FIFO README
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@ -16,7 +16,7 @@ A C89 driver for the 3-axis accelerometer LIS3DH. Supports both I2C and SPI.
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## Examples
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See the `examples/` dir for complete code examples
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See the `examples/` dir for complete code examples and explanations of LIS3DH terminology
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## Implementation
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This driver requires the user to implement the following interface functions:
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@ -3,16 +3,22 @@
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### file: simple.c
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Basic example of how to use this device
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### file: fifo.c
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# FIFO
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Instead of polling for every single [x y z] set, a FIFO with programmable capacity ("watermark") can be used, and then dumped into memory once full.
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All FIFO readings use 10-bit resolution regardless of the mode set in `cfg.mode`.
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The watermark level can be adjusted to a value [1-32] (0 disables FIFO) by modifying the `cfg.fifo.size` property before calling `lis3dh_configure()`.
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The LIS3DH can optionally apply a HP filter on the sampling to reduce 'static acceleration' from the data.
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The FIFO "engine" samples/appends another set of [x y z] values at 1/ODR. The maximum ODR supported by the FIFO "engine" is 200 Hz.
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| FIFO mode | symbol | description |
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|------------------|-----------------------|----------------------------|
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| Bypass | `LIS3DH_FIFO_MODE_BYPASS` | FIFO is inoperational |
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| FIFO | `LIS3DH_FIFO_MODE_FIFO` | FIFO can be read/emptied at any time but once overrun has to be reset. See file: `fifo-mode-fifo.c` |
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| Stream | `LIS3DH_FIFO_MODE_STREAM` | FIFO continously writes new data at 1/ODR and will overwrite old data until it is read/emptied. See file: `fifo-mode-stream.c` |
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| Stream_to_FIFO | `LIS3DH_FIFO_STREAM_TO_FIFO` | FIFO behaves like Stream mode until a set interrupt is activated, then changes to a mode FIFO. |
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Note: it seems that the highest data rate (ODR) possible using FIFO is 200 Hz, faster than that and it does not want to restart after 1 FIFO buffer. To sample faster, such as at the advertised 5 KHz rate, you have to use `lis3dh_read()` with `LP` mode.
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### file: interrupts.c
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This device supports two different interrupt "output pins," `INT1` and `INT2`. The appropriate flag must be set in either `cfg.pin1` or `cfg.pin2` and the interrupt source must be configured to trigger into `INT1` or `INT2`.
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example/fifo-mode-stream.c
Normal file
48
example/fifo-mode-stream.c
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#define _GNU_SOURCE
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#include <unistd.h>
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#include <stdio.h>
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#include "lis3dh.h"
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#include "i2c.h"
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#include "interrupt.h"
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#define GPIO_INTERRUPT_PIN_INT1 12
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int main() {
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lis3dh_t lis;
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struct lis3dh_fifo_data fifo;
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int i;
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lis.dev.init = i2c_init;
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lis.dev.read = i2c_read;
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lis.dev.write = i2c_write;
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lis.dev.sleep = usleep;
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lis.dev.deinit = i2c_deinit;
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lis3dh_init(&lis);
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lis3dh_reset(&lis);
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int_register(GPIO_INTERRUPT_PIN_INT1);
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lis.cfg.mode = LIS3DH_MODE_HR;
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lis.cfg.range = LIS3DH_FS_2G;
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lis.cfg.rate = LIS3DH_ODR_100_HZ;
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lis.cfg.pin1.overrun = 1;
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lis.cfg.fifo.mode = LIS3DH_FIFO_MODE_STREAM;
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lis.cfg.fifo.trig = LIS3DH_FIFO_TRIG_INT1;
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lis3dh_configure(&lis);
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for ( ;; ) {
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int_poll(GPIO_INTERRUPT_PIN_INT1);
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lis3dh_read_fifo(&lis, &fifo);
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for(i=0; i<fifo.size; i++)
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printf("x: %4.4d mg, y: %4.4d mg, z: %4.4d mg\n", fifo.x[i], fifo.y[i], fifo.z[i]);
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printf("fifo.size=%d\n", fifo.size);
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}
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lis3dh_deinit(&lis);
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return 0;
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}
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@ -1,56 +0,0 @@
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#define _GNU_SOURCE
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#include <unistd.h>
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#include <stdio.h>
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#include "lis3dh.h"
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#include "i2c.h"
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int main() {
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lis3dh_t lis;
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struct lis3dh_fifo_data fifo;
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int i;
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lis.dev.init = i2c_init;
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lis.dev.read = i2c_read;
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lis.dev.write = i2c_write;
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lis.dev.sleep = usleep;
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lis.dev.deinit = i2c_deinit;
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/* initialise LIS3DH struct */
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if (lis3dh_init(&lis)) {
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/* error handling */
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}
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/* reset device just in case */
