Raspberry Pi 和 Arduino 之间的简单 2 路串行通信

Posted 2023-02-16

【中文标题】Raspberry Pi 和 Arduino 之间的简单 2 路串行通信

【英文标题】：Simple 2-way serial communication between Raspberry Pi and Arduino

【发布时间】：2018-07-31 15:10:37

【问题描述】：

我想在我的 Raspberry Pi 和我的 Arduino 之间进行简单的 2 路串行通信。这是一个项目，我将用另一个我还没有的串行设备替换 Arduino。

我已经完成了从 Arduino 到 Raspberry Pi 的单向通信 (https://maker.pro/raspberry-pi/tutorial/how-to-connect-and-interface-raspberry-pi-with-arduino)，但是在使用 2-way 时遇到了一点麻烦。我使用的 Arduino 代码来自这个例子：https://www.arduino.cc/en/Serial/Read:

int incomingByte = 0;   // for incoming serial data

void setup() 
        Serial.begin(9600);     // opens serial port, sets data rate to 9600 bps


void loop() 

        // send data only when you receive data:
        if (Serial.available() > 0) 
                // read the incoming byte:
                incomingByte = Serial.read();

                // say what you got:
                Serial.print("I received: ");
                Serial.println(incomingByte, DEC);
        

而我使用的 Python 代码是这样的：

import serial
import time
ser = serial.Serial('/dev/ttyACM1',9600)
var1 = "3"
while True:
    ser.write(var1.encode())
    time.sleep(0.2)
    read_serial=ser.readline()
    print read_serial

通过网络查看后，我将要发送的值从 ser.write('3') 更改为字符串 'var1' 并在之后放置 '.encode()' 以便编码为字节。没有错误出现，但没有任何事情发生/正在被写出。

这样做的目的是让 Raspberry Pi 向 Arduino 发送一个“3”，而 Arduino 以“我收到：3”作为响应，这应该打印在 Raspberry Pi/Python 的终端窗口中。从那里我想我可以让它更复杂地实现我发送这样一个命令的目标：'0 30 50 100'，我没有的设备会响应。

感谢您的帮助。谢谢。

【问题讨论】：

尝试在ser.write 行之后添加延迟

到目前为止，您只显示了 RasPi 代码。但是需要两个人沟通。因此，了解 Arduino 的功能也很重要。 Arduino 如何读取 RasPi 发送给它的内容？它是否在等待 RasPi 未发送的终结符（\r 或 \n）？

Arduino 代码取自 Arduino 网站链接的示例。

所以，我添加了延迟，但仍然没有任何反应。

【参考方案1】：

我迟到了，但我希望这对其他人有所帮助。 我试图进行双向通信，我可以从双方发送和接收字符串数据，这就是我所做的：- Arduino方面：-

void setup() 
   Serial.begin(9600); // begin transmission

void loop() 
  String val;
  while (Serial.available() > 0) 
    val = val + (char)Serial.read(); // read data byte by byte and store it
  
  Serial.print(val); // send the received data back to raspberry pi

在覆盆子方面我有（python）：-

import serial
port = "/dev/ttyACM0"#put your port here
baudrate = 9600
ser = serial.Serial(port, baudrate)
def tell(msg):
    msg = msg + '\n'
    x = msg.encode('ascii') # encode n send
    ser.write(x)

def hear():
    msg = ser.read_until() # read until a new line
    mystring = msg.decode('ascii')  # decode n return 
    return mystring

while True:
    val = input() # take user input
    tell(val) # send it to arduino
    var = hear() # listen to arduino
    print(var) #print what arduino sent

我希望很清楚 Arduino 从树莓派收到消息并将同样的信息发送回 Arduino。同样，你可以用它做一些其他的事情。

【参考方案2】：

在我的项目中，我的目标是通过串行接口在 Arduino 和 Raspberry Pi 之间建立双向数据交换。 Raspberry Pi 发送 Arduino 命令执行，Arduino 发送 Raspberry Pi 传感器读数（当前为随机数）。

