william/lis3dh
1
0
Fork 0
Code Issues Pull Requests Projects Releases Wiki Activity

FIFO README

Browse Source
This commit is contained in:
William Clark 2024-01-06 23:44:38 +00:00
parent d0aa9e1137
commit ce05aa49e5
5 changed files with 58 additions and 148 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

2
README.md
View File

@ -16,7 +16,7 @@ A C89 driver for the 3-axis accelerometer LIS3DH. Supports both I2C and SPI.
## Examples
See the `examples/` dir for complete code examples
See the `examples/` dir for complete code examples and explanations of LIS3DH terminology
## Implementation
This driver requires the user to implement the following interface functions:

12
example/README.md
View File

@ -3,16 +3,22 @@
### file: simple.c
Basic example of how to use this device
### file: fifo.c
# FIFO
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.
All FIFO readings use 10-bit resolution regardless of the mode set in `cfg.mode`.
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()`.
The LIS3DH can optionally apply a HP filter on the sampling to reduce 'static acceleration' from the data.
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.
| FIFO mode | symbol | description |
|------------------|-----------------------|----------------------------|
| Bypass | `LIS3DH_FIFO_MODE_BYPASS` | FIFO is inoperational |
| 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` |
| 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` |
| 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. |
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.
### file: interrupts.c
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`.

48
example/fifo-mode-stream.c Normal file
View File

@ -0,0 +1,48 @@
#define _GNU_SOURCE
#include <unistd.h>
#include <stdio.h>
#include "lis3dh.h"
#include "i2c.h"
#include "interrupt.h"
#define GPIO_INTERRUPT_PIN_INT1 12
int main() {
lis3dh_t lis;
struct lis3dh_fifo_data fifo;
int i;
lis.dev.init = i2c_init;
lis.dev.read = i2c_read;
lis.dev.write = i2c_write;
lis.dev.sleep = usleep;
lis.dev.deinit = i2c_deinit;
lis3dh_init(&lis);
lis3dh_reset(&lis);
int_register(GPIO_INTERRUPT_PIN_INT1);
lis.cfg.mode = LIS3DH_MODE_HR;
lis.cfg.range = LIS3DH_FS_2G;
lis.cfg.rate = LIS3DH_ODR_100_HZ;
lis.cfg.pin1.overrun = 1;
lis.cfg.fifo.mode = LIS3DH_FIFO_MODE_STREAM;
lis.cfg.fifo.trig = LIS3DH_FIFO_TRIG_INT1;
lis3dh_configure(&lis);
for ( ;; ) {
int_poll(GPIO_INTERRUPT_PIN_INT1);
lis3dh_read_fifo(&lis, &fifo);
for(i=0; i<fifo.size; i++)
printf("x: %4.4d mg, y: %4.4d mg, z: %4.4d mg\n", fifo.x[i], fifo.y[i], fifo.z[i]);
printf("fifo.size=%d\n", fifo.size);
}
lis3dh_deinit(&lis);
return 0;
}

56
example/fifo.c
View File

@ -1,56 +0,0 @@
#define _GNU_SOURCE
#include <unistd.h>
#include <stdio.h>
#include "lis3dh.h"
#include "i2c.h"
int main() {
lis3dh_t lis;
struct lis3dh_fifo_data fifo;
int i;
lis.dev.init = i2c_init;
lis.dev.read = i2c_read;
lis.dev.write = i2c_write;
lis.dev.sleep = usleep;
lis.dev.deinit = i2c_deinit;
/* initialise LIS3DH struct */
if (lis3dh_init(&lis)) {
/* error handling */
}
/* reset device just in case */
if (lis3dh_reset(&lis)) {
/* error handling */
}
lis.cfg.mode = LIS3DH_MODE_HR;
lis.cfg.range = LIS3DH_FS_4G;
lis.cfg.rate = LIS3DH_ODR_100_HZ;
lis.cfg.fifo.mode = LIS3DH_FIFO_MODE_NORMAL;
/* write device config */
if (lis3dh_configure(&lis)) {
/* error handling */
}
/* read as many [x y z] sets as specified by watermark level (size) default (max/32) */
/* copy them to the fifo data struct `fifo' */
if (lis3dh_read_fifo(&lis, &fifo)) {
/* error handling */
}
/* read out fifo buffer data */
for(i=0; i<fifo.size; i++) {
printf("x: %d mg, y: %d mg, z: %d mg\n", fifo.x[i], fifo.y[i], fifo.z[i]);
}
/* deinitialise struct */
if (lis3dh_deinit(&lis)) {
/* error handling */
}
return 0;
}

88
example/interrupts.c
View File

@ -1,88 +0,0 @@
#define _GNU_SOURCE
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <math.h>
#include "lis3dh.h"
#include "interrupt.h"
#include "i2c.h"
/* GPIO 12 or Pin 32 */
#define GPIO_INTERRUPT_PIN 12
int main() {
lis3dh_t lis;
struct lis3dh_fifo_data fifo;
int i;
lis.dev.init = i2c_init;
lis.dev.read = i2c_read;
lis.dev.write = i2c_write;
lis.dev.sleep = usleep;
lis.dev.deinit = i2c_deinit;
/* initalise LIS3DH struct */
if (lis3dh_init(&lis)) {
/* error handling */
}
/* reset device just in case */
if (lis3dh_reset(&lis)) {
/* error handling */
}
/* register interrupt */
if (int_register(GPIO_INTERRUPT_PIN)) {
/* error handling */
}
lis.cfg.mode = LIS3DH_MODE_NORMAL;
lis.cfg.range = LIS3DH_FS_2G;
lis.cfg.rate = LIS3DH_ODR_100_HZ;
lis.cfg.fifo.mode = LIS3DH_FIFO_MODE_STREAM;
lis.cfg.fifo.trig = LIS3DH_FIFO_TRIG_INT1; /* trigger interrupt into int pin1 */
lis.cfg.pin1.overrun = 1; /* trigger upon FIFO overrun */
/* set up HP filter to remove DC component */
lis.cfg.filter.mode = LIS3DH_FILTER_MODE_NORMAL_REF;
lis.cfg.filter.cutoff = LIS3DH_FILTER_CUTOFF_4;
lis.cfg.filter.fds = 0; /* remove this line, or set to 1 to enable filter */
/* write device config */
if (lis3dh_configure(&lis)) {
/* error handling */
}
/* read REFERENCE to set filter to current accel field */
if (lis3dh_reference(&lis)) {
/* error handling */
}
/* wait for interrupt from LIS3DH */
if (int_poll(GPIO_INTERRUPT_PIN)) {
/* error handling */
}
/* read as many [x y z] sets as specified by watermark level (size) */
/* copy them to the fifo data struct given below as `fifo' */
if (lis3dh_read_fifo(&lis, &fifo)) {
/* error handling */
}
for(i=0; i<fifo.size; i++) {
printf("x: %d mg, y: %d mg, z: %d mg\n", fifo.x[i], fifo.y[i], fifo.z[i]);
}
/* unregister interrupt */
if (int_unregister(GPIO_INTERRUPT_PIN)) {
/* error handling */
}
/* deinitalise struct */
if (lis3dh_deinit(&lis)) {
/* error handling */
}
return 0;
}