thread to fetch data, thus ensuring minimum latency. Alternatively, multiple sensor drivers can share a system-wide thread. The shared thread approach increases the latency of handling interrupts but uses less memory. You can configure which approach to follow for each driver. Most drivers can entirely disable triggers resulting in a smaller footprint.
The following example contains a trigger fired whenever temperature crosses the 26 degree Celsius threshold. It also samples the temperature every second. A real application would ideally disable periodic sampling in the interest of saving power. Since the application has direct access to the kernel config symbols, no trigger is registered when triggering was disabled by the driver’s configuration.
1
2#define UCEL_PER_CEL 1000000
3#define UCEL_PER_MCEL 1000
4#define TEMP_INITIAL_CEL 25
5#define TEMP_WINDOW_HALF_UCEL 500000
6
7static const char *now_str(void)
8{
9 static char buf[16]; /* ...HH:MM:SS.MMM */
10 uint32_t now = k_uptime_get_32();
11 unsigned int ms = now % MSEC_PER_SEC;
12 unsigned int s;
13 unsigned int min;
14 unsigned int h;
15
16 now /= MSEC_PER_SEC;
17 s = now % 60U;
18 now /= 60U;
19 min = now % 60U;
20 now /= 60U;
21 h = now;
22
23 snprintf(buf, sizeof(buf), "%u:%02u:%02u.%03u",
24 h, min, s, ms);
25 return buf;
26}
27
28#ifdef CONFIG_MCP9808_TRIGGER
29
30static struct sensor_trigger trig;
31
32static int set_window(const struct device *dev,
33 const struct sensor_value *temp)
34{
35 const int temp_ucel = temp->val1 * UCEL_PER_CEL + temp->val2;
36 const int low_ucel = temp_ucel - TEMP_WINDOW_HALF_UCEL;
37 const int high_ucel = temp_ucel + TEMP_WINDOW_HALF_UCEL;
38 struct sensor_value val = {
39 .val1 = low_ucel / UCEL_PER_CEL,
40 .val2 = low_ucel % UCEL_PER_CEL,
41 };
42 int rc = sensor_attr_set(dev, SENSOR_CHAN_AMBIENT_TEMP,
43 SENSOR_ATTR_LOWER_THRESH, &val);
44 if (rc == 0) {
45 val.val1 = high_ucel / UCEL_PER_CEL,
46 val.val2 = high_ucel % UCEL_PER_CEL,
47 rc = sensor_attr_set(dev, SENSOR_CHAN_AMBIENT_TEMP,
48 SENSOR_ATTR_UPPER_THRESH, &val);
49 }
50
51 if (rc == 0) {
52 printf("Alert on temp outside [%d, %d] milli-Celsius\n",
53 low_ucel / UCEL_PER_MCEL,
54 high_ucel / UCEL_PER_MCEL);
55 }
56
57 return rc;
58}
59
60static inline int set_window_ucel(const struct device *dev,
61 int temp_ucel)
62{
63 struct sensor_value val = {
64 .val1 = temp_ucel / UCEL_PER_CEL,
65 .val2 = temp_ucel % UCEL_PER_CEL,
66 };
67
68 return set_window(dev, &val);
69}
70
71static void trigger_handler(const struct device *dev,
72 const struct sensor_trigger *trig)
73{
74 struct sensor_value temp;
75 static size_t cnt;
76 int rc;
77
78 ++cnt;
79 rc = sensor_sample_fetch(dev);
80 if (rc != 0) {
81 printf("sensor_sample_fetch error: %d\n", rc);
82 return;
83 }
84 rc = sensor_channel_get(dev, SENSOR_CHAN_AMBIENT_TEMP, &temp);
85 if (rc != 0) {
86 printf("sensor_channel_get error: %d\n", rc);
87 return;
88 }
89
90 printf("trigger fired %u, temp %g deg C\n", cnt,
91 sensor_value_to_double(&temp));
92 set_window(dev, &temp);
93}
94#endif
95
96void main(void)
97{
