Hardware Configuration

Motor Driver Connection

Connect the development board to the stepper motor driver using the following GPIO pin assignments:

• GPIO PC5 -> Driver IN1
• GPIO PC6 -> Driver IN2
• GPIO PC8 -> Driver IN3
• GPIO PC9 -> Driver IN4

Ensure proper 5V and GND connections are established between the boards.

Stepper Motor Excitation Methods

Single-Phase Excitation (4-Phase, 4-Step)

Activates one coil at a time in sequence.

• Advantages: Simple implementation, low power consumption
• Disadvantages: Lower torque, increased vibration

Sequence: A → B → C → D GPIO pattern: IN1 high → IN2 high → IN3 high → IN4 high

Dual-Phase Excitation (4-Phase, 4-Step)

Activates two coils simultaneous during each step.

• Advantages: Higher torque, reduced vibration
• Disadvantages: Standard step angle resolution

Sequence: AB → BC → CD → DA GPIO pattern: IN1+IN2 high → IN2+IN3 high → IN3+IN4 high → IN4+IN1 high

Hybrid Excitation (4-Phase, 8-Step)

Alternates between single and dual-phase activation for half-step operation.

• Advantages: Higher precision, smoother operation

Sequence: A → AB → B → BC → C → CD → D → DA

Binary Phase Representation

Counter-Clockwise Rotation

uint8_t phase_CCW[8] = {0x08, 0x0C, 0x04, 0x06, 0x02, 0x03, 0x01, 0x09};
Binary: 1000, 1100, 0100, 0110, 0010, 0011, 0001, 1001

Clockwise Rotation

uint8_t phase_CW[8] = {0x09, 0x01, 0x03, 0x02, 0x06, 0x04, 0x0C, 0x08};
Binary: 1001, 0001, 0011, 0010, 0110, 0100, 1100, 1000

Device Tree Configuration

Add the following configuration to board.dts, ensuring GPIO conflicts are resolved:

focus_motor: focus_motor {
    compatible = "motor-control";
    phase-count = <4>;
    phase0-gpio = <&pio PC 5 GPIO_ACTIVE_HIGH>;
    phase1-gpio = <&pio PC 6 GPIO_ACTIVE_HIGH>;
    phase2-gpio = <&pio PC 8 GPIO_ACTIVE_HIGH>;
    phase3-gpio = <&pio PC 9 GPIO_ACTIVE_HIGH>;
    step-resolution = <8>;
    clockwise-sequence = /bits/ 8 <0x09 0x01 0x03 0x02 0x06 0x04 0x0c 0x08>;
    counterclockwise-sequence = /bits/ 8 <0x08 0x0c 0x04 0x06 0x02 0x03 0x01 0x09>;
    phase-delay-us = <5>;
    step-delay-ms = <2>;
    status = "okay";
};

Driver Implementation

Phase Control Function

static void apply_motor_phase(struct device *dev, int *gpio_pins, 
                             int pin_count, uint8_t phase_pattern, int delay_us)
{
    int pin_state;
    
    for (int i = 0; i < pin_count; i++) {
        pin_state = (phase_pattern >> i) & 0x01;
        gpio_set_value(gpio_pins[i], pin_state);
        udelay(delay_us);
    }
}

Motor Stop Function

static void halt_motor(struct device *dev, int *gpio_pins, int pin_count)
{
    for (int i = 0; i < pin_count; i++) {
        gpio_set_value(gpio_pins[i], 0);
    }
}

Step Execution Logic

static int execute_motor_steps(struct motor_driver *driver, struct movement_data *params)
{
    uint8_t *phase_sequence;
    
    switch (params->direction) {
    case CLOCKWISE:
        phase_sequence = driver->cw_sequence;
        break;
    case COUNTERCLOCKWISE:
        phase_sequence = driver->ccw_sequence;
        break;
    default:
        return -EINVAL;
    }
    
    for (int cycle = 0; cycle < params->step_count; cycle++) {
        for (int phase = 0; phase < driver->step_resolution; phase++) {
            apply_motor_phase(driver->dev, driver->phase_pins, 
                            driver->phase_count, phase_sequence[phase], 
                            driver->phase_delay);
            mdelay(driver->step_delay);
        }
    }
    
    halt_motor(driver->dev, driver->phase_pins, driver->phase_count);
    return 0;
}

System Verification

Driver Initialization Check

Verify driver loading with dmesg:

dmesg | grep motor-control

Expected output includes phase configuration parameters and successful probe status.

Motor Control Testing

Execute clockwise rotation (100 steps):

echo 1,100 > /sys/devices/platform/focus_motor/motor_ctrl

Execute counterclockwise rotation (100 steps):

echo 2,100 > /sys/devices/platform/focus_motor/motor_ctrl