'''
实验：超声波测距
接线：TRIG→GP14, ECHO→GP13
'''
from machine import Pin
import utime

trigger = Pin(14, Pin.OUT)
echo = Pin(13, Pin.IN)

def get_distance():
    """测量距离（厘米）"""
    # 发送触发脉冲
    trigger.low()
    utime.sleep_us(2)
    trigger.high()
    utime.sleep_us(10)
    trigger.low()
    
    # 等待回波开始
    while echo.value() == 0:
        start = utime.ticks_us()
    
    # 等待回波结束
    while echo.value() == 1:
        end = utime.ticks_us()
    
    # 计算距离
    duration = utime.ticks_diff(end, start)
    # 声速 343.2 m/s = 0.0343 cm/μs
    distance = duration * 0.0343 / 2
    
    return distance

while True:
    dist = get_distance()
    print(f"距离: {dist:.2f} cm")
    utime.sleep(0.5)

'''
实验：带超时保护的测距
'''
def get_distance_safe(timeout_us=30000):
    """带超时的测距"""
    trigger.low()
    utime.sleep_us(2)
    trigger.high()
    utime.sleep_us(10)
    trigger.low()
    
    # 等待回波开始（带超时）
    start_wait = utime.ticks_us()
    while echo.value() == 0:
        if utime.ticks_diff(utime.ticks_us(), start_wait) > timeout_us:
            return -1  # 超时
    start = utime.ticks_us()
    
    # 等待回波结束（带超时）
    while echo.value() == 1:
        if utime.ticks_diff(utime.ticks_us(), start) > timeout_us:
            return -2  # 超出量程
    end = utime.ticks_us()
    
    duration = utime.ticks_diff(end, start)
    distance = duration * 0.0343 / 2
    
    return distance

while True:
    dist = get_distance_safe()
    
    if dist == -1:
        print("超时：无回波")
    elif dist == -2:
        print("超出量程")
    else:
        print(f"距离: {dist:.2f} cm")
    
    utime.sleep(0.5)

'''
实验：中值滤波测距
'''
def get_distance_filtered(samples=5):
    """中值滤波"""
    readings = []
    
    for _ in range(samples):
        d = get_distance_safe()
        if d > 0:
            readings.append(d)
        utime.sleep_ms(60)  # 采样间隔
    
    if not readings:
        return -1
    
    readings.sort()
    return readings[len(readings) // 2]

while True:
    dist = get_distance_filtered(5)
    
    if dist > 0:
        print(f"距离: {dist:.2f} cm")
    else:
        print("测量失败")
    
    utime.sleep(0.5)

'''
实验：距离 LED 条显示
'''
from machine import Pin
import neopixel

np = neopixel.NeoPixel(Pin(16), 8)

def distance_to_leds(dist):
    """距离映射到 LED"""
    max_dist = 100  # 最大显示距离 (cm)
    
    if dist < 0:
        # 错误状态 - 全红闪烁
        np.fill((255, 0, 0))
    else:
        # 距离越近，亮的 LED 越多
        lit = int((1 - min(dist, max_dist) / max_dist) * 8)
        
        for i in range(8):
            if i < lit:
                if lit > 6:
                    np[i] = (255, 0, 0)    # 危险 - 红
                elif lit > 4:
                    np[i] = (255, 255, 0)  # 警告 - 黄
                else:
                    np[i] = (0, 255, 0)    # 安全 - 绿
            else:
                np[i] = (0, 0, 0)
    
    np.write()

while True:
    dist = get_distance_filtered()
    distance_to_leds(dist)
    print(f"距离: {dist:.1f} cm")
    utime.sleep(0.1)

'''
实验：倒车雷达（蜂鸣器频率变化）
'''
from machine import Pin, PWM

buzzer = PWM(Pin(21))

def distance_to_beep(dist):
    """距离映射到蜂鸣频率"""
    if dist < 0 or dist > 200:
        buzzer.duty_u16(0)
        return
    
    if dist < 10:
        # 很近 - 持续响
        buzzer.freq(2000)
        buzzer.duty_u16(5000)
    elif dist < 30:
        # 近 - 快速间歇
        buzzer.freq(1500)
        buzzer.duty_u16(3000)
        utime.sleep_ms(50)
        buzzer.duty_u16(0)
        utime.sleep_ms(50)
    elif dist < 60:
        # 中等 - 慢速间歇
        buzzer.freq(1000)
        buzzer.duty_u16(2000)
        utime.sleep_ms(100)
        buzzer.duty_u16(0)
        utime.sleep_ms(200)
    else:
        # 远 - 不响
        buzzer.duty_u16(0)

while True:
    dist = get_distance_safe()
    distance_to_beep(dist)

'''
实验：水箱液位监测
'''
TANK_HEIGHT = 100  # 水箱高度 (cm)
SENSOR_OFFSET = 5  # 传感器距顶部距离 (cm)

def get_water_level():
    """获取水位百分比"""
    dist = get_distance_filtered()
    
    if dist < 0:
        return -1
    
    # 水位 = 总高度 - 空气层高度
    water_height = TANK_HEIGHT - (dist - SENSOR_OFFSET)
    water_percent = max(0, min(100, water_height / TANK_HEIGHT * 100))
    
    return water_percent

while True:
    level = get_water_level()
    
    if level >= 0:
        bar = '█' * int(level / 5)
        print(f"水位: {level:.1f}% |{bar}|")
    else:
        print("测量错误")
    
    utime.sleep(1)

'''
实验：智能垃圾桶（自动开盖）
'''
from machine import PWM

servo = PWM(Pin(16))
servo.freq(50)

def set_lid(open_state):
    """控制垃圾桶盖"""
    if open_state:
        duty = 8192   # 开盖 (约 180°)
    else:
        duty = 1638   # 关盖 (约 0°)
    servo.duty_u16(duty)

lid_open = False
close_timer = 0

while True:
    dist = get_distance_safe()
    
    if 5 < dist < 30:  # 检测到靠近
        if not lid_open:
            set_lid(True)
            lid_open = True
            print("开盖")
        close_timer = utime.ticks_ms()
    else:
        # 3 秒无人后关盖
        if lid_open and utime.ticks_diff(utime.ticks_ms(), close_timer) > 3000:
            set_lid(False)
            lid_open = False
            print("关盖")
    
    utime.sleep_ms(100)

'''
实验：温度补偿测距
'''
def get_distance_compensated(temperature=25):
    """温度补偿的距离测量"""
    # 计算声速 (cm/μs)
    speed_of_sound = (331.3 + 0.606 * temperature) / 10000
    
    trigger.low()
    utime.sleep_us(2)
    trigger.high()
    utime.sleep_us(10)
    trigger.low()
    
    while echo.value() == 0:
        start = utime.ticks_us()
    
    while echo.value() == 1:
        end = utime.ticks_us()
    
    duration = utime.ticks_diff(end, start)
    distance = duration * speed_of_sound / 2
    
    return distance

# 假设温度 30°C
dist_25 = get_distance_safe()
dist_30 = get_distance_compensated(30)

print(f"25°C 默认: {dist_25:.2f} cm")
print(f"30°C 补偿: {dist_30:.2f} cm")