Wiki

Below is the source of this page. To edit this source as well as other pages on the wiki, you must login.
====== ADXL372 Input 3-Axis Digital Accelerometer Linux Driver ======

===== Supported Devices =====

  * [[adi>ADXL372]]

===== Evaluation Boards =====

  * [[adi>EVAL-ADXL372Z]] 

===== Description =====

This is a Linux industrial I/O ([[software:linux:docs:iio:iio|IIO]]) subsystem driver, targeting dual or quad channel serial interface ADCs.
The industrial I/O subsystem provides a unified framework for drivers for many different types of converters and sensors using a number of different physical interfaces (i2c, spi, etc). 
See [[software:linux:docs:iio:iio|IIO]] for more information.

====== Source Code ======

===== Status =====

^ Source ^ Mainlined? ^
| [[git.linux.org>drivers/iio/accel/adxl372.c|git]] | [[git.linux.org>drivers/iio/accel/adxl372.c|Yes]]  |

===== Files =====

^ Function ^ File ^
| core driver | [[linux.github>master?drivers/iio/accel/adxl372.c | drivers/iio/accel/adxl372.c]] |
| spi driver | [[linux.github>master?drivers/iio/accel/adxl372_spi.c | drivers/iio/accel/adxl372_spi.c]] |
| i2c driver | [[linux.github>master?drivers/iio/accel/adxl372_i2c.c | drivers/iio/accel/adxl372_i2c.c]] |
| header | [[linux.github>master?drivers/iio/iio/accel/adxl372.h | drivers/iio/accel/adxl372.h]] |
| Documentation | [[linux.github>master?Documentation/devicetree/bindings/iio/accel/adxl345.txt | adxl345.txt]] |
| ABI documentation| [[linux.github>master?Documentation/ABI/testing/sysfs-bus-iio-accel-adxl372 | sysfs-bus-iio-accel-adxl372]] |

Example device tree

^ Function ^ File ^
| dts  | [[linux.github>rpi-4.19.y?arch/arm/boot/dts/overlays/rpi-adxl372-overlay.dts | rpi-adxl372-overlay.dts]] |

====== Example platform device initialization ======

Required devicetree properties:
  * compatible: Needs to be the name of the device. E.g. "adi,adxl372"
  * reg: the I2C address or SPI chip select number for the device

Required properties for SPI bus usage:
  * spi-max-frequency: Maximum SPI clock frequency.

Optional properties:
  * interrupts: a list of interrupt specifiers

Example for a SPI device node:
<code>
	#address-cells = <1>;
	#size-cells = <0>;
	status = "okay";

	adxl372@0 {
		compatible = "adi,adxl372";
		reg = <0>;
		spi-max-frequency = <1000000>;
		interrupts = <25 2>;
		interrupt-parent = <&gpio>;
	};
</code>

Example for a I2C device node:
<code>
	#address-cells = <1>;
	#size-cells = <0>;
	status = "okay";

	adxl372@53 {
		compatible = "adi,adxl372";
		reg = <0x53>;
		interrupts = <25 2>;
		interrupt-parent = <&gpio>;
	};
</code>

====== Driver testing ======

<WRAP box bggreen><wrap info>This specifies any shell prompt running on the target</wrap>
<xterm>
root:/> **cd /sys/bus/iio/devices/**
root:/sys/bus/iio/devices> ls
iio:device0

