Openmv recognizes TWO-DIMENSIONAL code, color recognition and serial port communication
Objective Two-dimensional code recognition color recognition serial port communication complete code

purpose
1. Specify the content of the QR code: “XXX + XXX”, identify, return and send the corresponding serial number to the serial port; 2. Identify the color of materials in order according to the content of the two-dimensional code
3. Turn on the green light when standby, turn on the blue light when performing the action, and turn off the LED when the action is over.
Two-dimensional code recognition

while(True):
    img = sensor.snapshot()
    img.lens_corr(1.8)
    for code in img.find_qrcodes():
        output_str="%s" % code.payload()
		#output_str is QR code content

Attached (Forage TWO-DIMENSIONAL code generator)
Color identification

#Color Threshold
green_threshold   = (73, 96, -79, -22, -128, 127)
red_threshold   = (41, 61, 42, 127, -128, 127)
blue_threshold   = (22, 67, 9, 127, -128, -54)

blobs = img.find_blobs([green_threshold,red_threshold,blue_threshold],x_stride=25,y_stride=50,area_threshold=1000)
for b in blobs:
	img.draw_rectangle(b[0:4]) # rect
    #Mark the target color area with a rectangle
    img.draw_cross(b[5], b[6]) # cx, cy
    # draw a cross in the center of the target color area
    print(b[8]) # b[8] is the color code, red=2,green=1,blue=4

A serial port communication

if uart.any():# determine if data is received
	getrx = uart.readline()# read data
	uart.write('abc')#Send data

The complete code

import sensor, image, time, pyb
import ujson
from pyb import UART

green_threshold   = (73, 96, -79, -22, -128, 127)
#(0, 100, -128, -25, -128, 127)
red_threshold   = (41, 61, 42, 127, -128, 127)
#(41, 61, 42, 127, -128, 127)
blue_threshold   = (22, 67, 9, 127, -128, -54)
#(15, 100, -128, 127, -128, -41)
#red=2,green=1,blue=4
getrx = 0
getcmd = 0
renum = 0
colornum = 0
ptrposition = 0
sensor.reset()# Initialize the camera
sensor.set_pixformat(sensor.RGB565)# formatted as RGB565.
sensor.set_framesize(sensor.QQVGA) # Use QQVGA for faster speed
sensor.skip_frames(time = 2000) # Skip 2000s, make the new settings take effect, and adjust the white balance automatically
sensor.set_auto_gain(False) # Turn off auto gain. The default is on, in the color recognition, make sure to turn off the white balance.
sensor.set_auto_whitebal(False)
# Turn off white balance. White balance is on by default. In color recognition, be sure to turn off white balance.
clock = time.clock() # Track frame rate
led = pyb.LED(1) # Red LED = 1, Green LED = 1, Blue LED = 2, IR LEDs = 4.
uart = UART(3, 115200, timeout_char = 1000)
led.on()

def Rec_NUM1(lista):
    if (lista[0]=='1' and lista[1]=='2' and lista[2]=='3'):
        return 1
    elif (lista[0]=='1' and lista[1]=='3' and lista[2]=='2'):
        return 2
    elif (lista[0]=='2' and lista[1]=='1' and lista[2]=='3'):
        return 3
    elif (lista[0]=='2' and lista[1]=='3' and lista[2]=='1'):
        return 4
    elif (lista[0]=='3' and lista[1]=='1' and lista[2]=='2'):
        return 5
    elif (lista[0]=='3' and lista[1]=='2' and lista[2]=='1'):
        return 6

def Rec_NUM2(lista):
    if (lista[4]=='1' and lista[5]=='2' and lista[6]=='3'):
        return 1
    elif (lista[4]=='1' and lista[5]=='3' and lista[6]=='2'):
        return 2
    elif (lista[4]=='2' and lista[5]=='1' and lista[6]=='3'):
        return 3
    elif (lista[4]=='2' and lista[5]=='3' and lista[6]=='1'):
        return 4
    elif (lista[4]=='3' and lista[5]=='1' and lista[6]=='2'):
        return 5
    elif (lista[4]=='3' and lista[5]=='2' and lista[6]=='1'):
        return 6

