| lists.openwall.net | lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC | |
|
Open Source and information security mailing list archives
| ||
|
Message-Id: <20250510224405.17910-8-l.rubusch@gmail.com> Date: Sat, 10 May 2025 22:44:05 +0000 From: Lothar Rubusch <l.rubusch@...il.com> To: lars@...afoo.de, Michael.Hennerich@...log.com, jic23@...nel.org Cc: linux-iio@...r.kernel.org, linux-kernel@...r.kernel.org, eraretuya@...il.com, l.rubusch@...il.com Subject: [PATCH v8 7/7] docs: iio: add documentation for adxl345 driver The documentation describes the ADXL345 driver, IIO interface, interface usage and configuration. Signed-off-by: Lothar Rubusch <l.rubusch@...il.com> --- Documentation/iio/adxl345.rst | 458 ++++++++++++++++++++++++++++++++++ 1 file changed, 458 insertions(+) create mode 100644 Documentation/iio/adxl345.rst diff --git a/Documentation/iio/adxl345.rst b/Documentation/iio/adxl345.rst new file mode 100644 index 000000000000..e21b783153a6 --- /dev/null +++ b/Documentation/iio/adxl345.rst @@ -0,0 +1,458 @@ +.. SPDX-License-Identifier: GPL-2.0 + +=============== +ADXL345 driver +=============== + +This driver supports Analog Device's ADXL345/375 on SPI/I2C bus. + +1. Supported Devices +==================== + +* `ADXL345 <https://www.analog.com/ADXL345>`_ +* `ADXL375 <https://www.analog.com/ADXL375>`_ + +The ADXL345 is a generic purpose low power, 3-axis accelerometer with selectable +measurement ranges. The ADXL345 supports the ±2 g, ±4 g, ±8 g, and ±16 g ranges. + +2. Device Attributes +==================== + +Each IIO device, has a device folder under ``/sys/bus/iio/devices/iio:deviceX``, +where X is the IIO index of the device. Under these folders reside a set of +device files, depending on the characteristics and features of the hardware +device in questions. These files are consistently generalized and documented in +the IIO ABI documentation. + +The following table shows the ADXL345 related device files, found in the +specific device folder path ``/sys/bus/iio/devices/iio:deviceX``. + ++-------------------------------------------+----------------------------------------------------------+ +| 3-Axis Accelerometer related device files | Description | ++-------------------------------------------+----------------------------------------------------------+ +| in_accel_sampling_frequency | Currently selected sample rate. | ++-------------------------------------------+----------------------------------------------------------+ +| in_accel_sampling_frequency_available | Available sampling frequency configurations. | ++-------------------------------------------+----------------------------------------------------------+ +| in_accel_scale | Scale/range for the accelerometer channels. | ++-------------------------------------------+----------------------------------------------------------+ +| in_accel_scale_available | Available scale ranges for the accelerometer channel. | ++-------------------------------------------+----------------------------------------------------------+ +| in_accel_x_calibbias | Calibration offset for the X-axis accelerometer channel. | ++-------------------------------------------+----------------------------------------------------------+ +| in_accel_x_raw | Raw X-axis accelerometer channel value. | ++-------------------------------------------+----------------------------------------------------------+ +| in_accel_y_calibbias | y-axis acceleration offset correction | ++-------------------------------------------+----------------------------------------------------------+ +| in_accel_y_raw | Raw Y-axis accelerometer channel value. | ++-------------------------------------------+----------------------------------------------------------+ +| in_accel_z_calibbias | Calibration offset for the Z-axis accelerometer channel. | ++-------------------------------------------+----------------------------------------------------------+ +| in_accel_z_raw | Raw Z-axis accelerometer channel value. | ++-------------------------------------------+----------------------------------------------------------+ + +Channel Processed Values +------------------------- + +A channel value can be read from its _raw attribute. The value returned is the +raw value as reported by the devices. To get the processed value of the channel, +apply the following formula: + +.. code-block:: bash + + processed value = (_raw + _offset) * _scale + +Where _offset and _scale are device attributes. If no _offset attribute is +present, simply assume its value is 0. + ++-------------------------------------+---------------------------+ +| Channel type | Measurement unit | ++-------------------------------------+---------------------------+ +| Acceleration on X, Y, and Z axis | Meters per second squared | ++-------------------------------------+---------------------------+ + +Sensor Events +------------- + +Particular IIO events will be triggered by the corresponding interrupts. The +sensor driver supports no or one active INT line, where the sensor has two +possible INT IOs. Configure the used INT line in the devicetree. If no INT line +is configured, the sensor falls back to FIFO bypass mode and no events are +possible, only X, Y and Z axis measurements are possible. + +The following table shows the ADXL345 related device files, found in the +specific device folder path ``/sys/bus/iio/devices/iio:deviceX/events``. +Note, the default activity/inactivity is DC coupled. Thus only AC coupled +activity and inactivity are mentioned explicitly. + ++---------------------------------------------+---------------------------------------------+ +| Event handle | Description | ++---------------------------------------------+---------------------------------------------+ +| in_accel_gesture_doubletap_en | Enable double tap detection on all axis | ++---------------------------------------------+---------------------------------------------+ +| in_accel_gesture_doubletap_reset_timeout | Double tap window in [us] | ++---------------------------------------------+---------------------------------------------+ +| in_accel_gesture_doubletap_tap2_min_delay | Double tap latent in [us] | ++---------------------------------------------+---------------------------------------------+ +| in_accel_gesture_singletap_timeout | Single tap duration in [us] | ++---------------------------------------------+---------------------------------------------+ +| in_accel_gesture_singletap_value | Single tap threshold value in 62.5/LSB | ++---------------------------------------------+---------------------------------------------+ +| in_accel_mag_falling_period | Inactivity time in seconds | ++---------------------------------------------+---------------------------------------------+ +| in_accel_mag_falling_value | Inactivity threshold value in 62.5/LSB | ++---------------------------------------------+---------------------------------------------+ +| in_accel_mag_freefall_en | Enable free-fall detection on all axis | ++---------------------------------------------+---------------------------------------------+ +| in_accel_mag_freefall_period | Free-fall detection time in us | ++---------------------------------------------+---------------------------------------------+ +| in_accel_mag_freefall_value | Free-fall threshold value in 62.5/LSB | ++---------------------------------------------+---------------------------------------------+ +| in_accel_mag_referenced_falling_period | AC coupled inactivity time in seconds | ++---------------------------------------------+---------------------------------------------+ +| in_accel_mag_referenced_falling_value | AC coupled inactivity threshold in 62.5/LSB | ++---------------------------------------------+---------------------------------------------+ +| in_accel_mag_referenced_rising_value | AC coupled activity threshold in 62.5/LSB | ++---------------------------------------------+---------------------------------------------+ +| in_accel_mag_rising_value | Activity threshold value in 62.5/LSB | ++---------------------------------------------+---------------------------------------------+ +| in_accel_x_gesture_singletap_en | Enable single tap detection on X axis | ++---------------------------------------------+---------------------------------------------+ +| in_accel_x_mag_referenced_rising_en | Enable AC coupled activity on X axis | ++---------------------------------------------+---------------------------------------------+ +| in_accel_x_mag_rising_en | Enable activity detection on X axis | ++---------------------------------------------+---------------------------------------------+ +| in_accel_x&y&z_mag_falling_en | Enable inactivity detection on all axis | ++---------------------------------------------+---------------------------------------------+ +| in_accel_x&y&z_mag_referenced_falling_en | Enable AC coupled inactivity on all axis | ++---------------------------------------------+---------------------------------------------+ +| in_accel_y_gesture_singletap_en | Enable single tap detection on Y axis | ++---------------------------------------------+---------------------------------------------+ +| in_accel_y_mag_referenced_rising_en | Enable AC coupled activity on Y axis | ++---------------------------------------------+---------------------------------------------+ +| in_accel_y_mag_rising_en | Enable activity detection on Y axis | ++---------------------------------------------+---------------------------------------------+ +| in_accel_z_gesture_singletap_en | Enable single tap detection on Z axis | ++---------------------------------------------+---------------------------------------------+ +| in_accel_z_mag_referenced_rising_en | Enable AC coupled activity on Z axis | ++---------------------------------------------+---------------------------------------------+ +| in_accel_z_mag_rising_en | Enable activity detection on Z axis | ++---------------------------------------------+---------------------------------------------+ + +Find a detailed description of a particular functionality in the sensor +datasheet. + +Setting the **ODR** explicitly will result in estimated adjusted default values +for the inactivity time detection, where higher frequencies shall default to +longer wait periods, and vice versa. It is also possible to explicetly +configure inactivity wait times, if the defaulting approach does not match +application requirements. Setting 0 here, will fall back to default setting. + +The **g range** configuration also tries to estimate activity and inactivity +thresholds when switching to another g range. The default range will be +factorized by the relation of old range divided by new range. The value never +becomes 0 and will be at least 1 and at most 255 i.e. 62.5g/LSB according to +the datasheet. Nevertheless activity and inactivity thresholds can be +overwritten by explicit values. + +When **activity** and **inactivity** events are enabled, the driver automatically +will implement its hysteresis solution by setting link bit and autosleep bit. +The link bit serially links the activity and inactivity functions. On the other +side, the autosleep function switches the sensor to sleep mode if the +inactivity function is enabled. This will reduce current consumption to the +sub-12.5Hz rate. Inactivity time can be configured between 1s and 255s. When 0 +is configured as inactivity time, the driver will define a reasonable value +depending on a heuristic approach to optimize power consumption. + +In **DC-coupled** operation, the current acceleration magnitude is compared +directly with THRESH_ACT and THRESH_INACT registers to determine whether +activity or inactivity was detected. In AC-coupled operation for activity +detection, the acceleration value at the start of activity detection is taken +as a reference value. New samples are then compared to this reference value. +Where DC-coupled is the default case detecting against the configured threshold, +AC-coupled measurements are referenced against an internal filter depending +on the configured threshold. +Activity detection can be enabled on particular axis. Inactivity detection on +the other side, is enabled or disabled on all