core1.c

//////////////////////////
//   RP2040-Decoder     //
// Gabriel Koppenstein  //
//      core1.c         //
//////////////////////////

#include "core1.h"

struct repeating_timer pid_control_timer, speed_helper_timer;


// Get speed_step_table_index depending on speed_step
uint8_t get_speed_step_table_index_of_speed_step(uint8_t speed_step) {
    // Clear direction information in bit7
    speed_step = speed_step & 0b01111111;
    // Check for Stop or Emergency Stop speed step
    if (speed_step == 0 || speed_step == 1) {
        return 0;
    }
    // In any other case i.e. speed steps 1 to 126:
    return speed_step-1;
}


// This function gets called every x milliseconds where x is CV_175.
// The purpose of this function is to implement a time delay in acceleration or deceleration
bool speed_helper(struct repeating_timer *const t) {
    // pid->setpoint only gets adjusted when the speed_helper_counter is equal to the accel_rate/decel_rate
    // -> Time for 1 Speed Step := (speed_helper timer delay)*(accel_rate) or CV_175*CV_3 or CV_175*CV_4
    pid_params *const pid = (pid_params *) (t->user_data);
    const uint8_t accel_rate = CV_ARRAY_FLASH[2];
    const uint8_t decel_rate = CV_ARRAY_FLASH[3];
    static uint8_t speed_helper_counter;
    static uint8_t speed_table_index;

    // Get speed_step_table_end_index corresponding to current speed_step_target
    const uint8_t speed_step_table_end_index = get_speed_step_table_index_of_speed_step(speed_step_target);
    const bool direction_changed = get_direction_of_speed_step(speed_step_target) !=
                                   get_direction_of_speed_step(speed_step_target_prev);

    if (pid->speed_step_target == 129 || pid->speed_step_target == 1) {
        // Emergency Stop
        speed_table_index = 0;
        speed_helper_counter = 0;
        pid->setpoint = pid->speed_table[speed_table_index];
    }
    else if (speed_step_table_end_index > speed_table_index && speed_helper_counter == accel_rate) {
        // Acceleration
        if (!accel_rate) speed_table_index = speed_step_table_end_index; // directly accelerate to end target speed
        else speed_table_index++;
        pid->setpoint = pid->speed_table[speed_table_index];
        speed_helper_counter = 0;
    }
    else if (speed_step_table_end_index < speed_table_index && speed_helper_counter == decel_rate) {
        // Deceleration
        if (!decel_rate) speed_table_index = speed_step_table_end_index; // directly decelerate to end target speed
        else speed_table_index--;
        pid->setpoint = pid->speed_table[speed_table_index];
        speed_helper_counter = 0;
    }
    else if (direction_changed) {
        // Change of direction while decelerating -> jump to most recent speed_step without delay (other direction)
        speed_table_index = speed_step_table_end_index;
        pid->setpoint = pid->speed_table[speed_table_index];
        speed_helper_counter = 0;
    }
    else if (speed_step_table_end_index != speed_table_index) {
        // Acceleration/Deceleration "scheduled"
        speed_helper_counter++;
    }
    else {
        // Target reached -> Reset Counter
        speed_helper_counter = 0;
    }

    // return true to schedule the repeating timer again
    return true;
}


// Helper function to adjust pwm level/duty cycle.
void adjust_pwm_level(const uint16_t level) {
    if (get_direction_of_speed_step(speed_step_target)) {
        // Forward
        pwm_set_gpio_level(MOTOR_REV_PIN, 0);
        pwm_set_gpio_level(MOTOR_FWD_PIN, level);
    }
    else {
        // Reverse
        pwm_set_gpio_level(MOTOR_FWD_PIN, 0);
        pwm_set_gpio_level(MOTOR_REV_PIN, level);
    }
}


// Update feed-forward slope/gradient for both directions
void update_m(pid_params *const pid) {
    pid->m_fwd = (pid->y_2_fwd - pid->y_1_fwd) / (pid->x_2_fwd - pid->x_1_fwd);
    pid->m_rev = (pid->y_2_rev - pid->y_1_rev) / (pid->x_2_rev - pid->x_1_rev);
}


// Update feedforward function value y_2 in both directions
void update_y(pid_params *const pid, const float i) {
    if (get_direction_of_speed_step(speed_step_target)) {
        // Forward
        pid->y_2_fwd += i * pid->k_ff;
        // Limit y_2_fwd
        if (pid->y_2_fwd > pid->max_output) pid->y_2_fwd = pid->max_output;
        else if (pid->y_2_fwd < pid->y_1_fwd) pid->y_2_fwd = pid->y_1_fwd;
    }
    else {
        // Reverse
        pid->y_2_rev += i * pid->k_ff;
        // Limit y_2_rev
        if (pid->y_2_rev > pid->max_output) pid->y_2_rev = pid->max_output;
        else if (pid->y_2_rev < pid->y_1_rev) pid->y_2_rev = pid->y_1_rev;
    }
    update_m(pid);
}


