flipper-zero-tutorials/js/vgm_sensor/js_vgm/imu.c

#include <furi.h>
#include "imu.h"
#include "ICM42688P/ICM42688P.h"

#define TAG "IMU"

#define ACCEL_GYRO_RATE DataRate100Hz

#define FILTER_SAMPLE_FREQ 100.f
#define FILTER_BETA 0.08f

#define SAMPLE_RATE_DIV 5

#define SENSITIVITY_K 30.f
#define EXP_RATE 1.1f

#define IMU_CALI_AVG 64

typedef enum {
    ImuStop = (1 << 0),
    ImuNewData = (1 << 1),
} ImuThreadFlags;

#define FLAGS_ALL (ImuStop | ImuNewData)

typedef struct {
    float q0;
    float q1;
    float q2;
    float q3;
    float roll;
    float pitch;
    float yaw;
} ImuProcessedData;

typedef struct {
    FuriThread* thread;
    ICM42688P* icm42688p;
    ImuProcessedData processed_data;
    bool lefty;
} ImuThread;

static void imu_madgwick_filter(
    ImuProcessedData* out,
    ICM42688PScaledData* accel,
    ICM42688PScaledData* gyro);

static void imu_irq_callback(void* context) {
    furi_assert(context);
    ImuThread* imu = context;
    furi_thread_flags_set(furi_thread_get_id(imu->thread), ImuNewData);
}

static void imu_process_data(ImuThread* imu, ICM42688PFifoPacket* in_data) {
    ICM42688PScaledData accel_data;
    ICM42688PScaledData gyro_data;

    // Get accel and gyro data in g and degrees/s
    icm42688p_apply_scale_fifo(imu->icm42688p, in_data, &accel_data, &gyro_data);

    // Gyro: degrees/s to rads/s
    gyro_data.x = gyro_data.x / 180.f * M_PI;
    gyro_data.y = gyro_data.y / 180.f * M_PI;
    gyro_data.z = gyro_data.z / 180.f * M_PI;

    // Sensor Fusion algorithm
    ImuProcessedData* out = &imu->processed_data;
    imu_madgwick_filter(out, &accel_data, &gyro_data);

    // Quaternion to euler angles
    float roll = atan2f(
        out->q0 * out->q1 + out->q2 * out->q3, 0.5f - out->q1 * out->q1 - out->q2 * out->q2);
    float pitch = asinf(-2.0f * (out->q1 * out->q3 - out->q0 * out->q2));
    float yaw = atan2f(
        out->q1 * out->q2 + out->q0 * out->q3, 0.5f - out->q2 * out->q2 - out->q3 * out->q3);

    // Euler angles: rads to degrees
    out->roll = roll / M_PI * 180.f;
    out->pitch = pitch / M_PI * 180.f;
    out->yaw = yaw / M_PI * 180.f;
}

static void calibrate_gyro(ImuThread* imu) {
    ICM42688PRawData data;
    ICM42688PScaledData offset_scaled = {.x = 0.f, .y = 0.f, .z = 0.f};

    icm42688p_write_gyro_offset(imu->icm42688p, &offset_scaled);
    furi_delay_ms(10);

    int32_t avg_x = 0;
    int32_t avg_y = 0;
    int32_t avg_z = 0;

    for(uint8_t i = 0; i < IMU_CALI_AVG; i++) {
        icm42688p_read_gyro_raw(imu->icm42688p, &data);
        avg_x += data.x;
        avg_y += data.y;
        avg_z += data.z;
        furi_delay_ms(2);
    }

    data.x = avg_x / IMU_CALI_AVG;
    data.y = avg_y / IMU_CALI_AVG;
    data.z = avg_z / IMU_CALI_AVG;

    icm42688p_apply_scale(&data, icm42688p_gyro_get_full_scale(imu->icm42688p), &offset_scaled);
    FURI_LOG_I(
        TAG,
        "Offsets: x %f, y %f, z %f",
        (double)offset_scaled.x,
        (double)offset_scaled.y,
        (double)offset_scaled.z);
    icm42688p_write_gyro_offset(imu->icm42688p, &offset_scaled);
}

// static float imu_angle_diff(float a, float b) {
//     float diff = a - b;
//     if(diff > 180.f)
//         diff -= 360.f;
//     else if(diff < -180.f)
//         diff += 360.f;

