Data transfer between APP and Pico

From APP to Pico-4wd

Let’s take a look at what kind of data Pico-4wd will get from the APP. Print data directly in on_receive.

Note

• Open the app_test.py file under the path of pico_4wd_car\tests or copy this code into Thonny.

• Rewrite the on_receive(data) function to only print data as shown below.

• Then click “Run Current Script” or simply press F5 to run it.

• Don’t forget to click on the “MicroPython (Raspberry Pi Pico)” interpreter in the bottom right corner.

• Each time you rerun the code, you need to connect your device’s Wi-Fi to my_4wd_car , then turn on SunFounder Controller and reconnect.

from ws import WS_Server
import json
import time
import pico_4wd as car

NAME = 'my_4wd_car'

## Client Mode
# WIFI_MODE = "sta"
# SSID = "YOUR SSID HERE"
# PASSWORD = "YOUR PASSWORD HERE"

## AP Mode
WIFI_MODE = "ap"
SSID = ""
PASSWORD = "12345678"

ws = WS_Server(name=NAME, mode=WIFI_MODE, ssid=SSID, password=PASSWORD)
ws.start()

def on_receive(data):
    # write control codes here.
    print(data)

    # write sensor codes here.
    pass

ws.on_receive = on_receive

def main():
    print("start")
    while True:
        ws.loop()

try:
    main()
finally:
    car.move("stop")
    car.set_light_off()

You will be able to see the following string:

{'J': None, 'A': None, 'L': None, 'K': None, 'F': None, 'M': None, 'H': 50, 'Q': None, 'G': None, 'I': None, 'B': None, 'D': None, 'C': None, 'N': None, 'E': None, 'P': None, 'O': None}

As we can see, the value of H Box is 50 ('H': 50), and the others are None. This is because we only add one control widget (H Box), and the slide widget was dragged to the 50 position. The widget in the D area is not used for control but only for show.

We can also add other control widgets, and use the same method to view the values ​​sent by these widgets to Pico-4wd.

You can get the value of the corresponding widget by just using the label. Let’s rewrite on_receive(data) again. As shown below, print the value of the H Box widget:

def on_receive(data):
    # write control codes here.
    print(data['H'])

    # write sensor codes here.
    pass

>>> %Run -c $EDITOR_CONTENT
    Connecting
    WebServer started on ws://192.168.4.1:8765
    start
    Connected from 192.168.4.3
    50
    50
    50

The values obtained from the app can be used to control the car. Rewrite on_receive(data) once again. As shown below, use the obtained H Box widget (Slider) value to control the RGB Board at the rear of the car.

def on_receive(data):
    # write control codes here.
    num = int(data['H']*9/100)
    for i in range(0,num):
        car.write_light_color_at(i, [80, 50, 0])
    for i in range(num,8):
        car.write_light_color_at(i, [0, 0, 0])
    car.light_excute()

You can use API file to help you understand the functions in the code.

From Pico-4wd to APP

Now let’s see what kind of data Pico-4wd will send to the APP. Rewrite on_receive(data) as shown below. The following code is used to obtain the ultrasonic detection distance.

from ws import WS_Server
import json
import time
import pico_4wd as car

NAME = 'my_4wd_car'

## Client Mode
# WIFI_MODE = "sta"
# SSID = "YOUR SSID HERE"
# PASSWORD = "YOUR PASSWORD HERE"

## AP Mode
WIFI_MODE = "ap"
SSID = ""
PASSWORD = "12345678"

ws = WS_Server(name=NAME, mode=WIFI_MODE, ssid=SSID, password=PASSWORD)
ws.start()

def on_receive(data):
    # write sensor codes here.
    data = car.get_radar_distance()
    print(data)

ws.on_receive = on_receive

def main():
    print("start")
    while True:
        ws.loop()

try:
    main()
finally:
    car.move("stop")
    car.set_light_off()

>>> %Run -c $EDITOR_CONTENT
    Connecting
    WebServer started on ws://192.168.4.1:8765
    start
    Connected from 192.168.4.2
    [-10, 49.249]
    [-20, 37.417]
    [-30, 38.947]
    [-40, 36.193]
    [-50, 40.12]
    [-60, 36.431]

You can use API file to help you understand the functions in the code.

Now, Rewrite on_receive(data), use the send_dict function to show the distance value in D Widget.

def on_receive(data):
    # write sensor codes here.
    data = car.get_radar_distance()
    print(data)
    ws.send_dict['D'] = data