while(True):
    clock.tick() # Track elapsed milliseconds between snapshots().
    if uart.any():
        led.off()
        getrx = uart.readline()
        time.sleep(150)     #Time delay 150ms
        led = pyb.LED(2)
        led.on()
        getcmd = int(getrx)
        print(getcmd)
      #  print(img.find_qrcodes())
    img = sensor.snapshot()# 从The light-sensitive chip acquires an image
    img.lens_corr(1.8) # strength of 1.8 is good for the 2.8mm lens.
    blobs = img.find_blobs([green_threshold,red_threshold,blue_threshold],x_stride=25,y_stride=50,area_threshold=1000)
    if(getcmd==2):
        for code in img.find_qrcodes():
            output_str="%s" % code.payload() #Method 1
            renum = int(Rec_NUM1(output_str)*10 + Rec_NUM2(output_str))
            uart.write(ujson.dumps(renum))
            getcmd = 0
            led.off()
    if blobs and getcmd==3:
        for b in blobs:
            # Draw a rect around the blob.
            img.draw_rectangle(b[0:4]) # rect
            #Mark the target color area with a rectangle
            img.draw_cross(b[5], b[6]) # cx, cy
            # Draw a cross in the center of the target color area
            #print(b[5], b[6], b[8])
            #uart.write(ujson.dumps(b[8]))
            #transfer color serial number to race serial number
            if b[8]==1:
                colornum=2
            elif b[8]==2:
                colornum=1
            elif b[8]==4:
                colornum=3
            print('colornum=',colornum,'output_str[ptrposition]=',output_str[ptrposition])
            #If the task code corresponds to
            if (int(output_str[ptrposition]) == colornum):
                uart.write('t')
                ptrposition+=1
                if ptrposition==4:
                    ptrposition+=1
                getcmd=0

For.html projects, add placeholder.js after introducing jquery to the page you need
Since I’m a vue+elementUI project, I don’t refresh the browser every time I switch menus, so I’ve cleaned up the usage in vUE
Jquery file also needs to be introduced here, otherwise the error may be reported. Just introduce jquery in index.html

Here’s how to use it in a Vue
First create placeholder.js file in the public JS file and output a PlaceholderInit function

//Solve the problem that the placeholder of input is not displayed under ie.

export function PlaceholderInit() {
  return jQuery(function() {
    var placeholderfriend = {
      focus: function(s) {
        s = $(s)
          .hide()
          .prev()
          .show()
          .focus();
        var idValue = s.attr("id");
        if (idValue) {
          s.attr("id", idValue.replace("placeholderfriend", ""));
        }
        var clsValue = s.attr("class");
        if (clsValue) {
          s.attr("class", clsValue.replace("placeholderfriend", ""));
        }
      }
    };

    //Determine if placeholder support is available.
    function isPlaceholer() {
      var input = document.createElement("input");
      return "placeholder" in input;
    }
    //Unsupported Codes
    if (!isPlaceholer()) {
      $(function() {
        var form = $(this);
        var elements = form.find("input[type='text'][placeholder]");
        elements.each(function() {
          var s = $(this);
          var pValue = s.attr("placeholder");
          var sValue = s.val();
          if (pValue) {
            if (sValue == "") {
              s.val(pValue);
            }
          }
        });

        elements.focus(function() {
          var s = $(this);
          var pValue = s.attr("placeholder");
          var sValue = s.val();
          if (sValue && pValue) {
            if (sValue == pValue) {
              s.val("");
            }
          }
        });

        elements.blur(function() {
          var s = $(this);
          var pValue = s.attr("placeholder");
          var sValue = s.val();
          if (!sValue) {
            s.val(pValue);
          }
        });

        var elementsPass = form.find("input[type='password'][placeholder]");
        elementsPass.each(function(i) {
          var s = $(this);
          var pValue = s.attr("placeholder");
          var sValue = s.val();
          if (pValue) {
            if (sValue == "") {
              var html = this.outerHTML || "";
              html = html
                .replace(
                  /\s*type=(['"])?password\1/gi,
                  " type=text placeholderfriend"
                )
                .replace(/\s*(?:value|on1[a-z]+|name)(=(['"])?\S*\1)?/gi, " ")
                .replace(
                  /\s*placeholderfriend/,
                  " placeholderfriend value='" +
                    pValue +
                    "' " +
                    "οnfοcus='placeholderfriendfocus(this);' "
                );
              var idValue = s.attr("id");
              if (idValue) {
                s.attr("id", idValue + "placeholderfriend");
              }
              var clsValue = s.attr("class");
              if (clsValue) {
                s.attr("class", clsValue + "placeholderfriend");
              }
              s.hide();
              s.after(html);
            }
          }
        });