//     return diff;
// }

static int32_t imu_thread(void* context) {
    furi_assert(context);
    ImuThread* imu = context;

    // float yaw_last = 0.f;
    // float pitch_last = 0.f;
    // float diff_x = 0.f;
    // float diff_y = 0.f;

    calibrate_gyro(imu);

    icm42688p_accel_config(imu->icm42688p, AccelFullScale16G, ACCEL_GYRO_RATE);
    icm42688p_gyro_config(imu->icm42688p, GyroFullScale2000DPS, ACCEL_GYRO_RATE);

    imu->processed_data.q0 = 1.f;
    imu->processed_data.q1 = 0.f;
    imu->processed_data.q2 = 0.f;
    imu->processed_data.q3 = 0.f;
    icm42688_fifo_enable(imu->icm42688p, imu_irq_callback, imu);

    while(1) {
        uint32_t events = furi_thread_flags_wait(FLAGS_ALL, FuriFlagWaitAny, FuriWaitForever);

        if(events & ImuStop) {
            break;
        }

        if(events & ImuNewData) {
            uint16_t data_pending = icm42688_fifo_get_count(imu->icm42688p);
            ICM42688PFifoPacket data;
            while(data_pending--) {
                icm42688_fifo_read(imu->icm42688p, &data);
                imu_process_data(imu, &data);
            }
        }
    }

    icm42688_fifo_disable(imu->icm42688p);

    return 0;
}

ImuThread* imu_start(ICM42688P* icm42688p) {
    ImuThread* imu = malloc(sizeof(ImuThread));
    imu->icm42688p = icm42688p;
    imu->thread = furi_thread_alloc_ex("ImuThread", 4096, imu_thread, imu);
    imu->lefty = furi_hal_rtc_is_flag_set(FuriHalRtcFlagHandOrient);
    furi_thread_start(imu->thread);

    return imu;
}

void imu_stop(ImuThread* imu) {
    furi_assert(imu);

    furi_thread_flags_set(furi_thread_get_id(imu->thread), ImuStop);

    furi_thread_join(imu->thread);
    furi_thread_free(imu->thread);

    free(imu);
}

static float imu_inv_sqrt(float number) {
    union {
        float f;
        uint32_t i;
    } conv = {.f = number};
    conv.i = 0x5F3759Df - (conv.i >> 1);
    conv.f *= 1.5f - (number * 0.5f * conv.f * conv.f);
    return conv.f;
}

/* Simple madgwik filter, based on: https://github.com/arduino-libraries/MadgwickAHRS/ */

static void imu_madgwick_filter(
    ImuProcessedData* out,
    ICM42688PScaledData* accel,
    ICM42688PScaledData* gyro) {
    float recipNorm;
    float s0, s1, s2, s3;
    float qDot1, qDot2, qDot3, qDot4;
    float _2q0, _2q1, _2q2, _2q3, _4q0, _4q1, _4q2, _8q1, _8q2, q0q0, q1q1, q2q2, q3q3;

    // Rate of change of quaternion from gyroscope
    qDot1 = 0.5f * (-out->q1 * gyro->x - out->q2 * gyro->y - out->q3 * gyro->z);
    qDot2 = 0.5f * (out->q0 * gyro->x + out->q2 * gyro->z - out->q3 * gyro->y);
    qDot3 = 0.5f * (out->q0 * gyro->y - out->q1 * gyro->z + out->q3 * gyro->x);
    qDot4 = 0.5f * (out->q0 * gyro->z + out->q1 * gyro->y - out->q2 * gyro->x);

    // Compute feedback only if accelerometer measurement valid (avoids NaN in accelerometer normalisation)
    if(!((accel->x == 0.0f) && (accel->y == 0.0f) && (accel->z == 0.0f))) {
        // Normalise accelerometer measurement
        recipNorm = imu_inv_sqrt(accel->x * accel->x + accel->y * accel->y + accel->z * accel->z);
        accel->x *= recipNorm;
        accel->y *= recipNorm;
        accel->z *= recipNorm;