root:/sys/bus/iio/devices> **cd iio\:device0**

root:/sys/bus/iio/devices/iio:device0> **ls -l**
drwxr-xr-x 2 root root    0 Oct 25 04:25 buffer
-rw-r--r-- 1 root root 4096 Oct 25 04:25 current_timestamp_clock
-r--r--r-- 1 root root 4096 Oct 25 04:25 dev
-rw-r--r-- 1 root root 4096 Oct 25 04:28 in_accel_filter_low_pass_3db_frequency
-r--r--r-- 1 root root 4096 Oct 25 04:25 in_accel_filter_low_pass_3db_frequency_available
-rw-r--r-- 1 root root 4096 Oct 25 04:27 in_accel_sampling_frequency
-rw-r--r-- 1 root root 4096 Oct 25 04:25 in_accel_scale
-rw-r--r-- 1 root root 4096 Oct 25 04:25 in_accel_x_raw
-rw-r--r-- 1 root root 4096 Oct 25 04:25 in_accel_y_raw
-rw-r--r-- 1 root root 4096 Oct 25 04:25 in_accel_z_raw
-r--r--r-- 1 root root 4096 Oct 25 04:25 name
lrwxrwxrwx 1 root root    0 Oct 25 04:25 of_node -> ../../../../../../../../firmware/devicetree/base/soc/spi@7e204000/adxl372@0
-r--r--r-- 1 root root 4096 Oct 25 04:25 peak_fifo_mode_enable
drwxr-xr-x 2 root root    0 Oct 25 04:25 power
-r--r--r-- 1 root root 4096 Oct 25 04:25 sampling_frequency_available
drwxr-xr-x 2 root root    0 Oct 25 04:25 scan_elements
lrwxrwxrwx 1 root root    0 Oct 25 04:25 subsystem -> ../../../../../../../../bus/iio
drwxr-xr-x 2 root root    0 Oct 25 04:25 trigger
-rw-r--r-- 1 root root 4096 Oct 25 04:25 uevent
</xterm></WRAP>

=== Show device name ===

<WRAP box bggreen><wrap info>This specifies any shell prompt running on the target</wrap>
<xterm>
root:/sys/bus/iio/devices/iio:device0> **cat name**
adxl372
</xterm></WRAP>

=== Show scale ===

**Description:**\\
scale to be applied to in_accel_*_raw in order to obtain the acceleration.

<WRAP box bggreen><wrap info>This specifies any shell prompt running on the target</wrap>
<xterm>
root:/sys/bus/iio/devices/iio:device0> **cat in_accel_scale**
0.958241
</xterm></WRAP>

=== Show axis x measurement ===

**Description:**\\
Raw unscaled acceleration measurement on x axis

<WRAP box bggreen><wrap info>This specifies any shell prompt running on the target</wrap>
<xterm>
root:/sys/bus/iio/devices/iio:device0> **cat in_accel_x_raw**
-5
</xterm></WRAP>

=== Set sampling frequency ===

<WRAP box bggreen><wrap info>This specifies any shell prompt running on the target</wrap>
<xterm>
root:/sys/bus/iio/devices/iio:device0> **cat sampling_frequency_available**
400 800 1600 3200 6400
root:/sys/bus/iio/devices/iio:device0> **cat in_accel_sampling_frequency**
6400
root:/sys/bus/iio/devices/iio:device0> **echo 3200 > in_accel_sampling_frequency**
root:/sys/bus/iio/devices/iio:device0> **cat in_accel_sampling_frequency**
3200
</xterm></WRAP>

=== Show available bandwidths for the current set frequency ===

<WRAP box bggreen><wrap info>This specifies any shell prompt running on the target</wrap>
<xterm>
root:/sys/bus/iio/devices/iio:device0> **cat in_accel_sampling_frequency**
256000
root:/sys/bus/iio/devices/iio:device0> **cat in_accel_filter_low_pass_3db_frequency_available**
200 400 800 1600 3200
root:/sys/bus/iio/devices/iio:device0>
</xterm></WRAP>

=== Change the bandwidth ===

<WRAP box bggreen><wrap info>This specifies any shell prompt running on the target</wrap>
<xterm>
root:/sys/bus/iio/devices/iio:device0> **cat in_accel_filter_low_pass_3db_frequency_available**
200 400 800 1600 3200
root:/sys/bus/iio/devices/iio:device0> **cat in_accel_filter_low_pass_3db_frequency**
3200
root:/sys/bus/iio/devices/iio:device0> **echo 1600 > in_accel_filter_low_pass_3db_frequency**
root:/sys/bus/iio/devices/iio:device0> **cat in_accel_filter_low_pass_3db_frequency**
1600
root:/sys/bus/iio/devices/iio:device0> **echo 3200 > in_accel_sampling_frequency**
root:/sys/bus/iio/devices/iio:device0> **cat in_accel_filter_low_pass_3db_frequency_available**
200 400 800 1600
root:/sys/bus/iio/devices/iio:device0> **echo 1600 > in_accel_sampling_frequency**
root:/sys/bus/iio/devices/iio:device0> **cat in_accel_filter_low_pass_3db_frequency**
800
</xterm></WRAP>

===== Using the FIFO Buffer =====

**Description:**\\
The ADXL372 includes a deep, 512 sample FIFO buffer. The 512 FIFO samples can be allotted in several ways, such as the following:
  * 170 sample sets of concurrent 3-axis data
  * 256 sample sets of concurrent 2-axis data (user selectable)
  * 512 sample sets of single-axis data
  * 170 sets of impact event peak (x, y, z)

==== Trigger management ====

**Description:**\\
The FIFO is configured in **Stream Mode** and **FIFO_FULL** interrupt is enabled. The interrupt will be triggered when the FIFO watermark is reached.

<WRAP box bggreen><wrap info>This specifies any shell prompt running on the target</wrap>
<xterm>
root:/sys/bus/iio/devices/iio:device0> **cat trigger/current_trigger** 
adxl372-dev-*
</xterm></WRAP>

==== Buffer management ====

**Description:**\\
The scan_elements directory contains interfaces for elements that will be captured for a single triggered sample set in the buffer

<WRAP box bggreen><wrap info>This specifies any shell prompt running on the target</wrap>
<xterm>
root:/sys/bus/iio/devices/iio:device0/scan_elements> **ls -l**
-rw-r--r-- 1 root root 4096 Oct 25 08:08 in_accel_x_en
-r--r--r-- 1 root root 4096 Oct 25 08:08 in_accel_x_index
-r--r--r-- 1 root root 4096 Oct 25 08:08 in_accel_x_type
-rw-r--r-- 1 root root 4096 Oct 25 08:08 in_accel_y_en
-r--r--r-- 1 root root 4096 Oct 25 08:08 in_accel_y_index
-r--r--r-- 1 root root 4096 Oct 25 08:08 in_accel_y_type
-rw-r--r-- 1 root root 4096 Oct 25 08:08 in_accel_z_en
-r--r--r-- 1 root root 4096 Oct 25 08:08 in_accel_z_index
-r--r--r-- 1 root root 4096 Oct 25 08:08 in_accel_z_type
-rw-r--r-- 1 root root 4096 Oct 25 08:08 in_timestamp_en
-r--r--r-- 1 root root 4096 Oct 25 08:08 in_timestamp_index
-r--r--r-- 1 root root 4096 Oct 25 08:08 in_timestamp_type
root:/sys/bus/iio/devices/iio:device0/scan_elements>
</xterm></WRAP>

Before enabling the buffer, a few steps need to be completed. 
  * For example, if we want the FIFO to store sample sets of concurrent 3-axis data, we need to enable the scan elements:
<WRAP box bggreen><wrap info>This specifies any shell prompt running on the target</wrap>
<xterm>
root:/sys/bus/iio/devices/iio:device0/scan_elements> **echo 1 > in_accel_x_en**
root:/sys/bus/iio/devices/iio:device0/scan_elements> **echo 1 > in_accel_y_en**
root:/sys/bus/iio/devices/iio:device0/scan_elements> **echo 1 > in_accel_z_en**
</xterm></WRAP>

<WRAP box bggreen><wrap info>This specifies any shell prompt running on the target</wrap>
<xterm>
root:/sys/bus/iio/devices/iio:device0/buffer> ls
**enable** **hwfifo_enabled**  **hwfifo_watermark**  **hwfifo_watermark_max**  **hwfifo_watermark_min**  **length ** **watermark**
root:/sys/bus/iio/devices/iio:device0/buffer>
</xterm></WRAP>

