Question

我的脚本将传感器信息（温度，湿度，气压）打印到LCD屏幕上，还通过Flask RESTful api将其作为JSON发送给其他设备使用。下面的python脚本可以正常运行，但是只能运行一次，并且传感器信息永远不会更新。

如何每隔30秒刷新一次RESTful api上的JSON？（脚本最重要的元素在底部）。我试图将TempHum类放入while循环中，但是RESTful api根本不喜欢这种方式。我的问题也是如何循环脚本，以便仅JSON更新。我应该在哪里添加while循环或同等功能。

from flask import Flask
from flask_restful import Resource, Api
from Adafruit_BME280 import *
import RPi.GPIO as GPIO
import math, decimal
from datetime import datetime
import time

# Define GPIO to LCD mapping
LCD_RS = 7
LCD_E  = 8
LCD_D4 = 25
LCD_D5 = 24
LCD_D6 = 23
LCD_D7 = 18
LED_ON = 15

# Define some device constants
LCD_WIDTH = 20    # Maximum characters per line
LCD_CHR = True
LCD_CMD = False

LCD_LINE_1 = 0x80 # LCD RAM address for the 1st line
LCD_LINE_2 = 0xC0 # LCD RAM address for the 2nd line
LCD_LINE_3 = 0x94 # LCD RAM address for the 3rd line
LCD_LINE_4 = 0xD4 # LCD RAM address for the 4th line

# Timing constants
E_PULSE = 0.0005
E_DELAY = 0.0005

# Main program block

GPIO.setwarnings(False)
GPIO.setmode(GPIO.BCM)       # Use BCM GPIO numbers
GPIO.setup(17, GPIO.IN)      # Pin 17 for reset
GPIO.setup(LCD_E, GPIO.OUT)  # E
GPIO.setup(LCD_RS, GPIO.OUT) # RS
GPIO.setup(LCD_D4, GPIO.OUT) # DB4
GPIO.setup(LCD_D5, GPIO.OUT) # DB5
GPIO.setup(LCD_D6, GPIO.OUT) # DB6
GPIO.setup(LCD_D7, GPIO.OUT) # DB7
GPIO.setup(LED_ON, GPIO.OUT) # Backlight enable

sensor = BME280(mode=BME280_OSAMPLE_8)
in_degrees = sensor.read_temperature()
in_pascals = sensor.read_pressure()
in_hectopascals = in_pascals / 100
in_kilopascals = in_hectopascals / 10
in_humidity = sensor.read_humidity()
in_degrees_short = int(round(sensor.read_temperature(), 1))
in_degrees_short_f = (int(round(sensor.read_temperature(), 1)) * 1.8) + 32
in_humidity_short = int(round(sensor.read_humidity(), 1))

app = Flask(__name__)
api = Api(app)

def sleep():
        time.sleep(5)

def lcd_init():
  # Initialise display
  lcd_byte(0x33,LCD_CMD) # 110011 Initialise
  lcd_byte(0x32,LCD_CMD) # 110010 Initialise
  lcd_byte(0x06,LCD_CMD) # 000110 Cursor move direction
  lcd_byte(0x0C,LCD_CMD) # 001100 Display On,Cursor Off, Blink Off
  lcd_byte(0x28,LCD_CMD) # 101000 Data length, number of lines, font size
  lcd_byte(0x01,LCD_CMD) # 000001 Clear display
  time.sleep(E_DELAY)

def lcd_byte(bits, mode):
  # Send byte to data pins
  # bits = data
  # mode = True  for character
  #        False for command

  GPIO.output(LCD_RS, mode) # RS

  # High bits
  GPIO.output(LCD_D4, False)
  GPIO.output(LCD_D5, False)
  GPIO.output(LCD_D6, False)
  GPIO.output(LCD_D7, False)
  if bits&0x10==0x10:
    GPIO.output(LCD_D4, True)
  if bits&0x20==0x20:
    GPIO.output(LCD_D5, True)
  if bits&0x40==0x40:
    GPIO.output(LCD_D6, True)
  if bits&0x80==0x80:
    GPIO.output(LCD_D7, True)

  # Toggle 'Enable' pin
  lcd_toggle_enable()

  # Low bits
  GPIO.output(LCD_D4, False)
  GPIO.output(LCD_D5, False)
  GPIO.output(LCD_D6, False)
  GPIO.output(LCD_D7, False)
  if bits&0x01==0x01:
    GPIO.output(LCD_D4, True)
  if bits&0x02==0x02:
    GPIO.output(LCD_D5, True)
  if bits&0x04==0x04:
    GPIO.output(LCD_D6, True)
  if bits&0x08==0x08:
    GPIO.output(LCD_D7, True)

  # Toggle 'Enable' pin
  lcd_toggle_enable()

def lcd_toggle_enable():
  # Toggle enable
  time.sleep(E_DELAY)
  GPIO.output(LCD_E, True)
  time.sleep(E_PULSE)
  GPIO.output(LCD_E, False)
  time.sleep(E_DELAY)

def lcd_string(message,line,style):
  # Send string to display
  # Style=1 Left justified
  # Style=2 Centred
  # Style=3 Right justified

  if style==1:
          message = message.ljust(LCD_WIDTH, " ")
  elif style==2:
          message = message.center(LCD_WIDTH, " ")
  elif style==3:
          message = message.rjust(LCD_WIDTH, " ")

  message = message.ljust(LCD_WIDTH," ")

  lcd_byte(line, LCD_CMD)

  for i in range(LCD_WIDTH):
    lcd_byte(ord(message[i]),LCD_CHR)

def lcd_backlight(flag):
        #Toggle backlight on-off-on
        GPIO.output(LED_ON, flag)

class TempHum(Resource):
    lcd_init()
    lcd_string("Temperature: " + str(round(sensor.read_temperature(), 1)) + "C",LCD_LINE_1,2) 
    lcd_string("Humidity: " + str(round(sensor.read_humidity(), 1)) + "% ",LCD_LINE_2,2)
    lcd_string("Pressure: " + str(round(in_kilopascals, 1)) + "kPa",LCD_LINE_3,2)
    def get(self):
         temp = round(in_degrees, 1)
         humi = round(in_humidity, 1)
         pres = round(in_kilopascals, 1)
         return {'Temperature' : temp,
                 'Humidity' : humi,
                 'Pressure' : pres 
                 }

api.add_resource(TempHum, '/') 

if __name__ == "__main__":
    app.run(host='0.0.0.0', port=5000, debug=True)

Answer 1

如果您希望针对API的每个GET请求更新数据，则需要将所有sensor.read_*方法调用移至get函数中。因此，每次发出请求时都要读取传感器。

要刷新图表或网页，请在UI而不是服务器代码中放置循环。关于LCD屏幕，这可能是一个循环，但是您应该使用与Flask不同的线程

在Flask RESTful上刷新JSON

1 个答案: