The documentation describes the ADXL345 driver, IIO interface, interface usage and configuration. Signed-off-by: Lothar Rubusch <l.rubusch@xxxxxxxxx> --- Documentation/iio/adxl345.rst | 418 ++++++++++++++++++++++++++++++++++ Documentation/iio/index.rst | 1 + 2 files changed, 419 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..8ee01b8b87f4 --- /dev/null +++ b/Documentation/iio/adxl345.rst @@ -0,0 +1,418 @@ +.. 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 +------------- + +Specific IIO events are triggered by their corresponding interrupts. The sensor +driver supports either none or a single active interrupt (INT) line, selectable +from the two available options: INT1 or INT2. The active INT line should be +specified in the device tree. If no INT line is configured, the sensor defaults +to FIFO bypass mode, where event detection is disabled and only X, Y, and Z axis +measurements are available. + +The table below lists the ADXL345-related device files located in the +device-specific path: ``/sys/bus/iio/devices/iio:deviceX/events``. +Note that activity and inactivity detection are DC-coupled by default; +therefore, only the AC-coupled activity and inactivity events are explicitly +listed. + ++---------------------------------------------+---------------------------------------------+ +| 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_adaptive_rising_en | Enable AC coupled activity on X axis | ++---------------------------------------------+---------------------------------------------+ +| in_accel_mag_adaptive_falling_period | AC coupled inactivity time in seconds | ++---------------------------------------------+---------------------------------------------+ +| in_accel_mag_adaptive_falling_value | AC coupled inactivity threshold in 62.5/LSB | ++---------------------------------------------+---------------------------------------------+ +| in_accel_mag_adaptive_rising_value | AC coupled activity threshold in 62.5/LSB | ++---------------------------------------------+---------------------------------------------+ +| in_accel_mag_rising_en | Enable activity detection on X axis | ++---------------------------------------------+---------------------------------------------+ +| 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&y&z_mag_falling_en | Enable inactivity detection on all axis | ++---------------------------------------------+---------------------------------------------+ +| in_accel_x&y&z_mag_adaptive_falling_en | Enable AC coupled inactivity on all axis | ++---------------------------------------------+---------------------------------------------+ +| in_accel_y_gesture_singletap_en | Enable single tap detection on Y axis | ++---------------------------------------------+---------------------------------------------+ +| in_accel_z_gesture_singletap_en | Enable single tap detection on Z axis | ++---------------------------------------------+---------------------------------------------+ + +Please refer to the sensor's datasheet for a detailed description of this +functionality. + +Manually setting the **ODR** will cause the driver to estimate default values +for inactivity detection timing, where higher ODR values correspond to longer +default wait times, and lower ODR values to shorter ones. If these defaults do +not meet your application’s needs, you can explicitly configure the inactivity +wait time. Setting this value to 0 will revert to the default behavior. + +When changing the **g range** configuration, the driver attempts to estimate +appropriate activity and inactivity thresholds by scaling the default values +based on the ratio of the previous range to the new one. The resulting threshold +will never be zero and will always fall between 1 and 255, corresponding to up +to 62.5 g/LSB as specified in the datasheet. However, you can override these +estimated thresholds by setting explicit values. + +When **activity** and **inactivity** events are enabled, the driver +automatically manages hysteresis behavior by setting the **link** and +**auto-sleep** bits. The link bit connects the activity and inactivity +functions, so that one follows the other. The auto-sleep function puts the +sensor into sleep mode when inactivity is detected, reducing power consumption +to the sub-12.5 Hz rate. + +In DC-coupled mode, the current acceleration magnitude is directly compared to +the values in the THRESH_ACT and THRESH_INACT registers to determine activity or +inactivity. In contrast, AC-coupled activity detection uses the acceleration +value at the start of detection as a reference point, and subsequent samples are +compared against this reference. While DC-coupling is the default mode-comparing +live values to fixed thresholds-AC-coupling relies on an internal filter +relative to the configured threshold. + +AC and DC coupling modes are configured separately for activity and inactivity +detection, but only one mode can be active at a time for each. For example, if +AC-coupled activity detection is enabled and then DC-coupled mode is set, only +DC-coupled activity detection will be active. In other words, only the most +recent configuration is applied. + +**Single tap** detection can be configured per the datasheet by setting the +threshold and duration parameters. When only single tap detection is enabled, +the single tap interrupt triggers as soon as the acceleration exceeds the +threshold (marking the start of the duration) and then falls below it, provided +the duration limit is not exceeded. If both single tap and double tap detections +are enabled, the single tap interrupt is triggered only after the double tap +event has been either confirmed or dismissed. + +To configure **double tap** detection, you must also set the window and latency +parameters in microseconds (µs). The latency period begins once the single tap +signal drops below the threshold and acts as a waiting time during which any +spikes are ignored for double tap detection. After the latency period ends, the +detection window starts. If the acceleration rises above the threshold and then +falls below it again within this window, a double tap event is triggered upon +the fall below the threshold. + +Double tap event detection is thoroughly explained in the datasheet. After a +single tap event is detected, a double tap event may follow, provided the signal +meets certain criteria. However, double tap detection can be invalidated for +three reasons: + +* If the **suppress bit** is set, any acceleration spike above the tap + threshold during the tap latency period immediately invalidates the double tap + detection. In other words, no spikes are allowed during latency when the + suppress bit is active. + +* The double tap event is invalid if the acceleration is above the threshold at + the start of the double tap window. + +* Double tap detection is also invalidated if the acceleration duration exceeds + the limit set by the duration register. + +For double tap detection, the same duration applies as for single tap: the +acceleration must rise above the threshold and then fall below it within the +specified duration. Note that the suppress bit is typically enabled when double +tap detection is active. + +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 formula: + +.. 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_adaptive_rising_value + + ## AC coupled inactivity, threshold, [62.5/LSB] + root:/sys/bus/iio/devices/iio:device0> echo 4 > ./events/in_accel_mag_adaptive_falling_value + + ## AC coupled inactivity, time [s] + root:/sys/bus/iio/devices/iio:device0> echo 3 > ./events/in_accel_mag_adaptive_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 + + ## AC coupled activity, enable + root:/sys/bus/iio/devices/iio:device0> echo 1 > ./events/in_accel_mag_adaptive_rising_en + + ## AC coupled inactivity, enable + root:/sys/bus/iio/devices/iio:device0> echo 1 > ./events/in_accel_x\&y\&z_mag_adaptive_falling_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. diff --git a/Documentation/iio/index.rst b/Documentation/iio/index.rst index 2d6afc5a8ed5..c333720c1c9f 100644 --- a/Documentation/iio/index.rst +++ b/Documentation/iio/index.rst @@ -32,6 +32,7 @@ Industrial I/O Kernel Drivers adis16480 adis16550 adxl380 + adxl345 bno055 ep93xx_adc opt4060 -- 2.39.5
