Question

我正在尝试在RPI零上创建一个Clock / IN-Clock / OUT设备，该设备将具有2个用于进出时钟的物理按钮（红色和绿色），2X16 LCD显示屏和RFID读取器，它将将所有数据注册到mySQL DB，我创建的功能将不断：从RFID读取，检查按钮，以及将日期/时间显示到LCD，这就是为什么我使用多重处理并行化所有功能的原因问题是我无法将变量从一个函数传递给另一个函数

我尝试了全局变量-不走运

我试图将'return'放入readdb（）函数中，但这仅读取一次另外，如果我将readdb（）作为参数传递给p3 = Process（target = greenbutton，args =（readdb（），））程序将冻结

from multiprocessing import Process
import sys
import RPi.GPIO as GPIO
from mfrc522 import SimpleMFRC522
import MySQLdb
import I2C_LCD_driver
import time


mylcd = I2C_LCD_driver.lcd()
reader = SimpleMFRC522()
GPIO.setmode(GPIO.BCM)


def timedisplay():
    while True:
        mylcd.lcd_display_string("                ", 1)
        mylcd.lcd_display_string("Time: %s" %time.strftime("%H:%M"), 1)
        time.sleep(3)
        mylcd.lcd_display_string("                ", 1)
        mylcd.lcd_display_string("Date: %s" %time.strftime("%m/%d/%Y"), 1)
        time.sleep(3)


def readdb(): #will extract data from DB that coresponds to rfid key scaned

    while True:
        try:

               idc, text = reader.read()

        finally:
                GPIO.cleanup()

        # Open database connection
        db = MySQLdb.connect("localhost","pi","raspberry","mydb" )

        # prepare a cursor object using cursor() method
        cursor = db.cursor()

        sql = "SELECT * FROM staffs WHERE key_id = '%d'" %idc

        try:
           # Execute the SQL command
           cursor.execute(sql)
           # Fetch all the rows in a list of lists.
           results = cursor.fetchall()
           for row in results:
              #global idc
              idc = row[0]
              key_id = row[1]
              name = row[2]
              # Now print fetched result
              print "id=%s,key_id=%s,name=%s" % (idc, key_id, name,) #prints in console key data
              mylcd.lcd_display_string("                ", 2) #clears second row of lcd
              mylcd.lcd_display_string(name, 2) #prints nam from database 

        except:
           print "Error: unable to fecth data"

            # disconnect from server
        db.close()
        return idc


def greenbutton(v):
    GPIO.setup(27, GPIO.IN, pull_up_down=GPIO.PUD_UP)
    while True:
        input_state = GPIO.input(27)
        if input_state == False:
            mylcd.lcd_display_string("                ", 2)
            print('GREEN Button Pressed')
            time.sleep(0.2)
        if input_state == False:
            db = MySQLdb.connect("localhost","pi","raspberry","mydb" )

            # prepare a cursor object using cursor() method
            cursor = db.cursor()
            #v=readdb()
            sql = "INSERT INTO clocking (`staff_id`, `clock_in_flag`) VALUES ('%s','%d')" %(v, 1)

            try:
        # Execute the SQL command
                cursor.execute(sql)
                mylcd.lcd_display_string("Clocking IN", 2)
                time.sleep(3)
                mylcd.lcd_display_string("                ", 2)
            except:
                print "Error: unable to fecth data"

        # disconnect from server
            db.commit()
            db.close()
            #return

    #return   

def redbutton(v):
    GPIO.setup(22, GPIO.IN, pull_up_down=GPIO.PUD_UP)
    while True:
        input_state = GPIO.input(22)
        if input_state == False:
            mylcd.lcd_display_string("                ", 2)
            print('RED Button Pressed')
            time.sleep(0.2)
        if input_state == False:
            db = MySQLdb.connect("localhost","pi","raspberry","mydb" )

            # prepare a cursor object using cursor() method
            cursor = db.cursor()
            #v=readdb()
            sql = "INSERT INTO clocking (`staff_id`, `clock_in_flag`) VALUES ('%s','%d')" %(v, 0) 

            try:
        # Execute the SQL command
                cursor.execute(sql)
                mylcd.lcd_display_string("Clocking OUT", 2)
                time.sleep(3)
                mylcd.lcd_display_string("                ", 2)
            except:
                print "Error: unable to fecth data"

        # disconnect from server
            db.commit()
            db.close()


if __name__ == '__main__':

 while True:
  p1 = Process(target=timedisplay)
  p1.start()
  p2 = Process(target=readdb)
  p2.start()
  p3 = Process(target=greenbutton, args=(readdb(), )) # this way will not work
  p3.start()
  p4 = Process(target=redbutton, args=(1, )) # 1 is just for test and it works
  p4.start()
  p1.join()
  p2.join()
  p3.join()
  p4.join()

请给我建议我该如何解决

如何正确地将参数从多处理中的另一个函数传递给一个函数

0 个答案: