스테퍼 모터 제어 — Full Step·Half Step·Microstepping

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// STEP = PA0, DIR = PA1, /EN = PA2
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void stepper_init(void) {
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    RCC->AHB1ENR |= RCC_AHB1ENR_GPIOAEN;
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    gpio_init(GPIOA, 0, &(gpio_config_t){.mode=GPIO_MODE_OUTPUT, .speed=GPIO_SPEED_HIGH});
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    gpio_init(GPIOA, 1, &(gpio_config_t){.mode=GPIO_MODE_OUTPUT});
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    gpio_init(GPIOA, 2, &(gpio_config_t){.mode=GPIO_MODE_OUTPUT});
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    GPIOA->BSRR = (1u << (2 + 16));   // EN low = enable
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}
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void stepper_step(int dir) {
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    if (dir > 0) GPIOA->BSRR = (1u << (1 + 16));   // DIR=0
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    else         GPIOA->BSRR = (1u << 1);          // DIR=1
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    GPIOA->BSRR = (1u << 0);          // STEP high
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    delay_us(2);                       // DRV8825 minimum 1.9 µs
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    GPIOA->BSRR = (1u << (0 + 16));   // STEP low
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    delay_us(2);
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}
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// 1초에 1 회전 (200 step → 5 ms/step)
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for (int i = 0; i < 200; i++) {
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    stepper_step(1);
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    delay_us(5000 - 4);
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}

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volatile int32_t target_steps;
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volatile int32_t current_steps;
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volatile int8_t  step_dir;
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void stepper_tim_init(uint32_t step_hz) {
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    RCC->APB1ENR |= RCC_APB1ENR_TIM3EN;
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    TIM3->PSC = 84 - 1;                // 84 MHz / 84 = 1 MHz tick
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    TIM3->ARR = (1000000u / step_hz) - 1;
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    TIM3->DIER = TIM_DIER_UIE;
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    TIM3->CR1 = TIM_CR1_CEN;
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    NVIC_EnableIRQ(TIM3_IRQn);
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}
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void stepper_move(int32_t steps) {
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    if (steps > 0) { step_dir = +1; GPIOA->BSRR = (1u << (1+16)); }
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    else           { step_dir = -1; GPIOA->BSRR = (1u << 1); }
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    target_steps = current_steps + steps;
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}
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void TIM3_IRQHandler(void) {
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    TIM3->SR &= ~TIM_SR_UIF;
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    if (current_steps != target_steps) {
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        GPIOA->BSRR = (1u << 0);
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        // 약간의 delay 후 low (간단히 다음 IRQ 사이에 low되도록)
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        for (volatile int i = 0; i < 5; i++);
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        GPIOA->BSRR = (1u << (0+16));
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        current_steps += step_dir;
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    }
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}

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typedef struct {
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    int32_t target;
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    int32_t current;
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    int32_t accel;     // step/s²
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    int32_t max_vel;   // step/s
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    int32_t velocity;  // current
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    uint32_t last_step_us;
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} stepper_t;
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uint32_t stepper_next_delay_us(stepper_t *s) {
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    int32_t remaining = abs(s->target - s->current);
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    // Decelerate if needed: v² = 2 a d
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    int32_t decel_dist = (s->velocity * s->velocity) / (2 * s->accel);
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    if (remaining <= decel_dist) {
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        s->velocity = (int32_t)sqrtf(2.0f * s->accel * remaining);
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    } else if (s->velocity < s->max_vel) {
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        // Accelerate
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        s->velocity += s->accel / 1000;   // small step
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        if (s->velocity > s->max_vel) s->velocity = s->max_vel;
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    }
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    if (s->velocity < 100) s->velocity = 100;   // min
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    return 1000000u / s->velocity;
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}

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void stepper_set_microstep(uint8_t div) {
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    // div: 1, 2, 4, 8, 16, 32
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    // MS1, MS2, MS3 (DRV8825)
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    uint8_t ms = 0;
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    switch (div) {
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        case 1:  ms = 0b000; break;
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        case 2:  ms = 0b001; break;
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        case 4:  ms = 0b010; break;
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        case 8:  ms = 0b011; break;
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        case 16: ms = 0b100; break;
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        case 32: ms = 0b111; break;
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    }
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    GPIOB->BSRR = (ms & 1)      ? (1u << 0)  : (1u << 16);
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    GPIOB->BSRR = (ms & 2)      ? (1u << 1)  : (1u << 17);
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    GPIOB->BSRR = (ms & 4)      ? (1u << 2)  : (1u << 18);
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}