foc/3rd/lowpass_filter.c

#include <stdint.h>
#include <ti_msp_dl_config.h>

float y = 0;
float Lowpassfilter_sim(float x)
{
    float out = 0.9 * x + 0.1 * y;
    y = x;
    return out;
}

uint32_t Last_Timesamp = 0.0;
float Last_y = 0.0;
float Lowpassfilter(float Tf, float x)
{
    float dt = 0.0;

    uint32_t Timesamp = DL_SYSTICK_getValue();
    if(Timesamp < Last_Timesamp)
    {
        dt = (float)(Last_Timesamp - Timesamp) / 80 * 1e-6;
    }
    else
    {
        dt = (float)(0xFFFFFF - Timesamp + Last_Timesamp) / 80 * 1e-6;
    }

    if(dt < 0.0 || dt == 0)
    {
        dt = 0.0015f;
    }
    else if(dt > 0.005f)
    {
        Last_y = x;
        Last_Timesamp = Timesamp;
        return x;
    }
    float alpha = Tf / (Tf + dt);
    float y = alpha * Last_y + (1.0f - alpha) * x;

    Last_y = y;
    Last_Timesamp = Timesamp;


    return y;
}