// Returns feedforward value corresponding to current setpoint
float get_ff_val(const pid_params *const pid) {
    float val;
    if (get_direction_of_speed_step(speed_step_target)) {
        // Forward
        val = pid->m_fwd * ((float) pid->setpoint - pid->x_1_fwd) + pid->y_1_fwd;
    }
    else {
        // Reverse
        val = pid->m_rev * ((float) pid->setpoint - pid->x_1_rev) + pid->y_1_rev;
    }
    return val;
}


// Returns proportional gain value corresponding to current setpoint
float get_kp(const pid_params *const pid) {
    const float sp = (float) pid->setpoint;
    if (sp < pid->k_p_x_1) {
        return pid->k_p_m_1 * sp + pid->k_p_y_0;
    }
    return pid->k_p_m_2 * (sp - pid->k_p_x_1) + pid->k_p_y_1;
}


// PID controller function gets called every x milliseconds where x is CV_49 aka sampling time (pid->t)
bool pid_control(struct repeating_timer *const t) {
    // Cast (void *) to (pid_params *)
    pid_params *const pid = (pid_params *) (t->user_data);

    // Acceleration from standstill or change in direction -> reset previous derivative, error and integral parts
    const bool direction_changed = get_direction_of_speed_step(speed_step_target) !=
                                   get_direction_of_speed_step(speed_step_target_prev);
    if ((!pid->setpoint_prev && !pid->setpoint) || direction_changed) {
        pid->d_prev = 0.0f;
        pid->i_prev = 0.0f;
        pid->e_prev = 0.0f;
    }

    // Get feed-forward and proportional gain values
    const float feed_fwd = get_ff_val(pid);
    pid->k_p = get_kp(pid);

    // Measure BEMF voltage and compute error
    pid->measurement = measure(pid->msr_total_iterations,
                               pid->msr_delay_in_us,
                               pid->l_side_arr_cutoff,
                               pid->r_side_arr_cutoff,
                               get_direction_of_speed_step(speed_step_target));

    const float measurement_corrected = pid->measurement - pid->adc_offset;
    const float e = (float) pid->setpoint - measurement_corrected;

    // Proportional part, integral part and derivative part (including digital low-pass-filter with time constant tau)
    const float p = pid->k_p * e;
    float i = pid->ci_0 * (e + pid->e_prev) + pid->i_prev;
    const float d = pid->cd_0 * (pid->measurement - pid->measurement_prev) + pid->cd_1 * pid->d_prev;

    // Check for limits on the integral part
    if (i > pid->int_lim_max) {
        i = pid->int_lim_max;
    }
    else if (i < pid->int_lim_min) {
        i = pid->int_lim_min;
    }

    // Sum feed forward + all controller terms (p+i+d). Limit Output from 0% to 100% duty cycle
    float output = feed_fwd + p + i + d;
    if (output < 0 || !pid->setpoint) {
        output = 0.0f;
    }
    else if (output > pid->max_output) {
        output = pid->max_output;
    }

    if (LOGLEVEL >= 1) {
        static int counter = 0;
        counter++;
        if (counter > 100) {
            LOG(1, "pid error(%f) output(%f)\n", e, output);
            counter = 0;
        }
    }

    // Set PWM Level and discard results in adc fifo
    adjust_pwm_level((uint16_t) roundf(output));
    adc_fifo_drain();

    // Check for High or Low Integrator values -> Update x,y values of feedforward function
    if ((output < pid->max_output && output > pid->max_output / 2) &&
        ((i > pid->int_lim_max / 2) || (i < pid->int_lim_min / 2))) {
        update_y(pid, i);
    }

    // Save previous error, integrator, differentiator, direction, setpoint and measured value also sum error to e_sum
    pid->e_prev = e;
    pid->i_prev = i;
    pid->d_prev = d;
    pid->setpoint_prev = pid->setpoint;
    pid->measurement_prev = pid->measurement;

    // return true to schedule the repeating timer again
    return true;
}


// PID controller and measurement parameter, and speed_table initialization
void init_pid(pid_params *const pid) {
    // Measurement variables initialization
    pid->adc_offset = (float) CV_ARRAY_FLASH[171];
    pid->msr_total_iterations = CV_ARRAY_FLASH[60];
    pid->msr_delay_in_us = CV_ARRAY_FLASH[61];
    pid->l_side_arr_cutoff = CV_ARRAY_FLASH[62];
    pid->r_side_arr_cutoff = CV_ARRAY_FLASH[63];

