如何让通过串口发送的Python数据等待Arduino完成当前任务？

Question

我正在尝试让我的Arduino微控制器和Mac电脑进行通信，并且已经建立了一个可以正常工作的串口连接。我的电脑正在向Arduino发送数据，而Arduino在准备好接收新数据时会发送一个'1'。

我创建了一个if-else语句（下面是Python脚本），这个语句要么向Arduino发送一行新数据，要么等待Arduino准备好接收新数据。

问题是，在Python脚本的第一部分，ser.read()总是返回'1'，这意味着脚本发送数据的速度比Arduino连接的步进电机反应的速度要快。

在Arduino的脚本中，你可以看到我在serialEvent()函数的第一行发送了状态信息，这在我看来应该让Arduino完成它的工作，然后再接收新的“任务”。但是，不知道为什么，这并没有成功。有没有人能帮我解决这个问题？

Python脚本

import os
import time
import serial

# Name of csv file with drawing coordinates
csvFile = "scaled_coordinates.csv"

# Create serial connection
ser = serial.Serial(port='/dev/tty.usbserial-A9005bDh', baudrate=9600)

wd = os.getcwd()
myFile = open(wd + "/coordinates/" + csvFile)

state = '1'

while True: # Exits when there is no more lines to read

    if state == '0': # Wait for Arduino to be ready
        state = ser.read()

    elif state == '1': # Send one more line to Arduino
        line = myFile.readline()
        if not line:
            break
        print line
        ser.write(line)
        #time.sleep(1)

        state = '0' # Wait for Arduino before reading next line

myFile.close

Arduino loop函数

void loop() {

  serialEvent(); // Call the serial function

  if (coord_complete) {

    // Steps to move from currrent to new point
    target1 = steps(x_current, y_current, x_new, y_new, 1);
    target2 = steps(x_current, y_current, x_new, y_new, 2);

    // Start moving
    stepper1.move(target1);
    stepper2.move(target2);

    // Update current position
    x_current = x_new;
    y_current = y_new;

    // Reset variables
    x_complete = false;
    y_complete = false;
    coord_complete = false;
  }

  // Stay in while loop until steppermotors is done
  while ((stepper1.distanceToGo() != 0) && (stepper2.distanceToGo() != 0)) {
    stepper1.run();
    stepper2.run();
  }
}

Arduino serialEvent函数

void serialEvent() {

  Serial.write('1'); // Tell Python that Arduino is ready for one more line

  while (Serial.available() && coord_complete == false) {
    char ch = Serial.read(); // Get new character
    Serial.print(ch);

    // If digit; add it to coord_string
    if (isDigit(ch)) {
      coord_string[index++] = ch;

    // Else if ch is ","; then rename to x_new
    } else if (ch == ',') {
      coord_string[index++] = NULL;                   // Finish coord_string
      x_new = atoi(coord_string);                     // Convert to integer
      x_complete = true;                              // Change x_complete to true
      index = 0;                                      // Reset index
      memset(coord_string, 0, sizeof(coord_string));  // Reset coord_string

    // Else if ch is a new line; then rename as y_new
    } else if (ch == ';') {
      //Serial.write('0');
      coord_string[index++] = NULL;
      y_new = atoi(coord_string);
      y_complete = true;
      index = 0;
      memset(coord_string, 0, sizeof(coord_string));
    }

    // Ends while-loop when true
    coord_complete = x_complete * y_complete;
  }
}

编辑

当前的Python代码如下：

import os
import time
import serial

# Name of csv file with drawing coordinates
csvGraphic = "Scaled_coordinates.csv"

# Create serial connection
ser = serial.Serial(port='/dev/tty.usbserial-A9005bDh', baudrate=9600)

wd = os.getcwd()
myFile = open(wd + "/graphics/" + csvGraphic)

state = '1'

while True: # Exits when there is no more lines to read

  print "state", state

  if state == '0': # Wait for Arduino to be ready
    state = str(ser.read())

  elif state == '1': # Send one more line to Arduino
    line = myFile.readline()
    if not line:
      ser.close()
      break
    print line
    ser.write(line)
    state = '0' # Wait for Arduino before reading next line

ser.close()
myFile.close

下面是Python的输出。代码一次性执行，没有等待Arduino。看起来state = str(ser.read())这一行读取的是某种串口缓冲区中的数据。我猜解决办法是清空这个缓冲区，但我不知道该怎么做。

state 1
239,275;

state 0
state 1
1100,275;

state 0
state 1
300,400;

state 0
state 1
200,400;

state 0
state 1
200,300;

state 0
state 1
[Finished in 0.1s]

如何让通过串口发送的Python数据等待Arduino完成当前任务？

编辑

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