Free-Fall Detection Using LIS3DH Freefall Application Interrupt

Prerequisites

Before working with this example, it is helpful to get familiar with the information in Getting Started with STMicroelectronics STM32 Processor Based Boards. This topic provides information about working with the STMicroelectronics CubeMX software for board I/O configuration.

Required Hardware

To run this example, you need this hardware:

Hardware Connection

Hardware Configuration in the Model

Open the the model stnucleo_i2c_lis3dh_autochutetriggering_ec. In the Command Window, type:

open_system('stnucleo_i2c_lis3dh_autochutetriggering_ec.slx');

The model is preconfigured to work with STM32F767Zi board. If you are using a different STMicroelectronics STM32 processor based board, change the hardware board by performing the following steps:

1. Navigate to Modeling > Model Settings to open the Configuration Parameters dialog box.

2. Open the Hardware Implementation pane, and from the Hardware board list, select the STMicroelectronics STM32 processor based board that you are using.

3. Click Apply. Click OK to close the dialog box.

Configure the Free-fall Detection on LIS3DH for Interrupt Service Routine (ISR)

1. In the model, open the External Interrupt block, and ensure that the parameters are set as shown. The LIS3DH sensor block is placed in the Initialize Function subsystem.

2. This example includes an STM32 CubeMX project file i2c_lis3dh_freefall.ioc that configures I/O connections for code generation. As shown in Getting Started with STMicroelectronics STM32 Processor Based Boards, you can browse to the project file from the Configuration Parameters dialog box. Or, you could use the STM32 CubeMX software to create a project file. Launch the STM32CubeMX project in the STM32CubeMX tool and apply configurations to enable to GPIO as shown in STM32 CubeMX.

3. In STM32 processor based boards, for the I2C calls to work from within ISR, the interrupt priority of the external interrupt must be modified. The interrupt priority is modified using the System Outputs block. In this example, since PE11 is configured as the external interrupt, NVIC_SetPriority(EXTI4_IRQn,0xFF); is added to the System Outputs block. The IRQn can vary with respect to targets and pins. You can modify the IRQn based on the pin and target selection.

Ensure that the Free-fall is selected for Detect parameter and also ensure that Generate Interrupt parameter is selected and INT1 is selected for Interrupt pin.

4. Perform the following configurations to enable and configure I2C1 to enable the communication between host and target as shown in STM32 CubeMX.

Initiate Monitor and Tune Action for the Model

During Monitor and Tune action, the model is deployed as a C code on the hardware. The code obtains real-time data from the hardware. The data acquisition and parameter tuning are done while the application is running on the hardware.

1. On the Hardware tab, in the Mode section, select Run on board (External Mode) and then click Monitor & Tune.

The lower-left corner of the model window displays status while Simulink prepares, downloads, and runs the Simulink model on the hardware. During simulation, the pin PE11 on STMicroelectronics STM32 processor based board generates an interrupt on every rising edge of the signal, which triggers the function-call subsystem.

2. In the example, the threshold is set to 7.0 m/s^2 so the setup has to be dropped from a distance of 1m above the ground. If the threshold is lowered, increase the drop height appropriately.

Close Model

bdclose('stnucleo_i2c_lis3dh_autochutetriggering_ec.slx');