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neuralSPOT IMU Driver Library

This library provides a lightweight wrapper around the ICM-45605 IMU sensor and other supported IMUs, making it easy to initialize, configure, calibrate, and read 6‑degree‑of‑freedom (6DOF) data on Ambiq Apollo MCUs.

Table of Contents

  1. Features
  2. Installation
  3. Quick Start
  4. Configuration Options
  5. APIs
  6. Code Examples
  7. Polling Example
  8. Interrupt‑Driven Example
  9. Calibration
  10. Versioning and Compatibility
  11. License

Features

  • Easy SPI initialization for ICM-45605 IMU
  • Automatic soft reset and FSR/ODR configuration
  • Built‑in calibration routine for accel and gyro biases
  • Optional data‑ready interrupt support with frame buffering
  • Simple C API for embedded real‑time applications

Installation

  1. Clone the neuralSPOT repository:
git clone https://github.com/AmbiqAI/neuralSPOT.git

  1. Add the neuralspot/ns-imu folder to your build system include path.

  2. Link against ns-imu/src/ns_imu.c, ns_imu_icm45605_driver.c, and other core source files.

Quick Start

  1. Include the API header:
#include "ns_imu.h"
  1. Declare and configure ns_imu_config_t:
ns_imu_config_t imu_cfg = {
  .api               = &ns_imu_current_version,
  .sensor            = NS_IMU_SENSOR_ICM45605,
  .iom               = 0,                             // SPI port
  .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,                          // run calibration
  .frame_available_cb= NULL,                          // polling mode
  .frame_size        = 0,
  .frame_buffer      = NULL
};

ns_imu_sensor_data_t imu_data;
  1. Initialize core and power rails, then configure IMU:
NS_TRY(ns_core_init(&core_cfg), "Core init failed.");
NS_TRY(ns_power_config(&ns_development_default), "Power init failed.");
NS_TRY(ns_set_performance_mode(NS_MINIMUM_PERF), "Perf mode failed.");

if (ns_imu_configure(&imu_cfg) != NS_STATUS_SUCCESS) {
    ns_lp_printf("IMU init failed\n");
}
  1. Read data in your loop:
while (1) {
  if (ns_imu_get_data(&imu_cfg, &imu_data) == NS_STATUS_SUCCESS) {
      ns_lp_printf("Accel: %f, %f, %f | Gyro: %f, %f, %f\n",
          imu_data.accel_g[0], imu_data.accel_g[1], imu_data.accel_g[2],
          imu_data.gyro_dps[0], imu_data.gyro_dps[1], imu_data.gyro_dps[2]);
  }
  ns_delay_us(20000); // 50 Hz polling
}

Configuration Options

Field Description
sensor IMU sensor type (NS_IMU_SENSOR_ICM45605)
iom SPI/I2C instance
accel_fsr Accel full‑scale range (e.g., 4 G)
gyro_fsr Gyro full‑scale range (e.g., 2000 dps)
accel_odr Accel output data rate (e.g., 50 Hz)
gyro_odr Gyro output data rate
accel_ln_bw, gyro_ln_bw Low‑noise bandwidth dividers
calibrate Enable built‑in calibration
frame_available_cb Data‑ready callback (NULL for polling)
frame_size Number of samples per frame
frame_buffer Buffer pointer for interrupt-driven samples

APIs

  • uint32_t ns_imu_configure(ns_imu_config_t *cfg);
  • uint32_t ns_imu_get_data(ns_imu_config_t *cfg, ns_imu_sensor_data_t *data);
  • uint32_t ns_imu_ICM45605_init(ns_imu_config_t *cfg);
  • uint32_t ns_imu_ICM_45606_get_data(ns_imu_config_t *cfg, ns_imu_sensor_data_t *data);
  • uint32_t ns_imu_ICM45605_configure_interrupts(ns_imu_config_t *cfg);
  • uint32_t ns_imu_ICM_45605_handle_interrupt(void);

Refer to ns-imu/includes-api/ns_imu.h and ns_imu_icm45605_driver.h for full signatures.

Code Examples

Polling Example

See examples/imc/src/imc.cc:

ns_imu_configure(&imu_cfg);
while (1) {
  ns_imu_get_data(&imu_cfg, &imu_data);
  // process imu_data
  ns_delay_us(20000);
}

Interrupt‑Driven Example

// Allocate buffer for 20 frames
ns_imu_sensor_data_t imu_frame[20];

void frame_cb(void *arg) {
    ns_imu_config_t *cfg = (ns_imu_config_t *)arg;
    for (int i = 0; i < cfg->frame_size; i++) {
        // handle imu_frame[i]
    }
}

imu_cfg.frame_available_cb = frame_cb;
imu_cfg.frame_size        = 20;
imu_cfg.frame_buffer      = imu_frame;

ns_imu_configure(&imu_cfg);
// MPU will interrupt and call frame_cb internally
while (1) {
  ns_deep_sleep();
}

Calibration

When calibrate = true, the driver averages 250 samples (plus 10 warm‑up) to compute accel/gyro biases. Stationary orientation assumed: accel = [0,0,1g], gyro = [0,0,0].

Versioning and Compatibility

  • Current API: v1.0.0 (NS_IMU_CURRENT_VERSION)
  • Oldest supported: v0.0.1
  • Sensor: ICM-45605

License

Licensed under the Ambiq AI neuralSPOT SDK license. See LICENSE for details.