        // Auxiliary variables to avoid repeated arithmetic
        _2q0 = 2.0f * out->q0;
        _2q1 = 2.0f * out->q1;
        _2q2 = 2.0f * out->q2;
        _2q3 = 2.0f * out->q3;
        _4q0 = 4.0f * out->q0;
        _4q1 = 4.0f * out->q1;
        _4q2 = 4.0f * out->q2;
        _8q1 = 8.0f * out->q1;
        _8q2 = 8.0f * out->q2;
        q0q0 = out->q0 * out->q0;
        q1q1 = out->q1 * out->q1;
        q2q2 = out->q2 * out->q2;
        q3q3 = out->q3 * out->q3;

        // Gradient decent algorithm corrective step
        s0 = _4q0 * q2q2 + _2q2 * accel->x + _4q0 * q1q1 - _2q1 * accel->y;
        s1 = _4q1 * q3q3 - _2q3 * accel->x + 4.0f * q0q0 * out->q1 - _2q0 * accel->y - _4q1 +
             _8q1 * q1q1 + _8q1 * q2q2 + _4q1 * accel->z;
        s2 = 4.0f * q0q0 * out->q2 + _2q0 * accel->x + _4q2 * q3q3 - _2q3 * accel->y - _4q2 +
             _8q2 * q1q1 + _8q2 * q2q2 + _4q2 * accel->z;
        s3 = 4.0f * q1q1 * out->q3 - _2q1 * accel->x + 4.0f * q2q2 * out->q3 - _2q2 * accel->y;
        recipNorm =
            imu_inv_sqrt(s0 * s0 + s1 * s1 + s2 * s2 + s3 * s3); // normalise step magnitude
        s0 *= recipNorm;
        s1 *= recipNorm;
        s2 *= recipNorm;
        s3 *= recipNorm;

        // Apply feedback step
        qDot1 -= FILTER_BETA * s0;
        qDot2 -= FILTER_BETA * s1;
        qDot3 -= FILTER_BETA * s2;
        qDot4 -= FILTER_BETA * s3;
    }

    // Integrate rate of change of quaternion to yield quaternion
    out->q0 += qDot1 * (1.0f / FILTER_SAMPLE_FREQ);
    out->q1 += qDot2 * (1.0f / FILTER_SAMPLE_FREQ);
    out->q2 += qDot3 * (1.0f / FILTER_SAMPLE_FREQ);
    out->q3 += qDot4 * (1.0f / FILTER_SAMPLE_FREQ);

    // Normalise quaternion
    recipNorm = imu_inv_sqrt(
        out->q0 * out->q0 + out->q1 * out->q1 + out->q2 * out->q2 + out->q3 * out->q3);
    out->q0 *= recipNorm;
    out->q1 *= recipNorm;
    out->q2 *= recipNorm;
    out->q3 *= recipNorm;
}

/* IMU API */

struct Imu {
    FuriHalSpiBusHandle* icm42688p_device;
    ICM42688P* icm42688p;
    ImuThread* thread;
    bool present;
};

Imu* imu_alloc(void) {
    Imu* imu = malloc(sizeof(Imu));
    imu->icm42688p_device = malloc(sizeof(FuriHalSpiBusHandle));
    memcpy(imu->icm42688p_device, &furi_hal_spi_bus_handle_external, sizeof(FuriHalSpiBusHandle));
    imu->icm42688p_device->cs = &gpio_ext_pc3;

    imu->icm42688p = icm42688p_alloc(imu->icm42688p_device, &gpio_ext_pb2);
    imu->present = icm42688p_init(imu->icm42688p);

    if(imu->present) {
        imu->thread = imu_start(imu->icm42688p);
    }

    return imu;
}

void imu_free(Imu* imu) {
    if(imu->present) {
        imu_stop(imu->thread);
    }
    icm42688p_deinit(imu->icm42688p);
    icm42688p_free(imu->icm42688p);
    free(imu->icm42688p_device);
    free(imu);
}

bool imu_present(Imu* imu) {
    return imu->present;
}

float imu_pitch_get(Imu* imu) {
    // we pretend that reading a float is an atomic operation
    return imu->thread->lefty ? -imu->thread->processed_data.pitch :
                                imu->thread->processed_data.pitch;
}

float imu_roll_get(Imu* imu) {
    // we pretend that reading a float is an atomic operation
    return imu->thread->processed_data.roll;
}

float imu_yaw_get(Imu* imu) {
    // we pretend that reading a float is an atomic operation
    return imu->thread->lefty ? -imu->thread->processed_data.yaw : imu->thread->processed_data.yaw;
}