arduino 串口实时绘图(以mpu9250为例)

兴趣之余,利用晚上的时间,做一些个人兴趣方面的开发. 之前没接触过 arduino, 无意之中买了个开发板做一些小开发, 这里利用python 读取 mpu9250 数据实时绘图.

下位机代码 C++

void Serial_SendDataPython( int16_t *sendData, uint8_t lens )
{
  uint8_t tmpData[] = {};  // tmpData lens >= 2 * lens + 4
  uint8_t *ptrData = tmpData;
  uint8_t dataBytes = lens << ;
  uint8_t dataLens = dataBytes + ;
  uint8_t count = ;
  uint16_t tmpSum = ;

  tmpData[] = 'S';
  while(count < dataBytes) {
//    tmpData[count+1] = Byte8H(sendData[count >> 1]);
//    tmpData[count+2] = Byte8L(sendData[count >> 1]);

    tmpData[count+] = (sendData[count >> ])>>;
    tmpData[count+] = (sendData[count >> ])&0x00ff; ;
    count = count + ;
  }
  for(uint8_t i = ; i < dataBytes; i++)
    tmpSum += tmpData[i+];
  tmpData[dataLens - ] = (uint8_t)(tmpSum & 0x00FF);
  tmpData[dataLens - ] = '\r';
  tmpData[dataLens - ] = '\n';

  do {
    //Serial_SendByte(*ptrData++);
    Serial.write(*ptrData++);
  } while(--dataLens);
}

....................................

IMU_Buf[] = testLostRate++;
MU_Buf[] = ax/;
IMU_Buf[] = ay/;
IMU_Buf[] = az/;
IMU_Buf[] = gx/;
IMU_Buf[] = gy/;
IMU_Buf[] = gz/;
IMU_Buf[] = mx/;
IMU_Buf[] = my/;
IMU_Buf[] = mz/;
Serial_SendDataMATLAB(IMU_Buf, );

.................................................

这里简要说明一下, 发送数据以'S'开头,传感器数据分低8位和高8位数据分别发送,最后以换行符结尾.

 """
 ldr.py
 http://electronut.in/plotting-real-time-data-from-arduino-using-python/
 Display analog data from Arduino using Python (matplotlib)

 Author: Mahesh Venkitachalam
 Website: electronut.in
 """
 import ctypes
 import sys, serial, argparse
 import numpy as np
 from time import sleep
 from collections import deque

 import matplotlib.pyplot as plt
 import matplotlib.animation as animation

 # plot class
 class AnalogPlot:
   # constr
   def __init__(self, strPort, maxLen):
       # open serial port
       self.ser = serial.Serial(strPort, )

       self.ax = deque([0.0]*maxLen)
       self.ay = deque([0.0]*maxLen)
       self.az = deque([0.0]*maxLen)
       self.gx = deque([0.0]*maxLen)
       self.gy = deque([0.0]*maxLen)
       self.gz = deque([0.0]*maxLen)
       self.mx = deque([0.0]*maxLen)
       self.my = deque([0.0]*maxLen)
       self.mz = deque([0.0]*maxLen)
       self.maxLen = maxLen

   # add to buffer
   def addToBuf(self, buf, val):
       if len(buf) < self.maxLen:
           buf.append(val)
       else:
           buf.pop()
           buf.appendleft(val)