        elementsPass.blur(function() {
          var s = $(this);
          var sValue = s.val();
          if (sValue == "") {
            var idValue = s.attr("id");
            if (idValue) {
              s.attr("id", idValue + "placeholderfriend");
            }
            var clsValue = s.attr("class");
            if (clsValue) {
              s.attr("class", clsValue + "placeholderfriend");
            }
            s.hide()
              .next()
              .show();
          }
        });
      });
    }
    window.placeholderfriendfocus = placeholderfriend.focus;
  });
}

Deconstruct PlaceholderInit function
on pages that need to display placeholders

import { PlaceholderInit } from '@/utils/placeholder'

Call this function before the page is displayed, so that the place where the current page needs to display placeholders will display
when the page comes in

PlaceholderInit();

If the input page of a new pop-up box needs to display placeholders, the function

will also be called when the new pop-up box is opened

If the request parameter supplied when requesting the interface is of type FormData, we can divide the operation into two ways.
The method in FormData()
0, append() append value
1, set() modify value
2, getAll() get all check box values
3, get() get radio box values
1. Ajax encapsulated by jQuery
If the request parameter is formdata, must set two configuration items
processData: false
contentType: false

  $.ajax({
            url: 'Interface Address',
            type: "POST",
            data: fd,
            success: function(res){

            },
            processData: false, //do not convert data request data (the object format is automatically converted to string format on request)
            contentType: false // do not set request header (FormData comes with request header)
        })

2. Native Ajax manipulation
If the request parameter is FormData, then post-style Ajax requests no longer need to set the request header

FormData:
	var form = $("form")[0];	//Converting jq objects to DOM objects (must be DOM objects)
	var fd = new FormData(form);
	
	
Native ajax:
 		var xhr = new XMLHttpRequest();
        xhr.open('POST', '/common/post'). xhr.onload = function () { var xhr.open('POST', '/common/post');
        xhr.open('POST', '/common/post'); xhr.onload = function () {
            console.log(this.response); // output the result
        }
        xhr.send(fd); //pass the data from the form to the backend

let self=this;
let date=new Date();

　　if(date.getHours()>=0&&date.getHours()<12){

　　　　self.hoursTip="Good morning"

　　}else if(date.getHours()>=12&&date.getHours()<18){

　　　　self.hoursTip="Good afternoon"

　　}else{

　　　　self.hoursTip="Good night"

　　}
}

Example:
		"()" | "()[]{}" | "{[]}"	true	{{{{}}}([])}
		"(]" | "([)]"	false				{{{{}}}([[])]}	{([)]}
		*/
		var str = "{{{{}}}([[])]}";
		var isValid = function(s){
			let items = []
			let sLength = s.length
			if(sLength % 2 !== 0){
				return false
			}
			for(let i=0; i < sLength; i++){
				switch(s[i]){
					case "(":
						items.push(s[i])
						break
					case "[":
						items.push(s[i])
						break
					case "{":
						items.push(s[i])
						break
					case ")":
						if(items[items.length - 1] === "("){
							items.pop()
						}
						break
					case "]":
						if(items[items.length - 1] === "["){
							items.pop()
						}
						break
					case "}":
						if(items[items.length - 1] === "{"){
							items.pop()
						}
						break
				}
			}
			return items.length === 0
		}
		console.log(isValid(str))

function.call(this, arg1, arg2, ...)

Application: The child constructor inherits the properties of the parent constructor

function Father (surname) {
    this.surname = surname;
}
function Son (surname) {
    // Changes this in the parent constructor to this in the child constructor, and passes a value to this attribute.
    Father.call(this, surname);
}
var xiaoming = new Son('xiao');

2. apply
Effect: Changes this point to call the function to pass in an argument.
Grammar:

function.apply(this, [arg1, arg2, ...])

Application: Call a method in Math

var arr = [1, 2, 3];
Math.max.apply(Math, arr);

3. bind
Effect: Change this point to pass in parameter.
Grammar:

function.bind(this, arg1, arg2, ...)

Application: Change the this pointer in setTimeout

var obj = {
    data: 'first',
    init: function () {
        setTimeout(function(){
            this.data = 'last';
        }.bind(this), 3000)
    }
}
obj.init();