树莓派python485设备通信
1.简单概述程序设计
树莓派通过Modbus-Rtu协议采集温湿度传感器数据和门磁状态，控制继电器动作。
本demo完整工程
2.编程逻辑分析
在temp_hum_door.py整个控制逻辑在文件中实现：
# -*- coding: utf-8 -*- from new_relay_control import relay from time import sleep #温湿度获取 def temp_hum_sensor_get(): temp_hum = relay() temp_hum.all_relay = 3 temp_hum.relay_all_on_order = ['01 04 00 00 00 02 71 CB'] return_str = temp_hum.ALL_ON() return return_str #获取门磁开关 def door_sensor_get(): door_sensor = relay() door_sensor.all_relay = 3 door_sensor.relay_all_on_order = ['FE 01 00 00 00 02 A9 C4'] return_str = door_sensor.ALL_ON() return return_str id_value =2 action =1 time = 1 if id_value == 1: relay_open = relay() if action == 1: return_str = relay_open.ALL_ON() else: return_str = relay_open.ALL_OFF() relay_str = return_str[8:12] if relay_str == "FF00": relay_state = 1 else: relay_state = 0 print(relay_str) print(relay_state) if id_value == 2: while True: return_str = temp_hum_sensor_get() print(return_str) get_str1 = return_str[6:10] get_str2 = return_str[10:14] try: temp_data = (int(get_str1, 16)) / 10 hum_data = (int(get_str2, 16)) / 10 except ValueError: pass final_str2 = get_str1 ' ' get_str2 print(final_str2) print(temp_data) print(hum_data) sleep(time) if id_value == 3: while True: return_str = door_sensor_get() get_str3 = return_str[6:8] print(get_str3) sleep(time) - 这三个值可以自己控制，id_value=1.执行继电器动作；id_value=二、循环获取温湿度数据；id_value=3.循环获取门磁开关状态。
- action=一、打开继电器；action=关闭继电器。
- time = 1，表示每隔1s读取温湿度或门磁开关数据。
id_value =2 action =1 time = 1 温湿度获取函数：
def temp_hum_sensor_get(): temp_hum = relay() temp_hum.all_relay = 3 temp_hum.relay_all_on_order = ['01 04 00 00 00 02 71 CB'] return_str = temp_hum.ALL_ON() return return_str 门磁开关获取函数：
def door_sensor_get(): door_sensor = relay() door_sensor.all_relay = 3 door_sensor.relay_all_on_order = ['FE 01 00 00 00 02 A9 C4'] return_str = door_sensor.ALL_ON() return return_str - 使用class定义类，实现继电的控制逻辑。类里面定义了串口收发的函数relay_send(self, send_order)以及继电器打开与关闭的控制逻辑。
# -*- coding: utf-8 -*-
import RPi.GPIO as GPIO
import serial
from time import sleep
'''2路继电器开关控制函数，单独继电器开关控制和全部开关控制'''
class relay(object):
def __init__(self):
self.relay_all_on_order = ['02 05 00 00 FF 00 8C 09', '02 05 00 01 FF 00 DD C9',
'02 0F 00 00 00 08 01 FF FE C0']
self.relay_all_off_order = ['02 05 00 00 00 00 CD F9', '02 05 00 01 00 00 9C 39',
'02 0F 00 00 00 08 01 00 BE 80']
self.relay1 = 1
self.relay2 = 2
self.all_relay = 3
self.port = '/dev/ttyAMA0'
def relay_send(self, send_order):
if self.port:
relay_serial = serial.Serial(self.port, 9600)
GPIO.setmode(GPIO.BCM)
GPIO.setup(17, GPIO.OUT)
if not relay_serial.isOpen():
relay_serial.Open()
while True:
GPIO.output(17, GPIO.HIGH)
sleep(0.01)
relay_serial.write(bytes.fromhex(send_order))
# relay_serial.write(bytes(send_order))
sleep(0.01)
GPIO.output(17, GPIO.LOW)
count = relay_serial.inWaiting()
if count > 0:
GPIO.output(17, GPIO.LOW)