axis. +Note, AC-coupling and DC-coupling are individually set for activity and/or +inactivity detection, and cannot be set both at the same time. Enabling +AC-coupled activity detection, and then DC-coupled activity detection will +result in performing DC-coupled activity detection only. Hence, only the most +recent configuration will valid. + +**Single tap** detection can be configured according to the datasheet by specifying +threshold and duration. If only the single tap is in use, the single tap +interrupt is triggered when the acceleration goes above threshold (i.e. DUR +start) and below the threshold, as long as duration is not exceeded. If single +tap and double tap are in use, the single tap is triggered when the doulbe tap +event has been either validated or invalidated. + +For **double tap** configure additionally window and latency in [us]. Latency +starts counting when the single tap goes below threshold and is a waiting +period, any spikes here are ignored for double tap detection. After latency, +the window starts. Any rise above threshold, with a consequent fall below +threshold within window time, rises a double tap signal when going below +threshold. + +Double tap event detection is best described in the datasheet. After a +single tap event was detected, a double tap event can be detected. Therefore the +signal must match several criteria, and detection can also considered invalid +for three reasons: +* If the **suppress bit** is set and when still in the tap latency period, any +measurement of acceleration spike above the tap threshold invalidates double tap +detection immediately, i.e. during latency must not occur spikes for double tap +detection when the suppress bit is set. +* A double tap event is considered invalid, if acceleration lies above the +threshold at the start of the window time for double tap. +* Additionally, double tap detection can be considered invalid, if an +acceleration exceeds the time limit for taps, set by duration register. +Note, since for double tap the same duration counts, i.e. when rising above +threshold, a consequent falling below threshold has to be within duration time. +Also note, the suppress bit is generally set when double tap is enabled. + +A **free-fall** event is detected if the measurement signal on all axis goes +below the configured threshold for a configured period of time [us]. It is then +reissued again and again. The generated magnitude event on the IIO channel is +actually the same to the DC-coupled inactivity event. Since both can be +considered as magnitude events on all axis (and'd). When using +activity/inactivity detection and free-fall detection, it is probably the best +approach o combine AC coupled activity/inactivity detection with free-fall. + +In situations with DC coupled activity/inactivity and free-fall enabled, +activity/inactivity indicate the state change of the sensor with far higher +periods [s], than the period taken for free-fall detection [us]. Probably the +only way would be to verify the state change to inactive of the sensor in order +to interprete a inactivity event rather than the typically more often happening +free-fall event. + +Note, that activity/inactivy, as also free-fall is recommended for 12.5 Hz ODR +up to 400 Hz. By the datasheet, free-fall threshold is recommended between 300mg +and 600mg (0x05 to 0x09), and free-fall time is recommended to be set between +100ms and 350ms (0x14 to 0x46). + +Usage Examples +-------------- + +Show device name: + +.. code-block:: bash + + root:/sys/bus/iio/devices/iio:device0> cat name + adxl345 + +Show accelerometer channels value: + +.. code-block:: bash + + root:/sys/bus/iio/devices/iio:device0> cat in_accel_x_raw + -1 + root:/sys/bus/iio/devices/iio:device0> cat in_accel_y_raw + 2 + root:/sys/bus/iio/devices/iio:device0> cat in_accel_z_raw + -253 + +Set calibration offset for accelerometer channels: + +.. code-block:: bash + + root:/sys/bus/iio/devices/iio:device0> cat in_accel_x_calibbias + 0 + + root:/sys/bus/iio/devices/iio:device0> echo 50 > in_accel_x_calibbias + root:/sys/bus/iio/devices/iio:device0> cat in_accel_x_calibbias + 50 + +Given the 13-bit full resolution, the available ranges are calculated by the +following forumla: + +.. code-block:: bash + + (g * 2 * 9.80665) / (2^(resolution) - 1) * 100; for g := 2|4|8|16 + +Scale range configuration: + +.. code-block:: bash + + root:/sys/bus/iio/devices/iio:device0> cat ./in_accel_scale + 0.478899 + root:/sys/bus/iio/devices/iio:device0> cat ./in_accel_scale_available + 0.478899 0.957798 1.915595 3.831190 + + root:/sys/bus/iio/devices/iio:device0> echo 1.915595 > ./in_accel_scale + root:/sys/bus/iio/devices/iio:device0> cat ./in_accel_scale + 1.915595 + +Set output data rate (ODR): + +.. code-block:: bash + + root:/sys/bus/iio/devices/iio:device0> cat ./in_accel_sampling_frequency + 200.000000 + + root:/sys/bus/iio/devices/iio:device0> cat ./in_accel_sampling_frequency_available + 0.097000 0.195000 0.390000 0.781000 1.562000 3.125000 6.250000 12.500000 25.000000 50.000000 100.000000 200.000000 400.000000 800.000000 1600.000000 3200.000000 + + root:/sys/bus/iio/devices/iio:device0> echo 1.562000 > ./in_accel_sampling_frequency + root:/sys/bus/iio/devices/iio:device0> cat ./in_accel_sampling_frequency + 1.562000 + +Configure one or several events: + +.. code-block:: bash + + root:> cd /sys/bus/iio/devices/iio:device0 + + root:/sys/bus/iio/devices/iio:device0> echo 1 > ./buffer0/in_accel_x_en + root:/sys/bus/iio/devices/iio:device0> echo 1 > ./buffer0/in_accel_y_en + root:/sys/bus/iio/devices/iio:device0> echo 1 > ./buffer0/in_accel_z_en + + root:/sys/bus/iio/devices/iio:device0> echo 1 > ./scan_elements/in_accel_x_en + root:/sys/bus/iio/devices/iio:device0> echo 1 > ./scan_elements/in_accel_y_en + root:/sys/bus/iio/devices/iio:device0> echo 1 > ./scan_elements/in_accel_z_en + + root:/sys/bus/iio/devices/iio:device0> echo 14 > ./in_accel_x_calibbias + root:/sys/bus/iio/devices/iio:device0> echo 2 > ./in_accel_y_calibbias + root:/sys/bus/iio/devices/iio:device0> echo -250 > ./in_accel_z_calibbias + + root:/sys/bus/iio/devices/iio:device0> echo 24 > ./buffer0/length + + ## AC coupled activity, threshold [62.5/LSB] + root:/sys/bus/iio/devices/iio:device0> echo 6 > ./events/in_accel_mag_referenced_rising_value + + ## AC coupled inactivity, threshold, [62.5/LSB] + root:/sys/bus/iio/devices/iio:device0> echo 4 > ./events/in_accel_mag_referenced_falling_value + + ## AC coupled inactivity, time [s] + root:/sys/bus/iio/devices/iio:device0> echo 3 > ./events/in_accel_mag_referenced_falling_period + + ## singletap, threshold + root:/sys/bus/iio/devices/iio:device0> echo 35 > ./events/in_accel_gesture_singletap_value + + ## singletap, duration [us] + root:/sys/bus/iio/devices/iio:device0> echo 0.001875 > ./events/in_accel_gesture_singletap_timeout + + ## doubletap, window [us] + root:/sys/bus/iio/devices/iio:device0> echo 0.025 > ./events/in_accel_gesture_doubletap_reset_timeout + + ## doubletap, latent [us] + root:/sys/bus/iio/devices/iio:device0> echo 0.025 > ./events/in_accel_gesture_doubletap_tap2_min_delay + + ## free-fall, threshold [62.5/LSB] + root:/sys/bus/iio/devices/iio:device0> echo 8 > ./events/in_accel_mag_freefall_value + + ## free-fall, time [ms] + root:/sys/bus/iio/devices/iio:device0> echo 1.25 > ./events/in_accel_mag_freefall_period + + ## activity, enable + root:/sys/bus/iio/devices/iio:device0> echo 1 > ./events/in_accel_x_mag_referenced_rising_en + root:/sys/bus/iio/devices/iio:device0> echo 1 > ./events/in_accel_y_mag_referenced_rising_en + root:/sys/bus/iio/devices/iio:device0> echo 1 > ./events/in_accel_z_mag_referenced_rising_en + + ## inactivity, enable + root:/sys/bus/iio/devices/iio:device0> echo 1 > ./events/in_accel_x\&y\&z_mag_referenced_falling_en + + ## free-fall, enable + root:/sys/bus/iio/devices/iio:device0> echo 1 > ./events/in_accel_mag_freefall_en + + ## singletap, enable + root:/sys/bus/iio/devices/iio:device0> echo 1 > ./events/in_accel_x_gesture_singletap_en + root:/sys/bus/iio/devices/iio:device0> echo 1 > ./events/in_accel_y_gesture_singletap_en + root:/sys/bus/iio/devices/iio:device0> echo 1 > ./events/in_accel_z_gesture_singletap_en + + ## doubletap, enable + root:/sys/bus/iio/devices/iio:device0> echo 1 > ./events/in_accel_gesture_doubletap_en + +Verify incoming events: + +.. code-block:: bash + + root:# iio_event_monitor adxl345 + Found IIO device with name adxl345 with device number 0 + Event: time: 1739063415957073383, type: accel(z), channel: 0, evtype: mag, direction: rising + Event: time: 1739063415963770218, type: accel(z), channel: 0, evtype: mag, direction: rising + Event: time: 1739063416002563061, type: accel(z), channel: 0, evtype: gesture, direction: singletap + Event: time: 1739063426271128739, type: accel(x&y&z), channel: 0, evtype: mag, direction: falling + Event: time: 1739063436539080713, type: accel(x&y&z), channel: 0, evtype: mag, direction: falling + Event: time: 1739063438357970381, type: accel(z), channel: 0, evtype: mag, direction: rising + Event: time: 1739063446726161586, type: accel(z), channel: 0, evtype: mag, direction: rising + Event: time: 1739063446727892670, type: accel(z), channel: 0, evtype: mag, direction: rising + Event: time: 1739063446743019768, type: accel(z), channel: 0, evtype: mag, direction: rising + Event: time: 1739063446744650696, type: accel(z), channel: 0, evtype: mag, direction: rising + Event: time: 1739063446763559386, type: accel(z), channel: 0, evtype: gesture, direction: singletap + Event: time: 1739063448818126480, type: accel(x&y&z), channel: 0, evtype: mag, direction: falling + ... + +Activity and inactivity belong together and indicate state changes as follows + +.. code-block:: bash + + root:# iio_event_monitor adxl345 + Found IIO device with name adxl345 with device number 0 + Event: time: 1744648001133946293, type: accel(x), channel: 0, evtype: mag, direction: rising + <after inactivity time elapsed> + Event: time: 1744648057724775499, type: accel(x&y&z), channel: 0, evtype: mag, direction: falling + ... + +3. Device Buffers +================= + +This driver supports IIO buffers. + +All devices support retrieving the raw acceleration and temperature measurements +using buffers. + +Usage examples +-------------- + +Select channels for buffer read: + +.. code-block:: bash + + root:/sys/bus/iio/devices/iio:device0> echo 1 > scan_elements/in_accel_x_en + root:/sys/bus/iio/devices/iio:device0> echo 1 > scan_elements/in_accel_y_en + root:/sys/bus/iio/devices/iio:device0> echo 1 > scan_elements/in_accel_z_en + +Set the number of samples to be stored in the buffer: + +.. code-block:: bash + + root:/sys/bus/iio/devices/iio:device0> echo 10 > buffer/length + +Enable buffer readings: + +.. code-block:: bash + + root:/sys/bus/iio/devices/iio:device0> echo 1 > buffer/enable + +Obtain buffered data: + +.. code-block:: bash + + root:> iio_readdev -b 16 -s 1024 adxl345 | hexdump -d + WARNING: High-speed mode not enabled + 0000000 00003 00012 00013 00005 00010 00011 00005 00011 + 0000010 00013 00004 00012 00011 00003 00012 00014 00007 + 0000020 00011 00013 00004 00013 00014 00003 00012 00013 + 0000030 00004 00012 00013 00005 00011 00011 00005 00012 + 0000040 00014 00005 00012 00014 00004 00010 00012 00004 + 0000050 00013 00011 00003 00011 00012 00005 00011 00013 + 0000060 00003 00012 00012 00003 00012 00012 00004 00012 + 0000070 00012 00003 00013 00013 00003 00013 00012 00005 + 0000080 00012 00013 00003 00011 00012 00005 00012 00013 + 0000090 00003 00013 00011 00005 00013 00014 00003 00012 + 00000a0 00012 00003 00012 00013 00004 00012 00015 00004 + 00000b0 00014 00011 00003 00014 00013 00004 00012 00011 + 00000c0 00004 00012 00013 00004 00014 00011 00004 00013 + 00000d0 00012 00002 00014 00012 00005 00012 00013 00005 + 00000e0 00013 00013 00003 00013 00013 00005 00012 00013 + 00000f0 00004 00014 00015 00005 00012 00011 00005 00012 + ... + +See ``Documentation/iio/iio_devbuf.rst`` for more information about how buffered +data is structured. + +4. IIO Interfacing Tools +======================== + +See ``Documentation/iio/iio_tools.rst`` for the description of the available IIO +interfacing tools. -- 2.39.5
Powered by blists - more mailing lists