    // Speed table initialization
    // Calculate speed setpoint table according to V_min, V_max and V_mid CVs
    const double v_min = (double) CV_ARRAY_FLASH[1];
    const double v_mid = (double) CV_ARRAY_FLASH[5] * 16;
    const double v_max = (double) CV_ARRAY_FLASH[4] * 16;

    LOG(1, "speedtable min(%f) mid(%f) max(%f)\n", v_min, v_mid, v_max);

    const double delta_x = 63;
    const double m_1 = (v_mid - v_min) / delta_x;
    const double m_2 = (v_max - v_mid) / delta_x;
    pid->speed_table[0] = 0;
    for (uint8_t i = 1; i < 64; ++i) {
        pid->speed_table[i] = (uint16_t) lround(m_1 * (i - 1) + v_min);
    }
    for (uint8_t i = 64; i < 127; ++i) {
        pid->speed_table[i] = (uint16_t) lround(m_2 * (i - 63) + v_mid);
    }

    // Controller constants initialization
    pid->k_i = (float) CV_ARRAY_FLASH[49] / 10;
    pid->k_d = (float) CV_ARRAY_FLASH[50] / 10000;
    pid->tau = (float) CV_ARRAY_FLASH[47] / 1000;
    pid->t = (float) CV_ARRAY_FLASH[48] / 1000;
    pid->ci_0 = (pid->k_i * pid->t) / 2;
    pid->cd_0 = -(2 * pid->k_d) / (2 * pid->tau + pid->t);
    pid->cd_1 = (2 * pid->tau - pid->t) / (2 * pid->tau + pid->t);
    pid->int_lim_max = 10 * (float) CV_ARRAY_FLASH[51];
    pid->int_lim_min = -10 * (float) CV_ARRAY_FLASH[52];
    pid->k_ff = (float) CV_ARRAY_FLASH[46] / 10000;
    pid->max_output = (float) (_125M / (CV_ARRAY_FLASH[8] * 100 + 10000));
    pid->x_1_rev = 0.0f;
    pid->x_1_fwd = 0.0f;
    pid->y_1_fwd = (float) get_16bit_CV(175);
    pid->y_1_rev = (float) get_16bit_CV(177);
    pid->x_2_rev = (float) pid->speed_table[126];
    pid->x_2_fwd = (float) pid->speed_table[126];

    // Controller variables initialization
    pid->y_2_fwd = pid->max_output;
    pid->y_2_rev = pid->max_output;
    pid->measurement = 0.0f;
    pid->measurement_prev = 0.0f;
    pid->e_prev = 0.0f;
    pid->i_prev = 0.0f;
    pid->d_prev = 0.0f;
    pid->setpoint = 0;

    // Gain scheduling initialization
    pid->k_p_x_1_shift = (float) CV_ARRAY_FLASH[59] / 255.0f;
    pid->k_p_x_1 = (float) pid->speed_table[126] * pid->k_p_x_1_shift;
    pid->k_p_x_2 = (float) pid->speed_table[126] * (1.0f - pid->k_p_x_1_shift);
    pid->k_p_y_0 = (float) get_16bit_CV(53) / 100.0f;
    pid->k_p_y_1 = (float) get_16bit_CV(55) / 100.0f;
    pid->k_p_y_2 = (float) get_16bit_CV(57) / 100.0f;
    pid->k_p_m_1 = (pid->k_p_y_1 - pid->k_p_y_0) / pid->k_p_x_1;
    pid->k_p_m_2 = (pid->k_p_y_2 - pid->k_p_y_1) / pid->k_p_x_2;

    update_m(pid);
}

void core1_entry() {
    LOG(1, "core1 init...\n");
    pid_params pid_parameters;
    pid_params *pid = &pid_parameters;
    init_pid(pid);
    alarm_pool_add_repeating_timer_ms(alarm_pool_create(0, 1),
                                      CV_ARRAY_FLASH[48],
                                      pid_control,
                                      pid,
                                      &pid_control_timer);
    // Set TIMER_IRQ_0 to highest priority of 0x00
    irq_set_priority(TIMER_IRQ_0, 0x00);
    alarm_pool_add_repeating_timer_ms(alarm_pool_create(1, 1),
                                      CV_ARRAY_FLASH[174],
                                      speed_helper,
                                      pid,
                                      &speed_helper_timer);
    LOG(1, "core1 done\n");
    while (true);
}