   # add data
   def add(self, data):
       assert(len(data) == )
       self.addToBuf(self.ax, data[])
       self.addToBuf(self.ay, data[])
       self.addToBuf(self.az, data[])
       self.addToBuf(self.gx, data[])
       self.addToBuf(self.gy, data[])
       self.addToBuf(self.gz, data[])
       self.addToBuf(self.mx, data[])
       self.addToBuf(self.my, data[])
       self.addToBuf(self.mz, data[])
   # update plot
   def update(self,frameNum,a0,a1,a2,a3,a4,a5,a6,a7,a8):
       try:
           data = self.ser.readline()
           length = len(data)
           if length ==  and ord(data[])== :
             count = (ord(data[])<<)+ord(data[])
             value = (ord(data[])<<)+ord(data[])
             ax = ctypes.c_int16(value).value
             value = (ord(data[])<<)+ord(data[])
             ay = ctypes.c_int16(value).value
             value = (ord(data[])<<)+ord(data[])
             az = ctypes.c_int16(value).value
             value = (ord(data[])<<)+ord(data[])
             gx = ctypes.c_int16(value).value
             value = (ord(data[])<<)+ord(data[])
             gy = ctypes.c_int16(value).value
             value = (ord(data[])<<)+ord(data[])
             gz = ctypes.c_int16(value).value
             value = (ord(data[])<<)+ord(data[])
             mx = ctypes.c_int16(value).value
             value = (ord(data[])<<)+ord(data[])
             my = ctypes.c_int16(value).value
             value = (ord(data[])<<)+ord(data[])
             mz = ctypes.c_int16(value).value

             array = [ax,ay,az,gx,gy,gz,mx,my,mz]
             print array
             self.add(array)
             a0.set_data(range(self.maxLen), self.ax)
             a1.set_data(range(self.maxLen), self.ay)
             a2.set_data(range(self.maxLen), self.az)
             a3.set_data(range(self.maxLen), self.gx)
             a4.set_data(range(self.maxLen), self.gy)
             a5.set_data(range(self.maxLen), self.gz)
             a6.set_data(range(self.maxLen), self.mx)
             a7.set_data(range(self.maxLen), self.my)
             a8.set_data(range(self.maxLen), self.mz)
       except KeyboardInterrupt:
           print('exiting')

       return a0, 

   # clean up
   def close(self):
       # close serial
       self.ser.flush()
       self.ser.close()    

 # main() function
 def main():
   # create parser
   #parser = argparse.ArgumentParser(description="LDR serial")
   # add expected arguments
   #parser.add_argument('--port', dest='port', required=True)

   # parse args
   #args = parser.parse_args()

   strPort = 'COM3'
   #strPort = args.port

   print('reading from serial port %s...' % strPort)

   # plot parameters
   analogPlot = AnalogPlot(strPort, )

   print('plotting data...')

   # set up animation
   fig = plt.figure()
   ax = plt.axes(xlim=(, ), ylim=(-, ))
   a0, = ax.plot([], [])
   a1, = ax.plot([], [])
   a2, = ax.plot([], [])
   a3, = ax.plot([], [])
   a4, = ax.plot([], [])
   a5, = ax.plot([], [])
   a6, = ax.plot([], [])
   a7, = ax.plot([], [])
   a8, = ax.plot([], [])
   anim = animation.FuncAnimation(fig, analogPlot.update,
                                  fargs=(a0,a1,a2,a3,a4,a5,a6,a7,a8),
                                  interval=)

   # show plot
   plt.show()

   # clean up
   analogPlot.close()

   print('exiting.')

 # call main
 if __name__ == '__main__':
   main()

运行结果如下图:

从互联网搜索了一下,可以串口绘图的工具很多,试了一下 SerialChart工具,感觉还不错,界面如下:

下位机数据格式较简单:

interval(两次数据获取时间间隔,可设置为0),ax,ay,az 为int 类型,

Serial.print(interval); //microseconds since last sample, please note that printing more data will increase interval
Serial.print(",");
Serial.print(ax); //Inclination X axis (as measured by accelerometer)
Serial.print(",");
Serial.print(ay); //Inclination X axis (estimated / filtered)
Serial.print(",");
Serial.print(az); //Inclination X axis (estimated / filtered)

Serial.println("");

具体使用方法请参见官方网站: https://en.wikiversity.org/wiki/SerialChart_Tutorial  ,这里有详细说明和配置方法.

总结: 利用 python 读取seria 数据似乎效率不怎么高, 和之前matlab 测试遇到的情况情况类似,容易出现卡顿的情况. 下篇博客我将会介绍数据可视化工具 Processing在这方便的用途和代码.

参考,引用:

http://electronut.in/plotting-real-time-data-from-arduino-using-python/

https://en.wikiversity.org/wiki/SerialChart_Tutorial