98 const struct device *dev = DEVICE_DT_GET_ANY(microchip_mcp9808);
99 int rc;
100
101 if (dev == NULL) {
102 printf("Device not found.\n");
103 return;
104 }
105 if (!device_is_ready(dev)) {
106 printf("Device %s is not ready.\n", dev->name);
107 return;
108 }
109
110#ifdef CONFIG_MCP9808_TRIGGER
111 rc = set_window_ucel(dev, TEMP_INITIAL_CEL * UCEL_PER_CEL);
112 if (rc == 0) {
113 trig.type = SENSOR_TRIG_THRESHOLD;
114 trig.chan = SENSOR_CHAN_AMBIENT_TEMP;
115 rc = sensor_trigger_set(dev, &trig, trigger_handler);
116 }
117
118 if (rc != 0) {
119 printf("Trigger set failed: %d\n", rc);
120 return;
121 }
122 printk("Trigger set got %d\n", rc);
123#endif
124
125 while (1) {
126 struct sensor_value temp;
127
128 rc = sensor_sample_fetch(dev);
129 if (rc != 0) {
130 printf("sensor_sample_fetch error: %d\n", rc);
131 break;
132 }
133
134 rc = sensor_channel_get(dev, SENSOR_CHAN_AMBIENT_TEMP, &temp);
135 if (rc != 0) {
136 printf("sensor_channel_get error: %d\n", rc);
137 break;
138 }
139
140 printf("%s: %g C\n", now_str(),
141 sensor_value_to_double(&temp));
142
143 k_sleep(K_SECONDS(2));
144 }
145}
API Reference
- group sensor_interface
Sensor Interface.
Defines
-
SENSOR_G
The value of gravitational constant in micro m/s^2.
-
SENSOR_PI
The value of constant PI in micros.
Typedefs
-
typedef void (*sensor_trigger_handler_t)(const struct device *dev, const struct sensor_trigger *trigger)
Callback API upon firing of a trigger.
- Param dev
Pointer to the sensor device
- Param trigger
The trigger
-
typedef int (*sensor_attr_set_t)(const struct device *dev, enum sensor_channel chan, enum sensor_attribute attr, const struct sensor_value *val)
Callback API upon setting a sensor’s attributes.
See sensor_attr_set() for argument description
-
typedef int (*sensor_attr_get_t)(const struct device *dev, enum sensor_channel chan, enum sensor_attribute attr, struct sensor_value *val)
Callback API upon getting a sensor’s attributes.
See sensor_attr_get() for argument description
-
typedef int (*sensor_trigger_set_t)(const struct device *dev, const struct sensor_trigger *trig, sensor_trigger_handler_t handler)
Callback API for setting a sensor’s trigger and handler.
See sensor_trigger_set() for argument description
-
typedef int (*sensor_sample_fetch_t)(const struct device *dev, enum sensor_channel chan)
Callback API for fetching data from a sensor.
See sensor_sample_fetch() for argument description
-
typedef int (*sensor_channel_get_t)(const struct device *dev, enum sensor_channel chan, struct sensor_value *val)
Callback API for getting a reading from a sensor.
See sensor_channel_get() for argument description
Enums
-
enum sensor_channel
Sensor channels.
Values:
-
enumerator SENSOR_CHAN_ACCEL_X
Acceleration on the X axis, in m/s^2.
-
enumerator SENSOR_CHAN_ACCEL_Y
Acceleration on the Y axis, in m/s^2.
-
enumerator SENSOR_CHAN_ACCEL_Z
Acceleration on the Z axis, in m/s^2.
-
enumerator SENSOR_CHAN_ACCEL_XYZ
Acceleration on the X, Y and Z axes.
-
enumerator SENSOR_CHAN_GYRO_X
Angular velocity around the X axis, in radians/s.
-
enumerator SENSOR_CHAN_GYRO_Y
Angular velocity around the Y axis, in radians/s.
-
enumerator SENSOR_CHAN_GYRO_Z
Angular velocity around the Z axis, in radians/s.
-
enumerator SENSOR_CHAN_GYRO_XYZ
Angular velocity around the X, Y and Z axes.
-
enumerator SENSOR_CHAN_MAGN_X
Magnetic field on the X axis, in Gauss.
-
enumerator SENSOR_CHAN_MAGN_Y
Magnetic field on the Y axis, in Gauss.
-
enumerator SENSOR_CHAN_MAGN_Z
Magnetic field on the Z axis, in Gauss.
-
enumerator SENSOR_CHAN_MAGN_XYZ
Magnetic field on the X, Y and Z axes.
-
enumerator SENSOR_CHAN_DIE_TEMP
Device die temperature in degrees Celsius.
-
enumerator SENSOR_CHAN_AMBIENT_TEMP
Ambient temperature in degrees Celsius.
-
enumerator SENSOR_CHAN_PRESS
Pressure in kilopascal.
-
enumerator SENSOR_CHAN_PROX
Proximity. Adimensional. A value of 1 indicates that an object is close.
-
enumerator SENSOR_CHAN_HUMIDITY
Humidity, in percent.
-
enumerator SENSOR_CHAN_LIGHT
Illuminance in visible spectrum, in lux.
-
enumerator SENSOR_CHAN_IR
Illuminance in infra-red spectrum, in lux.
-
enumerator SENSOR_CHAN_RED
Illuminance in red spectrum, in lux.
-
enumerator SENSOR_CHAN_GREEN
Illuminance in green spectrum, in lux.
-
enumerator SENSOR_CHAN_BLUE
Illuminance in blue spectrum, in lux.
-
enumerator SENSOR_CHAN_ALTITUDE
Altitude, in meters
-
enumerator SENSOR_CHAN_PM_1_0
1.0 micro-meters Particulate Matter, in ug/m^3
-
enumerator SENSOR_CHAN_PM_2_5
2.5 micro-meters Particulate Matter, in ug/m^3
-
enumerator SENSOR_CHAN_PM_10
10 micro-meters Particulate Matter, in ug/m^3
-
enumerator SENSOR_CHAN_DISTANCE
Distance. From sensor to target, in meters
-
enumerator SENSOR_CHAN_CO2
CO2 level, in parts per million (ppm)
-
enumerator SENSOR_CHAN_VOC
VOC level, in parts per billion (ppb)
-
enumerator SENSOR_CHAN_GAS_RES
Gas sensor resistance in ohms.
-
enumerator SENSOR_CHAN_VOLTAGE
Voltage, in volts
-
enumerator SENSOR_CHAN_CURRENT
Current, in amps
-
enumerator SENSOR_CHAN_POWER
Power in watts
-
enumerator SENSOR_CHAN_RESISTANCE
Resistance , in Ohm
-
enumerator SENSOR_CHAN_ROTATION
Angular rotation, in degrees
-
enumerator SENSOR_CHAN_POS_DX
Position change on the X axis, in points.
-
enumerator SENSOR_CHAN_POS_DY
Position change on the Y axis, in points.
-
enumerator SENSOR_CHAN_POS_DZ
Position change on the Z axis, in points.
-
enumerator SENSOR_CHAN_RPM
Revolutions per minute, in RPM.
