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ICM (ICM-45605) Example

This example demonstrates how to use the neuralSPOT IMU driver to collect accelerometer, gyroscope, and temperature data from the ICM-45605 sensor on an Ambiq Apollo MCU. It shows both initialization, calibration, and interrupt-driven frame buffering using a user callback.

Contents

examples/icm/
├── src/
│   └── icm.cc         # Main example application
└── README.md          # This file

Description

The imc.cc application configures the ICM-45605 IMU to sample at 50 Hz, performs an initial bias calibration, and then uses a data-ready interrupt to collect a frame of sensor samples. Upon filling the frame buffer, a user callback prints all samples.

This example is based on Ambiq’s Human Activity Recognition (HAR) model, demonstrating how to integrate raw IMU data into higher‑level AI workflows.

Prerequisites

  • NeuralSPOT SDK (with neuralspot/ns-imu module)

  • Valid hardware setup:

  • Apollo510 EVB

  • ICM-45605 Mikroe Board (MIKRO-6040)
  • J13 jumper selecting 3.3v

Building and Running the Example

  1. Flash the Firmware

 make EXAMPLE=experiments/icm && make EXAMPLE=experiments/icm TARGET=icm deploy && make view
2. Monitor Output

  • On reset, you should see:

    Ready to test IMC
NS_IMU: Calibrating ICM-45605
IMU Init Success
Frame available
Frame 0: Accel: 0.00 0.00 1.00, Gyro: 0.00 0.00 0.00, Temp: 25.00
Frame 1: ...
    * Each Frame available indicates the buffer is ready.

Code Walkthrough

  1. Callback Definition

void my_frame_available_cb(void *arg) {
    ns_imu_config_t *cfg = (ns_imu_config_t *)arg;
    for (int i = 0; i < cfg->frame_size; i++) {
        // Print each sample
    }
}
2. Configuration Structure

ns_imu_config_t imu_cfg = {
    .api               = &ns_imu_V1_0_0,
    .sensor            = NS_IMU_SENSOR_ICM45605,
    .iom               = 0,                    // SPI0
    .accel_fsr         = ACCEL_CONFIG0_ACCEL_UI_FS_SEL_4_G,
    .gyro_fsr          = GYRO_CONFIG0_GYRO_UI_FS_SEL_2000_DPS,
    .accel_odr         = ACCEL_CONFIG0_ACCEL_ODR_50_HZ,
    .gyro_odr          = GYRO_CONFIG0_GYRO_ODR_50_HZ,
    .accel_ln_bw       = IPREG_SYS2_REG_131_ACCEL_UI_LPFBW_DIV_4,
    .gyro_ln_bw        = IPREG_SYS1_REG_172_GYRO_UI_LPFBW_DIV_4,
    .calibrate         = true,                // perform bias calibration
    .frame_available_cb= my_frame_available_cb,
    .frame_size        = 20,                  // number of samples per interrupt
    .frame_buffer      = imu_frame
};
3. Initialization & Main Loop

ns_core_init(...);
ns_power_config(...);
ns_set_performance_mode(...);
ns_imu_configure(&imu_cfg);

while (1) {
  ns_deep_sleep();  // wake on IMU interrupt
}

Troubleshooting

  • No ***********Frame available*********** messages:

  • Check SPI wiring and chip select wiring.

  • Ensure the mikrobus power selector (J13) is set to 3.3v.

  • Incorrect sensor readings:

  • Keep board stationary during calibration.

  • Verify calibrate = true in config.

  • Build errors:

  • Confirm include paths and linking of inv_imu_driver.c.

For more details on the IMU driver API, see neuralspot/ns-imu/includes-api/ns_imu.h.