ICM-20948 9-Axis MEMS Motion Tracking Sensor Driver

C Driver for the IC-20948 9-Axis Telemetry sensor. This driver can be included directly into a developers source or a static library can be created and then linked against. Development is done on the dev branch, and official releases can be found on the master branch. Releases will be made on a ~monthly basis assuming no driver breaking bugs are found. Otherwise, a fix will be released to master ASAP.

Currently supported features

The currently supported features are below. The API is written to greatly simplify the implementation of this IC, and thus only a small amount of control is given to the end-user. In the future, settings/config will be added to allow a user to change sample rates, resolution and more for each sensor in this part.
Currently supported features:

• Accel
  • +-2G
  • +-4G
  • +-8G
  • +-16G
• Gyro
  • +-250DPS
  • +-500DPS
  • +-1000DPS
  • +-2000DPS

Retrieving the Source

The source is located on Github and can be either downloaded and included directly into a developers source OR the developer can add this repo as a submodule into their project directory (The latter is the preferred method).

To include the driver as a git submodule

$ cd ./${DIR_WHERE_YOU_WANT_TO_ADD_THE_MODULE}
$ git submodule add https://github.com/stephendpmurphy/icm20948.git

Integration

Creating & Linking against a static library

To create a static library to link against, you must first source your build environment and ensure the CC environment variable is set to your desired toolchain. Below is an example of sourcing the AVR toolchain before compiling.

$ export CC=/usr/bin/avr-gcc
$ export CXX=/usr/bin/avr-g++

Once your cross-compiler is properly setup. Execute the following commands:

$ mkdir build && cd build
$ cmake ..
$ make

The output library (lib_icm20948.a) can be found in the lib/ folder. Link against this file, and include the icm20948_api.h header file into your source include directories.

#include "icm20948_api.h"

Adding to your own source/project

The other option for integrating the source into your project, is to include everything directly into your project

• Set your include directories to both the inc/ and src/ folders.
• Add the icm20948.c to your source list to be compiled.
• Include the API header file wherever you intended to implement the driver source.

#include "icm20948_api.h"

Implementing the driver

After following the integration steps above, you are ready to implement the driver and start retrieving telemetry data. An example main.c can be found in the templates folder that shows how to implement the init, settings, and data retrieval API. Note that you will need to fill out your own usr_ functions for reading, writing, and a uS delay. You can build the example main.c by first compiling the static lib following the steps in the "Creating & Linking against a static library" and then executing the following commands.

$ cd template
$ mkdir build && cd build
$ cmake ..
$ make

Example application and main can be found below:

#include <stdint.h>
#include "icm20948_api.h"

int8_t usr_write(uint8_t addr, uint8_t *data, uint32_t len) {
    icm20948_return_code_t ret = ICM20948_RET_OK;

    // Assert the CS

    // Write the address

    // Write the data from the provided data buffer

    // De-assert the CS

    return ret;
}

int8_t usr_read(uint8_t addr, uint8_t *data, uint32_t len) {
    icm20948_return_code_t ret = ICM20948_RET_OK;

    // Assert the CS

    // Write your data

    // Read out the data, placing the result in the data buffer

    // De-assert the CS

    return ret;
}

void usr_delay_us(uint32_t period) {
    // uS Delay for the requested period
}

int main(void) {
    icm20948_return_code_t ret = ICM20948_RET_OK;
    icm20948_settings_t settings;
    icm20948_gyro_t gyro_data;
    icm20948_accel_t accel_data;

    // Init the device function pointers
    ret = icm20948_init(usr_read, usr_write, usr_delay_us);

    // Check if we successfully stored the function poiners provided
    if( ret == ICM20948_RET_OK ) {
        // Enable the Gyro
        settings.gyro.en = ICM20948_MOD_ENABLED;
        // Select the +-20000dps range
        settings.gyro.fs = ICM20948_GYRO_FS_SEL_2000DPS;
        // Enable the Accel
        settings.accel.en = ICM20948_MOD_ENABLED;
        // Select the +-2G range
        settings.accel.fs = ICM20948_ACCEL_FS_SEL_2G;
        ret = icm20948_applySettings(&settings);
    }

    while(1) {
        // Retrieve the Gyro data and store it in our gyro_data struct
        // Output is in dps (Degress per second)
        ret |= icm20948_getGyroData(&gyro_data);
        // Retrieve the Accel data and store it in our accel_data struct
        // Output is in mG
        ret |= icm20948_getAccelData(&accel_data);
    }

    return 0;
}

License

License has been provided with this source and can be found in the License file.