目前，该项目包括两个用 Python 编写的 Raspberry Pi 脚本和一个 Arduino 程序。 Raspberry Pi 的第一个脚本使用 URWID 库组织图形界面和命令输入，第二个脚本用于与串行端口通信。来源如下。操作的结果中规中矩，但也许是我做错了什么？这个问题的解决方法正确吗？

Arduino 软件：

#define SERIAL_SPEED 19200 // the speed of the serial port
#define READ_SENSOR_INTERVAL 1000UL  // frequency of output to the serial port 

int IN1 = 7; 
int IN2 = 6;
int IN3 = 5;
int IN4 = 4;
int ENA = 9;
int ENB = 3;

char command     = 'S';
char prevCommand = 'A';
int velocity = (4 + 1) * 10 + 100; // the fill factor of the PWM

unsigned long timer0 = 2000; 
unsigned long timer1 = 0;    

long randNumber;
long myflag = 0;

void setup() 
  Serial.begin(SERIAL_SPEED);
  pinMode (ENA, OUTPUT);
  pinMode (IN1, OUTPUT);
  pinMode (IN2, OUTPUT);
  pinMode (ENB, OUTPUT);
  pinMode (IN4, OUTPUT);
  pinMode (IN3, OUTPUT);


void loop()

  static unsigned long prevSensorTime = 0;
  if (millis() - prevSensorTime > READ_SENSOR_INTERVAL) 
    prevSensorTime = millis();
    if (myflag == 1)
    
      randNumber = random(300);
      Serial.print(command);
      Serial.println(randNumber);
    
  


  if (Serial.available() > 0) 
    timer1 = millis();
    prevCommand = command;
    command = Serial.read();
    myflag = 1;
    if (command != prevCommand) 
      switch (command) 
        case 'W':
          // Вперёд
          analogWrite(ENA, 0);
          analogWrite(ENB, 0);
          delay(20);
          digitalWrite (IN2, LOW);
          digitalWrite (IN1, HIGH);
          digitalWrite (IN4, LOW);
          digitalWrite (IN3, HIGH);
          analogWrite(ENA, velocity);
          analogWrite(ENB, velocity);

          break;
        case 'A':
          analogWrite(ENA, 0);
          analogWrite(ENB, 0);
          delay(20);
          digitalWrite (IN2, LOW);
          digitalWrite (IN1, HIGH);
          digitalWrite (IN4, HIGH);
          digitalWrite (IN3, LOW);
          analogWrite(ENA, velocity);
          analogWrite(ENB, velocity);
          break;
        case 'S':
          analogWrite(ENA, 0);
          analogWrite(ENB, 0);
          delay(20);
          digitalWrite (IN2, HIGH);
          digitalWrite (IN1, LOW);
          digitalWrite (IN4, HIGH);
          digitalWrite (IN3, LOW);

          analogWrite(ENA, velocity);
          analogWrite(ENB, velocity);
          break;
        case 'D':
          analogWrite(ENA, 0);
          analogWrite(ENB, 0);
          delay(20);
          // A
          digitalWrite (IN2, HIGH);
          digitalWrite (IN1, LOW);
          // B
          digitalWrite (IN4, LOW);
          digitalWrite (IN3, HIGH);
          analogWrite(ENA, velocity);
          analogWrite(ENB, velocity);
          break;
        case ' ': 
          //velocity = 0;
          analogWrite(ENA, 0);
          analogWrite(ENB, 0);
          break;
        default:  
          if ((command >= 48) && (command <= 57)) 
            if (command == 48)
            
              velocity = 0;
            
            else
            
              velocity = (command - 48 + 1) * 10 + 100;
            
          
      
     
  
  else 
    timer0 = millis();  // Получение текущего времени
    if ((unsigned long)(timer0 - timer1) > 20000) 
      analogWrite(ENA, 0);
      analogWrite(ENB, 0);
      prevCommand = ' ';
    
  

