import os
import datetime

import can #需要安装python-can库  pip install python-can
from can import bus

speed=0
def sped():
    global speed
    bus.set_filters=[{"can_id": 0x4f2, "can_mask": 0xFFFF, "extended": False}]
    #连接can1

    can1 = can.interface.Bus(channel = 'can0', bustype = 'socketcan',can_filters=bus.set_filters) #python-can 4.0需要用这个
    # can1 = can.interface.Bus(channel = 'can0', bustype = 'socketcan') #python-can 4.0需要用这个
    #一直循环接收数据
    a = 1
    while a == 1 :
        msg = can1.recv(3.0) #recv()中定义超时接收时间
        # print(msg)
        b = str(msg).replace(' ', '')
        c = b.find('ID')
        d = b.find('DL')
        e = b[c + 3:c + 7]  # id
        # print(b, '\n')
        if e == '04f2':
            # print('成功接收到速度报文：04f2   接收时间为：',datetime.datetime.now())
            speed16 = b[d + 6:d + 10]
            # print('接收到的速度16进制为：', speed16)  # 速度
            speed10 = int(speed16, 16)
            speed = speed10 * 0.01
            # print('接收到的速度10进制为：', speed10)
            # print('接收到的表显速度为：%skm/h' % speed, '\n')
            # file = open('speed.txt', 'a')
            # file.write(str(speed))
            # file.write('\n')

        else:
            print('未接收到速度报文')

        #关闭can
        # os.system('sudo ifconfig can1 down')