138 lines
6.8 KiB
Markdown
138 lines
6.8 KiB
Markdown
# lis3dh/example
|
|
|
|
The LIS3DH has 3 operating modes.
|
|
| mode | symbol | description |
|
|
|------|---------|------------|
|
|
| LP | `LIS3DH_MODE_LP` | Low-power mode. 8-bit acc. reading resolution. |
|
|
| Normal | `LIS3DH_MODE_NORMAL` | "Normal" mode. 10-bit acc. reading resolution. |
|
|
| HR | `LIS3DH_MODE_HR` | High-resolution mode. 12-bit acc. reading resolution. |
|
|
|
|
There are serveral `ODR` (internal data/sample rate) options, but some may only be used in a specific operating mode.
|
|
| ODR | mode | symbol |
|
|
|-----|------|--------|
|
|
| 1 Hz | any | `LIS3DH_ODR_1_HZ` |
|
|
| 10 Hz | any | `LIS3DH_ODR_10_HZ` |
|
|
| 25 Hz | any | `LIS3DH_ODR_25_HZ` |
|
|
| 50 Hz | any | `LIS3DH_ODR_50_HZ` |
|
|
| 100 Hz | any | `LIS3DH_ODR_100_HZ` |
|
|
| 200 Hz | any | `LIS3DH_ODR_200_HZ` |
|
|
| 400 Hz | any | `LIS3DH_ODR_400_HZ` |
|
|
| 1344 Hz | Normal | `LIS3DH_ODR_NORM_1344_HZ` |
|
|
| 1600 Hz | LP | `LIS3DH_ODR_LP_1600_HZ` |
|
|
| 5376 Hz | LP | `LIS3DH_ODR_LP_5376_HZ` |
|
|
|
|
### file: simple.c
|
|
Basic example of how to use this device
|
|
|
|
# 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 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 files: `fifo-int-ovrn.c`, `fifo-int-wtm.c`, `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 files: `stream-int-ovrn.c`, `stream-int-wtm.c`, `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: FIFO will not trigger a watermark interrupt (`pin1.wtm`) if the FIFO size is default (32; maximum size). To use the watermark interrupt, the FIFO size has to be between [1-31]. An overrun interrupt (`pin1.overrun`) will always trigger when the FIFO is full, regardless of programmed capacity.
|
|
|
|
Note: to sample data faster than 200 Hz, it is necessary to use the regular data polling functionality using `lis3dh_read()` with the appropriate configuration. See files `simple.c` and `fast.c` for examples.
|
|
|
|
### file: single-click.c
|
|
|
|
Set up single-click detection (no latching interrupt possible)
|
|
|
|
### file: double-click.c
|
|
|
|
Set up double-click detection (no latching interrupt possible)
|
|
|
|
### file: adc.c
|
|
|
|
Enable and read built-in ADCs.
|
|
|
|
> - Input range: 800 mV to 1600 mV
|
|
> - Resolution: 8-bit in LP mode, 10-bit in normal and in HR mode.
|
|
> - Sampling frequency: same as ODR
|
|
|
|
### file: temp.c
|
|
|
|
Enable and read built-in temperature sensor
|
|
|
|
> - Operating range: -40 to 85°C
|
|
> - Step size: ±1°C
|
|
|
|
### Inertial interrupts
|
|
|
|
There are two interrupt registers, `int1` and `int2` that can be configured for inertial interrupts. The config structs are identical and contain the fields: `zh`, `zl`, `yh`, `yl`, `xh`, `xl`, and more. `zh` stands for `Z_axis_high` and `zl` stands for `Z_axis_low`. If both are enabled, the device will generate an interrupt upon Z-axis acceleration exceeding `threshold`, or upon Z-axis acceleration reading at or below `-threshold` (in OR mode. Not possible in AND mode).
|
|
|
|
|
|
| aoi | en_6d | interrupt mode |
|
|
|-----|-------|-------------------------|
|
|
| 0 | 0 | OR combination |
|
|
| 0 | 1 | 6d MOVEMENT recognition |
|
|
| 1 | 0 | AND combination |
|
|
| 1 | 1 | 6d POSITION recognition |
|
|
|
|
|
|
#### OR combination
|
|
|
|
An interrupt is generated when at least one of the configured axes is at or above the threshold level.
|
|
|
|
#### 6D MOVEMENT recognition
|
|
|
|
An interrupt is generated when the device moves from a direction (known or unknown) to a different known direction. The interrupt is only active for 1/ODR.
|
|
|
|
#### AND combination
|
|
|
|
An interrupt is generated when all of the configures axes are at or above the threshold level.
|
|
|
|
#### 6D POSITION recognition
|
|
|
|
An interrupt is generated when the device is "stable" in a known direction. The interrupt is active as long as the direction is maintained.
|
|
|
|
### file: inertial-wakeup.c
|
|
|
|
Inertial interrupt example in OR mode (easily changed to AND mode) with configurable axes, threshold and minimum acceleration duration.
|
|
|
|
### file: free-fall.c
|
|
|
|
Inertial interrupt example activating upon free-fall. It works by using an AND mode interrupt of all the negative axes and comparing them to a threshold value (in the case of negative axis the threshold is multiplied by -1), recommended to be at 350mg (for >30 ms) and activating when the experienced negative acceleration is greater (abs. sense) than the negative threshold.
|
|
|
|
### file: 6d-movement.c
|
|
|
|
Inertial interrupt example, generates an interrupt when some acceleration, `threshold` is experienced on any configured axis for `duration` time. Supposedly the device knows what a "known" direction is.
|
|
|
|
### file: 6d-position.c
|
|
|
|
Inertial interrupt example, the interrupt line is kept active so long as the device is stable (ie acceleration on configured axes does not exceed `threshold` for `duration` time).
|
|
|
|
---
|
|
|
|
### 4D detection
|
|
|
|
4D detection is a subset of 6D detection meant for detecting portrait/landscape screen rotations on mobile phones, etc. It functionally works the same as the 6D modes, except that detection along the Z-axis is disabled.
|
|
|
|
### file: 4d-movement.c
|
|
|
|
Inertial interrupt example, generates an interrupt when some acceleration, `threshold` is experienced on any configured axis for `duration` time. Supposedly the device knows what a "known" direction is.
|
|
|
|
### file: 4d-position.c
|
|
|
|
Inertial interrupt example, the interrupt line is kept active so long as the device is stable (ie acceleration on configured axes does not exceed `threshold` for `duration` time).
|
|
|
|
# "Sleep to Wake" and "Return to Sleep"
|
|
|
|
The LIS3DH can be programmed to automatically switch to `LP` mode upon recognition of a specific event. Once the event is over, the device will return to whatever mode it was in before the event.
|
|
|
|
When the experienced acceleration [OR combination of all axes] falls below the `threshold` value stored in `cfg.act_ths`, the device automatically switches to `LP` mode with an ODR of 10 Hz. The duration of "normal function", the Wake period duration, is specified in `cfg.act_dur`.
|
|
|
|
As soon as the experienced acceleration rises above the threshold, the device restores the original mode and ODR.
|
|
|
|
See file: `sleep-to-wake.c`. |