-
enumerator SENSOR_CHAN_GAUGE_VOLTAGE
Voltage, in volts
-
enumerator SENSOR_CHAN_GAUGE_AVG_CURRENT
Average current, in amps
-
enumerator SENSOR_CHAN_GAUGE_STDBY_CURRENT
Standy current, in amps
-
enumerator SENSOR_CHAN_GAUGE_MAX_LOAD_CURRENT
Max load current, in amps
-
enumerator SENSOR_CHAN_GAUGE_TEMP
Gauge temperature
-
enumerator SENSOR_CHAN_GAUGE_STATE_OF_CHARGE
State of charge measurement in %
-
enumerator SENSOR_CHAN_GAUGE_FULL_CHARGE_CAPACITY
Full Charge Capacity in mAh
-
enumerator SENSOR_CHAN_GAUGE_REMAINING_CHARGE_CAPACITY
Remaining Charge Capacity in mAh
-
enumerator SENSOR_CHAN_GAUGE_NOM_AVAIL_CAPACITY
Nominal Available Capacity in mAh
-
enumerator SENSOR_CHAN_GAUGE_FULL_AVAIL_CAPACITY
Full Available Capacity in mAh
-
enumerator SENSOR_CHAN_GAUGE_AVG_POWER
Average power in mW
-
enumerator SENSOR_CHAN_GAUGE_STATE_OF_HEALTH
State of health measurement in %
-
enumerator SENSOR_CHAN_GAUGE_TIME_TO_EMPTY
Time to empty in minutes
-
enumerator SENSOR_CHAN_GAUGE_TIME_TO_FULL
Time to full in minutes
-
enumerator SENSOR_CHAN_GAUGE_CYCLE_COUNT
Cycle count (total number of charge/discharge cycles)
-
enumerator SENSOR_CHAN_GAUGE_DESIGN_VOLTAGE
Design voltage of cell in V (max voltage)
-
enumerator SENSOR_CHAN_GAUGE_DESIRED_VOLTAGE
Desired voltage of cell in V (nominal voltage)
-
enumerator SENSOR_CHAN_GAUGE_DESIRED_CHARGING_CURRENT
Desired charging current in mA
-
enumerator SENSOR_CHAN_ALL
All channels.
-
enumerator SENSOR_CHAN_COMMON_COUNT
Number of all common sensor channels.
-
enumerator SENSOR_CHAN_PRIV_START = SENSOR_CHAN_COMMON_COUNT
This and higher values are sensor specific. Refer to the sensor header file.
-
enumerator SENSOR_CHAN_MAX = INT16_MAX
Maximum value describing a sensor channel type.
-
enumerator SENSOR_CHAN_ACCEL_X
-
enum sensor_trigger_type
Sensor trigger types.
Values:
-
enumerator SENSOR_TRIG_TIMER
Timer-based trigger, useful when the sensor does not have an interrupt line.
-
enumerator SENSOR_TRIG_DATA_READY
Trigger fires whenever new data is ready.
-
enumerator SENSOR_TRIG_DELTA
Trigger fires when the selected channel varies significantly. This includes any-motion detection when the channel is acceleration or gyro. If detection is based on slope between successive channel readings, the slope threshold is configured via the SENSOR_ATTR_SLOPE_TH and SENSOR_ATTR_SLOPE_DUR attributes.
-
enumerator SENSOR_TRIG_NEAR_FAR
Trigger fires when a near/far event is detected.
-
enumerator SENSOR_TRIG_THRESHOLD
Trigger fires when channel reading transitions configured thresholds. The thresholds are configured via the SENSOR_ATTR_LOWER_THRESH, SENSOR_ATTR_UPPER_THRESH, and SENSOR_ATTR_HYSTERESIS attributes.
-
enumerator SENSOR_TRIG_TAP
Trigger fires when a single tap is detected.
-
enumerator SENSOR_TRIG_DOUBLE_TAP
Trigger fires when a double tap is detected.
-
enumerator SENSOR_TRIG_FREEFALL
Trigger fires when a free fall is detected.
-
enumerator SENSOR_TRIG_COMMON_COUNT
Number of all common sensor triggers.
-
enumerator SENSOR_TRIG_PRIV_START = SENSOR_TRIG_COMMON_COUNT
This and higher values are sensor specific. Refer to the sensor header file.
-
enumerator SENSOR_TRIG_MAX = INT16_MAX
Maximum value describing a sensor trigger type.
