限制

初始化限制类

使用以下构造函数创建限位开关：

Limit(port)

此构造函数使用一个参数：

范围	描述
port	The 3-Wire Port that the Limit Switch is connected to, whether it’s a port on the Brain, or a 3-Wire Expander.

A Brain or 3-Wire Expander must be created first before they can be used to create an object with the Limit Class constructor.

# Create the Brain.
brain = Brain()
# Construct a Limit Switch "limit" with the Limit class.
limit = Limit(brain.three_wire_port.a)

This limit object will be used in all subsequent examples throughout this API documentation when referring to Limit class methods.

类方法

pressed()

The pressed(callback, arg) method registers a callback function for when the Limit Switch is pressed.

参数	描述
callback	按下限位开关时调用的回调函数。
arg	**可选。**传递给回调函数的参数元组。

**返回：**无。

# Define a function switch_pressed().
def switch_pressed():
    # The Brain will print that the Limit Switch was pressed 
    # on the Brain's screen.
    brain.screen.print("switch pressed")
# Run switch_pressed when the Limit Switch is pressed.
limit.pressed(switch_pressed)

released()

The released(callback, arg) method registers a callback function for when the Limit Switch is released.

参数	描述
callback	当限位开关被释放时调用的回调函数。
arg	**可选。**传递给回调函数的参数元组。

**返回：**无。

# Define a function switch_released().
def switch_released():
    # The Brain will print that the Limit Switch was released
    # on the Brain's screen.
    brain.screen.print("switch released") 
# Run switch_released when the Limit Switch is released.
limit.released(switch_released)

pressing()

The pressing() method checks if the Limit Switch is currently being pressed.

Returns: True if the Limit Switch is currently being pressed. False if it is not.