motion.mcu.icm42670p.driver/icm42670p/imu

Overview

The eMD driver is TDK Invensense's reference code to drive our IMU from a microcontroller-based system. It is coded in C language and organized around modules.

Common files

All modules rely on the following files.

Files:

• imu/inv_imu_transport.h: Definition of the abstraction layer used to communicate with the IMU.
• imu/inv_imu_transport.c: Implementation of the abstraction layer used to communicate with the IMU.
• imu/inv_imu.h: Describes IMU specificities and capabilities.
• imu/inv_imu_regmap_rev_a.h: Exposes register map using positions and masks.
• imu/inv_imu_defs.h: Defines possible values for most used registers.
• imu/inv_imu_extfunc.h: Defines system functions required by the driver, which shall be implemented in the application layer.

Driver

The driver contains the generic functionalities required to operate our IMU.

Depends on:

• Common files

Files:

• imu/inv_imu_driver.h: Definition of the driver API.
• imu/inv_imu_driver.c: Implementation of the driver API.
• imu/inv_imu_version.h: Contains the driver's version as a string.

Self-test

The self-test module contains the code required to operate IMU's self-test.

Depends on:

• Driver
• Common files

Files:

• imu/inv_imu_selftest.h: Definition of the self-test module API.
• imu/inv_imu_selftest.c: Implementation of the self-test module API.

APEX

The APEX module provides API to operate algorithm features (APEX) on-chip. The following features are available:

• Pedometer (step count and step detector)
• FreeFall detection, including Low-G and High-G detection.
• Tilt detection
• Significant Motion Detection

Depends on:

• Driver
• Common files

Files:

• imu/inv_imu_apex.h: Definition of the APEX module API.
• imu/inv_imu_apex.c: Implementation of the APEX module API.

Initializing driver

Please, follow these steps:

• On your application code, create a local variable of type inv_imu_device_t and another one of type inv_imu_serif_t: inv_imu_device_t imu_dev; and inv_imu_serif_t imu_serif;
• Initialize serif structure:
  • Provide an implementation of the read_reg and write_reg functions and initialize the corresponding pointers.
  • Configure the max_read and max_write fields which indicates the maximum numbers of bytes allowed per transaction.
  • Configure the serif_type field which indicates the serial interface used. Available options are listed in inv_imu_transport.h.
  • The context field can be set to 0.
• Initialize sensor event callback pointer in inv_imu_adv_var_t structure. This function will be called when a new sensor data will be available.
• Call the inv_imu_adv_init function, providing the device and serif objects as well as a callback which will be executed when a new sample is received.

Example of initialization in C:

inv_imu_device_t imu_dev;
inv_imu_serif_t  imu_serif;

/* Initialize serial interface */
imu_serif.read_reg   = si_io_imu_read_reg;
imu_serif.write_reg  = si_io_imu_write_reg;
imu_serif.max_read   = 32768;
imu_serif.max_write  = 32768;
imu_serif.serif_type = SERIF_TYPE;
imu_serif.context    = 0;

/* Init device */
rc |= inv_imu_init(&imu_dev, &imu_serif, sensor_event_cb);