Raspberry-PI和Arduino与Python的串行通信

2024-03-28 21:49:08 发布

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我在Raspberry Pi(Python脚本)和Arduino nano/uno之间的串行通信有一些问题。我用USB端口连接两个设备,当我直接从arduino IDE串行监视器发送命令时,arduino草图始终正确响应:

<Arduino is ready>
<MSG:GDI,RESPONSE:EMD-1707-1993,Time:7>
<MSG:GDI,RESPONSE:EMD-1707-1993,Time:23>
<MSG:GDI,RESPONSE:EMD-1707-1993,Time:26>
<MSG:GDI,RESPONSE:EMD-1707-1993,Time:30>
<MSG:GDI,RESPONSE:EMD-1707-1993,Time:34>
<MSG:GDI,RESPONSE:EMD-1707-1993,Time:38>

但是,当我运行python脚本,并且他发送相同的命令时,草图以随机方式响应。在

覆盆子终端:

^{pr2}$

Arduino串行监视器:

<Arduino is ready>
MGIRSPi35

Mi代码为:

Arduino素描:

#include <EEPROM.h>

#define DEVICE_BAUD_RATE        9600

#define EEPROM_SIZE             1024

#define ID_PREFIX               "EMD-"

#define MSG_START_CHAR          '<'
#define MSG_END_CHAR            '>'

#define MSG_GET_DEVICE_ID       "GDI"

const byte buffSize = 40;
char inputBuffer[buffSize];
byte bytesRecvd = 0;
boolean readInProgress = false;
boolean newMsg = false;

char cmd[buffSize] = {0};
int pin = 0;
int value = 0;

unsigned long curMillis;

void setup() {
  if(getDeviceId() == "") {
    setDeviceId();
  }

  Serial.begin(DEVICE_BAUD_RATE);

  while(!Serial) {
    ;
  }

  Serial.println("<Arduino is ready>");
}

void loop() {
  curMillis = millis();
  readMsg();
  processCommand();
}

void readMsg() {
  if(Serial.available() > 0) {
    char x = Serial.read();

    if(x == MSG_END_CHAR) {
      readInProgress = false;
      newMsg = true;
      inputBuffer[bytesRecvd] = 0;
      strcpy(cmd, inputBuffer);
    }

    if(readInProgress) {
      inputBuffer[bytesRecvd] = x;
      bytesRecvd++;

      if(bytesRecvd == buffSize) {
        bytesRecvd = buffSize - 1;
      }
    }

    if(x == MSG_START_CHAR) { 
      bytesRecvd = 0; 
      readInProgress = true;
    }
  }
}

void processCommand() {
  if(strcmp(cmd, MSG_GET_DEVICE_ID) == 0) {
    sendMsg(getDeviceId());
  } else {
    sendMsg("Command Not Found");
  }
}

void sendMsg(String response) {
  if(newMsg) {
    newMsg = false;
    Serial.print("<MSG:");
    Serial.print(cmd);
    Serial.print(",RESPONSE:");
    Serial.print(response);
    Serial.print(",Time:");
    Serial.print(curMillis >> 9);
    Serial.println(">");
  }
}

String getDeviceId() {
  String id = "";

  for(int i=0; i<EEPROM_SIZE; i++) {
    int value = EEPROM.read(i);

    if(value == 0xFF) {
      return id;
    }

    id += char(value);
  }

  return id;
}

void setDeviceId() {
  randomSeed(analogRead(0));

  String id = ID_PREFIX + String(random(1000, 10000)) + "-" + String(random(1000, 10000));

  for(int i=0; i<EEPROM_SIZE; i++) {
    EEPROM.write(i, i<id.length() ? id.charAt(i) : 0xFF);
  }
}

Python脚本:

#!/usr/bin/python
import os
import serial

MSG_START_CHAR              = '<'
MSG_END_CHAR                = '>'

MSG_GET_DEVICE_ID           = 'GDI'


def read_from_device(serial_connection):  
    response = ""
    current_char = "z"

    while ord(current_char) != MSG_START_CHAR: 
        current_char = serial_connection.read()

    while ord(current_char) != MSG_START_CHAR:
        if ord(current_char) != MSG_START_CHAR:
            response = response + current_char 

        current_char = serial_connection.read()

    return(response)

def write_to_device(serial_connection, msg):
    cmd = MSG_START_CHAR + msg + MSG_END_CHAR

    print(cmd)

    serial_connection.write(cmd)

with serial.Serial('/dev/ttyACM0', 9600, timeout=10) as serial_connection:
    waiting_for_reply = False

    if waiting_for_reply == False:
        print('Sending {0} command to device...'.format(MSG_GET_DEVICE_ID))

        write_to_device(serial_connection, MSG_GET_DEVICE_ID)

        waiting_for_reply = True

    if waiting_for_reply == True:
        while serial_connection.inWaiting() == 0:
            pass

        response = read_from_device(serial_connection)

        print('Reply Received: {0}'.format(response))

        waiting_for_reply = False

    serial_connection.close()

Tags: idiftimeresponsedeviceserialmsgconnection
1条回答
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1楼 · 发布于 2024-03-28 21:49:08

问题是你在比较一个int和一个字符串。在函数read_from_device中,这行:

    while ord(current_char) != MSG_START_CHAR: 
  • current_char是一个字符串。在
  • ord(current_char)是一个整数(实际上是一个字符串的ASCII值)。在
  • MSG_START_CHAR是一个字符串。在

因此比较的是int和string。这将始终为False,因此while循环将永远不会退出。最终Arduino不再有字符了,此时您将对空字符串执行ord()。这是不允许的,所以你在那一点上得到了回溯。在

你根本不需要ord函数。在Python中,您只需直接处理字符串。在

试试这个:

^{pr2}$

有一件事我不知道:Arduino正在发送单字节字符。在Python3中(如果您使用的是这个),所有字符都是unicode。我不知道序列库会怎么处理。在

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