  * Set the buffer length:
<WRAP box bggreen><wrap info>This specifies any shell prompt running on the target</wrap>
<xterm>
root:/sys/bus/iio/devices/iio:device0/buffer> **echo 1024 > length**
</xterm></WRAP>

  * Set the fifo watermak:
Because we enabled all three channels, then the watermark can be set to a maximum of 170 sample sets.
<WRAP box bggreen><wrap info>This specifies any shell prompt running on the target</wrap>
<xterm>
root:/sys/bus/iio/devices/iio:device0/buffer> **echo 170 > watermark**
</xterm></WRAP>

The FIFO can also be configured to store peak acceleration (x, y, and z) for every over-threshold event. This can be done by writing 1 to the **peak_fifo_mode_enable** attribute:
<WRAP box bggreen><wrap info>This specifies any shell prompt running on the target</wrap>
<xterm>
root:/sys/bus/iio/devices/iio:device0> **echo 1 > peak_fifo_mode_enable**
</xterm></WRAP>
Note that this mode can work only if all three axis are enabled.

  * Enable the buffer:
<WRAP box bggreen><wrap info>This specifies any shell prompt running on the target</wrap>
<xterm>
root:/sys/bus/iio/devices/iio:device0/buffer> **echo 1 > enable**
</xterm></WRAP>

To read samples:
<WRAP box bggreen><wrap info>This specifies any shell prompt running on the target</wrap>
<xterm>
root:/sys/bus/iio/devices/iio:device0/buffer> **cat /dev/iio:device0**
</xterm></WRAP>

====== Low level register access via debugfs (direct_reg_access) ======

Some IIO drivers feature an optional debug facility, allowing users to read or write registers directly. Special care needs to be taken when using this feature, since you can modify registers on the back of the driver. Accessing debugfs requires root privileges.

In order to identify if the IIO device in question feature this option you first need to identify the IIO device number.

Therefore read the name attribute of each IIO device

<WRAP box bggreen><wrap info>This specifies any shell prompt running on the target</wrap>
<xterm>
root@analog:~# grep "" /sys/bus/iio/devices/iio\:device*/name
adxl372
root@analog:~# 
</xterm></WRAP>

Change directory to /sys/kernel/debug/iio/iio:deviceX and check if the direct_reg_access file exists.

<WRAP box bggreen><wrap info>This specifies any shell prompt running on the target</wrap>
<xterm>
root@analog:~# cd /sys/kernel/debug/iio/iio\:device0/
root@analog:/sys/kernel/debug/iio/iio:device0# ls direct_reg_access  
ls direct_reg_access
root@analog:/sys/kernel/debug/iio/iio:device0#
</xterm></WRAP>

Reading

<WRAP box bggreen><wrap info>This specifies any shell prompt running on the target</wrap>
<xterm>
root@analog:/sys/kernel/debug/iio/iio:device0# echo 0x0 > direct_reg_access   
  
root@analog:/sys/kernel/debug/iio/iio:device0# cat direct_reg_access 
0xAD
root@analog:/sys/kernel/debug/iio/iio:device0#
</xterm></WRAP>

Writing

Write ADDRESS VALUE

<WRAP box bggreen><wrap info>This specifies any shell prompt running on the target</wrap>
<xterm>
root@analog:/sys/kernel/debug/iio/iio:device0# echo 0x3D 0x80 > direct_reg_access   
root@analog:/sys/kernel/debug/iio/iio:device0# cat direct_reg_access 
0x80
root@analog:/sys/kernel/debug/iio/iio:device0#
</xterm></WRAP>

====== More Information ======

{{page>software:linux:docs:iio:iio_snippets#iio pointers&noheader&firstseconly&noeditbtn}}
Analog Devices Wiki

Page Tools