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if (lis3dh_reset(&lis)) {
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/* error handling */
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}
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lis.cfg.mode = LIS3DH_MODE_HR;
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lis.cfg.range = LIS3DH_FS_4G;
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lis.cfg.rate = LIS3DH_ODR_100_HZ;
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lis.cfg.fifo.mode = LIS3DH_FIFO_MODE_NORMAL;
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/* write device config */
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if (lis3dh_configure(&lis)) {
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/* error handling */
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}
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/* read as many [x y z] sets as specified by watermark level (size) default (max/32) */
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/* copy them to the fifo data struct `fifo' */
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if (lis3dh_read_fifo(&lis, &fifo)) {
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/* error handling */
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}
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/* read out fifo buffer data */
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for(i=0; i<fifo.size; i++) {
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printf("x: %d mg, y: %d mg, z: %d mg\n", fifo.x[i], fifo.y[i], fifo.z[i]);
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}
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/* deinitialise struct */
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if (lis3dh_deinit(&lis)) {
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/* error handling */
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}
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return 0;
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}
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@ -1,88 +0,0 @@
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#define _GNU_SOURCE
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#include <stdio.h>
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#include <stdlib.h>
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#include <unistd.h>
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#include <math.h>
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#include "lis3dh.h"
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#include "interrupt.h"
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#include "i2c.h"
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/* GPIO 12 or Pin 32 */
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#define GPIO_INTERRUPT_PIN 12
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int main() {
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lis3dh_t lis;
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struct lis3dh_fifo_data fifo;
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int i;
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lis.dev.init = i2c_init;
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lis.dev.read = i2c_read;
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lis.dev.write = i2c_write;
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lis.dev.sleep = usleep;
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lis.dev.deinit = i2c_deinit;
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/* initalise LIS3DH struct */
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if (lis3dh_init(&lis)) {
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/* error handling */
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}
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/* reset device just in case */
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if (lis3dh_reset(&lis)) {
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/* error handling */
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}
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/* register interrupt */
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if (int_register(GPIO_INTERRUPT_PIN)) {
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/* error handling */
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}
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lis.cfg.mode = LIS3DH_MODE_NORMAL;
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lis.cfg.range = LIS3DH_FS_2G;
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lis.cfg.rate = LIS3DH_ODR_100_HZ;
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lis.cfg.fifo.mode = LIS3DH_FIFO_MODE_STREAM;
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lis.cfg.fifo.trig = LIS3DH_FIFO_TRIG_INT1; /* trigger interrupt into int pin1 */
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lis.cfg.pin1.overrun = 1; /* trigger upon FIFO overrun */
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/* set up HP filter to remove DC component */
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lis.cfg.filter.mode = LIS3DH_FILTER_MODE_NORMAL_REF;
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lis.cfg.filter.cutoff = LIS3DH_FILTER_CUTOFF_4;
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lis.cfg.filter.fds = 0; /* remove this line, or set to 1 to enable filter */
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/* write device config */
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if (lis3dh_configure(&lis)) {
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/* error handling */
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}
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/* read REFERENCE to set filter to current accel field */
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if (lis3dh_reference(&lis)) {
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/* error handling */
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}
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/* wait for interrupt from LIS3DH */
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if (int_poll(GPIO_INTERRUPT_PIN)) {
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/* error handling */
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}
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/* read as many [x y z] sets as specified by watermark level (size) */
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/* copy them to the fifo data struct given below as `fifo' */
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if (lis3dh_read_fifo(&lis, &fifo)) {
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/* error handling */
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}
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for(i=0; i<fifo.size; i++) {
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printf("x: %d mg, y: %d mg, z: %d mg\n", fifo.x[i], fifo.y[i], fifo.z[i]);
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}
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/* unregister interrupt */
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if (int_unregister(GPIO_INTERRUPT_PIN)) {
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/* error handling */
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}
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/* deinitalise struct */
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if (lis3dh_deinit(&lis)) {
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/* error handling */
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}
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return 0;
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}
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