Python GUI 脚本

from __future__ import print_function, absolute_import, division
import subprocess
import urwid
import serial
from subprocess import Popen, PIPE
from time import sleep


def exit_on_q(key):
    global power
    global ser
    global spower
    global p
    global currc

    if key in ('q', 'Q'):
        p.stdin.write(b'Q\n')
        p.stdin.flush()
        sleep(1)
        raise urwid.ExitMainLoop()


    if key in ('w', 'W'):
    # forward
        currc = 'W - Forward'
        p.stdin.write(b'W\n')
        p.stdin.flush()

    if key in ('a', 'A'):
    # Left
        currc = 'A - Left'
        p.stdin.write(b'A\n')
        p.stdin.flush()

    if key in ('s', 'S'):
    # Backward
        currc = 'S - Backward'
        p.stdin.write(b'S\n')
        p.stdin.flush()

    if key in ('d', 'D'):
    # Right
        currc = 'D - Right'
        p.stdin.write(b'D\n')
        p.stdin.flush()


    if key in (' '):
    # Stop
        currc = 'Space - Stop'
        p.stdin.write(b' \n')
        p.stdin.flush()

    if key in ('+'):
        if (power < 99):
            power = power + 10 
            spower = spower + 1
            txt_CP.set_text(('banner', str(power)))

    if key in ('-'):
        if (power > 0):
            power = power - 10
            spower = spower - 1
            txt_CP.set_text(('banner', str(power)))

    txt_CCV.set_text(('banner', currc))

def enter_idle():
    loop.remove_watch_file(pipe.stdout)

def update_text(read_data):
    txt_Q.set_text(('banner', read_data))

if __name__ == '__main__':

    currc = "No command"

    palette = [
        ('banner', 'black', 'light gray'),
        ('streak', 'black', 'dark blue'),
        ('bg', 'black', 'dark blue'),]

    # spower = 0..9 (48 .. 57)
    spower = 4
    power = spower * 10

    txt_F = urwid.Text(('banner', u"W - Forward (\u2191)"), align='center')
    txt_LRS = urwid.Text(('banner', u"\u2190 A - Left | Space - Stop | D - Right \u2192"), align='center')
    txt_B = urwid.Text(('banner', u"S - Backward (\u2193)"), align='center')
    txt_P = urwid.Text(('banner', u"'+' Increase motor power | '-' Decrease motor power"), align='center')
    txt_C = urwid.Text(('banner', u"Current power:"), align='center')

    txt_CP = urwid.Text(('banner', str(power)), align='center')

    # current command
    txt_CC = urwid.Text(('banner', u"Current command: "), align='center')
    txt_CCV = urwid.Text(('banner', u"No command"), align='center')

    txt_Log = urwid.Text(('banner', u"Log: "), align='center')
    txt_LogV = urwid.Text(('banner', u""), align='center')

    txt_Q = urwid.Text(('banner', u"Q - Quit"), align='center')

    #empty string
    txt_E = urwid.Text(('banner', u""), align='center')

    pile = urwid.Pile([txt_F, txt_LRS, txt_B, txt_E, txt_P, txt_C, txt_CP, txt_E, txt_CC, txt_CCV, txt_E, txt_Log, txt_LogV, txt_E, txt_Q ])
    top = urwid.Filler(pile, top = 5)


    loop = urwid.MainLoop(top, palette, unhandled_input=exit_on_q, handle_mouse=False)

    stdout = loop.watch_pipe(update_text)
    stderr = loop.watch_pipe(update_text)   
    p = subprocess.Popen(['python3', 'shell_edt.py'], stdin = PIPE, stdout = stdout, stderr = stdout, shell = False)    
    loop.run()

Python 通信脚本

import sys
import threading
import serial
from time import sleep

global currcomm

readtimer = 1 # 


def read():
    global serialport
    global currcomm

    threading.Timer(readtimer, read).start()

    if (currcomm != -1):
        data = serialport.read(10);
        print(str(data) + " : "  + str(len(data)))
        sys.stdout.flush();
        #sleep(0.5)     '''     


serialport = serial.Serial("/dev/ttyACM0", 19200, timeout=0.2)
data = serialport.read(100);


currcomm = -1

threading.Timer(readtimer, read).start()
sleep(1)

while True:
    currcomm = input()

    if (currcomm == 'S') or (currcomm == 'D') or (currcomm == 'W') or (currcomm == 'A') or (currcomm == ' '):
        serialport.write(bytes(currcomm, encoding = 'utf-8'));
    if (currcomm == 'Q'):
        serialport.close() # Only executes once the loop exits