3. grayscale.py Module

Similarly, in order to keep the code simple and organized when using the grayscale module with other modules, we have encapsulated all its related code into a library.

When you use it, you just need to import this library, and you can call the functions inside directly.

For example, the following two functions can be used to know if a cliff or black line is detected.

is_on_edge()
get_line_status()

Note

The final encapsulated library grayscale.py has been saved in pico_4wd_car-v2.0\libs, which may differ from the ones shown in the course, so please refer to the file under libs path when using it.

1. Create Grayscale class

Encapsulate the code related to the grayscale module into a library, as follows.

from machine import Pin, ADC

class Grayscale():

    def __init__(self, pin0=26, pin1=27, pin2=28):
        self.gs0 = ADC(Pin(pin0))
        self.gs1 = ADC(Pin(pin1))
        self.gs2 = ADC(Pin(pin2))
        self.edge_ref = 1000    # edge_reference
        self.line_ref = 10000 # line_reference

    def get_value(self):
        return [self.gs0.read_u16(), self.gs1.read_u16(), self.gs2.read_u16()]

    def is_on_edge(self):
        gs_list = self.get_value()
        return gs_list[2] <= self.edge_ref or gs_list[1] <= self.edge_ref or gs_list[0] <= self.edge_ref

    def get_line_status(self):
        gs_list = self.get_value()
        return [int(value < self.line_ref) for value in gs_list]

# init
gs = Grayscale(26, 27, 28)

# detect
while True:
    if gs.is_on_edge():
        print("Danger!")
    else:
        print(gs.get_line_status())

2. Add threshold changeable function

We have written cliff and black line thresholds in this module(library), but the thresholds are different for different environments when using it. So 2 other functions were created to make it easy for you to modify the thresholds in the main program.

from machine import Pin, ADC

class Grayscale():

    def __init__(self, pin0=26, pin1=27, pin2=28):
        self.gs0 = ADC(Pin(pin0))
        self.gs1 = ADC(Pin(pin1))
        self.gs2 = ADC(Pin(pin2))
        self.edge_ref = 1000    # edge_reference
        self.line_ref = 10000 # line_reference

    def get_value(self):
        return [self.gs0.read_u16(), self.gs1.read_u16(), self.gs2.read_u16()]

    def is_on_edge(self):
        gs_list = self.get_value()
        return gs_list[2] <= self.edge_ref or gs_list[1] <= self.edge_ref or gs_list[0] <= self.edge_ref

    def get_line_status(self):
        gs_list = self.get_value()
        return [int(value < self.line_ref) for value in gs_list]

    def set_edge_reference(self, value):
        self.edge_ref = value

    def set_line_reference(self, value):
        self.line_ref = value

if __name__ == '__main__':
    import time

    # init
    gs = Grayscale(26, 27, 28)

    # config
    gs.set_edge_reference(800)
    gs.set_line_reference(12000)

    # detect
    while True:
        if gs.is_on_edge():
            print("Danger!")
        else:
            print(gs.get_line_status())
        time.sleep(0.2)