sleep(0.01)
recv = relay_serial.read(count)
GPIO.output(17, GPIO.HIGH)
sleep(0.01)
print("recv: ", recv)
# recv_bytes = binascii.b2a_hex(recv)
# recv_str = binascii.b2a_hex(recv_bytes).decode('utf-8')
recv_str = str(recv.hex())
print("recv_str: ", recv_str)
if recv_str == "00":
print("error")
else:
return recv_str
sleep(0.5)
def ALL_ON(self):
send_order = self.relay_all_on_order[self.all_relay - 3]
print(send_order)
get_return = self.relay_send(send_order)
return get_return
def ALL_OFF(self):
send_order = self.relay_all_off_order[self.all_relay - 3]
get_return = self.relay_send(send_order)
print("继电器控制: ALL_RELAY_OFF")
return get_return
def RELAY1_ON(self):
send_order = self.relay_all_on_order[self.relay1 - 1]
get_return = self.relay_send(send_order)
print("继电器控制: RELAY1_ON")
return get_return
def RELAY1_OFF(self):
send_order = self.relay_all_off_order[self.relay1 - 1]
get_return = self.relay_send(send_order)
print("继电器控制: RELAY1_OFF")
return get_return
def RELAY2_ON(self):
send_order = self.relay_all_on_order[self.relay2 - 1]
get_return = self.relay_send(send_order)
print("继电器控制: RELAY2_ON")
return get_return
def RELAY2_OFF(self):
send_order = self.relay_all_off_order[self.relay2 - 1]
get_return = self.relay_send(send_order)
print("继电器控制: RELAY2_OFF")
return get_return
串口发送与接收函数：
- 采用的485转TTL模块，DIR脚控制接收与发送。当DIR高电平的时候为发送模式，当DIR为低电平的时候为接收模式。
- DIR脚采用GPIO管脚控制即可。
def relay_send(self, send_order):
if self.port:
relay_serial = serial.Serial(self.port, 9600)
GPIO.setmode(GPIO.BCM)
GPIO.setup(17, GPIO.OUT)
if not relay_serial.isOpen():
relay_serial.Open()
while True:
GPIO.output(17, GPIO.HIGH)
sleep(0.01)
relay_serial.write(bytes.fromhex(send_order))
# relay_serial.write(bytes(send_order))
sleep(0.01)
GPIO.output(17, GPIO.LOW)
count = relay_serial.inWaiting()
if count > 0:
GPIO.output(17, GPIO.LOW)
sleep(0.01)
recv = relay_serial.read(count)
GPIO.output(17, GPIO.HIGH)
sleep(0.01)
print("recv: ", recv)
# recv_bytes = binascii.b2a_hex(recv)
# recv_str = binascii.b2a_hex(recv_bytes).decode('utf-8')
recv_str = str(recv.hex())
print("recv_str: ", recv_str)
if recv_str == "00":
print("error")
else:
return recv_str
sleep(0.5)
该函数在类实例化时会自动调用。（两路继电器的控制指令，串口端口的设置等）
def __init__(self):
self.relay_all_on_order = ['02 05 00 00 FF 00 8C 09', '02 05 00 01 FF 00 DD C9',
'02 0F 00 00 00 08 01 FF FE C0']
self.relay_all_off_order = ['02 05 00 00 00 00 CD F9', '02 05 00 01 00 00 9C 39',
'02 0F 00 00 00 08 01 00 BE 80']
self.relay1 = 1
self.relay2 = 2
self.all_relay = 3
self.port = '/dev/ttyAMA0'
3、调试过程中注意事项
子设备通信程序需要在python3以上版本进行编译运行，如果低版本，编译运行时会报错。 有些写法，低版本的不支持。例如下面写法，python2.7版本会报错，python3以上版本则不会。
temp_value = int(get_str1, 16)
hum_value = int(get_str2, 16)
下面编码声明在python3以上版本则不用，在低版本需要声明，不然运行会报错。
# -*- coding: utf-8 -*-
下面写法同样在python3以上版本适用，在低版本中则不支持，不然运行会报错。
recv_str = str(recv.hex())
若在程序中遇到异常，可以添加捕获异常处理。