-
enumerator SENSOR_TRIG_TIMER
-
enum sensor_attribute
Sensor attribute types.
Values:
-
enumerator SENSOR_ATTR_SAMPLING_FREQUENCY
Sensor sampling frequency, i.e. how many times a second the sensor takes a measurement.
-
enumerator SENSOR_ATTR_LOWER_THRESH
Lower threshold for trigger.
-
enumerator SENSOR_ATTR_UPPER_THRESH
Upper threshold for trigger.
-
enumerator SENSOR_ATTR_SLOPE_TH
Threshold for any-motion (slope) trigger.
-
enumerator SENSOR_ATTR_SLOPE_DUR
Duration for which the slope values needs to be outside the threshold for the trigger to fire.
-
enumerator SENSOR_ATTR_HYSTERESIS
-
enumerator SENSOR_ATTR_OVERSAMPLING
Oversampling factor
-
enumerator SENSOR_ATTR_FULL_SCALE
Sensor range, in SI units.
-
enumerator SENSOR_ATTR_OFFSET
The sensor value returned will be altered by the amount indicated by offset: final_value = sensor_value + offset.
-
enumerator SENSOR_ATTR_CALIB_TARGET
Calibration target. This will be used by the internal chip’s algorithms to calibrate itself on a certain axis, or all of them.
-
enumerator SENSOR_ATTR_CONFIGURATION
Configure the operating modes of a sensor.
-
enumerator SENSOR_ATTR_CALIBRATION
Set a calibration value needed by a sensor.
-
enumerator SENSOR_ATTR_FEATURE_MASK
Enable/disable sensor features
-
enumerator SENSOR_ATTR_ALERT
Alert threshold or alert enable/disable
-
enumerator SENSOR_ATTR_COMMON_COUNT
Number of all common sensor attributes.
-
enumerator SENSOR_ATTR_PRIV_START = SENSOR_ATTR_COMMON_COUNT
This and higher values are sensor specific. Refer to the sensor header file.
-
enumerator SENSOR_ATTR_MAX = INT16_MAX
Maximum value describing a sensor attribute type.
-
enumerator SENSOR_ATTR_SAMPLING_FREQUENCY
Functions
-
int sensor_attr_set(const struct device *dev, enum sensor_channel chan, enum sensor_attribute attr, const struct sensor_value *val)
Set an attribute for a sensor.
- Parameters
dev – Pointer to the sensor device
chan – The channel the attribute belongs to, if any. Some attributes may only be set for all channels of a device, depending on device capabilities.
attr – The attribute to set
val – The value to set the attribute to
- Returns
0 if successful, negative errno code if failure.
-
int sensor_attr_get(const struct device *dev, enum sensor_channel chan, enum sensor_attribute attr, struct sensor_value *val)
Get an attribute for a sensor.
- Parameters
dev – Pointer to the sensor device
chan – The channel the attribute belongs to, if any. Some attributes may only be set for all channels of a device, depending on device capabilities.
attr – The attribute to get
val – Pointer to where to store the attribute
- Returns
0 if successful, negative errno code if failure.
-
static inline int sensor_trigger_set(const struct device *dev, const struct sensor_trigger *trig, sensor_trigger_handler_t handler)
Activate a sensor’s trigger and set the trigger handler.
The handler will be called from a thread, so I2C or SPI operations are safe. However, the thread’s stack is limited and defined by the driver. It is currently up to the caller to ensure that the handler does not overflow the stack.
- Function properties (list may not be complete)
- Parameters
dev – Pointer to the sensor device
trig – The trigger to activate
handler – The function that should be called when the trigger fires
- Returns
0 if successful, negative errno code if failure.
-
int sensor_sample_fetch(const struct device *dev)
Fetch a sample from the sensor and store it in an internal driver buffer.
Read all of a sensor’s active channels and, if necessary, perform any additional operations necessary to make the values useful. The user may then get individual channel values by calling sensor_channel_get.
Since the function communicates with the sensor device, it is unsafe to call it in an ISR if the device is connected via I2C or SPI.
- Parameters
dev – Pointer to the sensor device
- Returns
0 if successful, negative errno code if failure.
-
int sensor_sample_fetch_chan(const struct device *dev, enum sensor_channel type)
Fetch a sample from the sensor and store it in an internal driver buffer.
Read and compute compensation for one type of sensor data (magnetometer, accelerometer, etc). The user may then get individual channel values by calling sensor_channel_get.
This is mostly implemented by multi function devices enabling reading at different sampling rates.
Since the function communicates with the sensor device, it is unsafe to call it in an ISR if the device is connected via I2C or SPI.
- Parameters
dev – Pointer to the sensor device
type – The channel that needs updated
- Returns
0 if successful, negative errno code if failure.
-
int sensor_channel_get(const struct device *dev, enum sensor_channel chan, struct sensor_value *val)
Get a reading from a sensor device.
Return a useful value for a particular channel, from the driver’s internal data. Before calling this function, a sample must be obtained by calling sensor_sample_fetch or sensor_sample_fetch_chan. It is guaranteed that two subsequent calls of this function for the same channels will yield the same value, if sensor_sample_fetch or sensor_sample_fetch_chan has not been called in the meantime.
For vectorial data samples you can request all axes in just one call by passing the specific channel with _XYZ suffix. The sample will be returned at val[0], val[1] and val[2] (X, Y and Z in that order).
- Parameters
dev – Pointer to the sensor device
chan – The channel to read
val – Where to store the value
- Returns
0 if successful, negative errno code if failure.
-
static inline int32_t sensor_ms2_to_g(const struct sensor_value *ms2)
Helper function to convert acceleration from m/s^2 to Gs.
- Parameters
ms2 – A pointer to a sensor_value struct holding the acceleration, in m/s^2.
- Returns
The converted value, in Gs.
-
static inline void sensor_g_to_ms2(int32_t g, struct sensor_value *ms2)
Helper function to convert acceleration from Gs to m/s^2.
- Parameters
g – The G value to be converted.
ms2 – A pointer to a sensor_value struct, where the result is stored.
-
static inline int32_t sensor_rad_to_degrees(const struct sensor_value *rad)
Helper function for converting radians to degrees.
- Parameters
rad – A pointer to a sensor_value struct, holding the value in radians.
- Returns
The converted value, in degrees.
-
static inline void sensor_degrees_to_rad(int32_t d, struct sensor_value *rad)
Helper function for converting degrees to radians.
- Parameters
d – The value (in degrees) to be converted.
rad – A pointer to a sensor_value struct, where the result is stored.
-
static inline double sensor_value_to_double(const struct sensor_value *val)
Helper function for converting struct sensor_value to double.
- Parameters
val – A pointer to a sensor_value struct.
- Returns
The converted value.
-
static inline void sensor_value_from_double(struct sensor_value *val, double inp)
Helper function for converting double to struct sensor_value.
- Parameters
val – A pointer to a sensor_value struct.
inp – The converted value.
-
struct sensor_value
- #include <sensor.h>
Representation of a sensor readout value.
The value is represented as having an integer and a fractional part, and can be obtained using the formula val1 + val2 * 10^(-6). Negative values also adhere to the above formula, but may need special attention. Here are some examples of the value representation:
0.5: val1 = 0, val2 = 500000 -0.5: val1 = 0, val2 = -500000 -1.0: val1 = -1, val2 = 0 -1.5: val1 = -1, val2 = -500000
-
struct sensor_trigger
- #include <sensor.h>
Sensor trigger spec.
Public Members
-
enum sensor_trigger_type type
Trigger type.
-
enum sensor_channel chan
Channel the trigger is set on.
-
enum sensor_trigger_type type
-
struct sensor_driver_api
- #include <sensor.h>
-
SENSOR_G