使用Arduino和Python通过串口连续控制多个伺服系统

Question

我一直在编写这段代码，以便使用Python在Arduino上控制大量的servo。代码可以工作，但我看到了一些关于计时的奇怪行为。在每次更新伺服系统之间，我需要一个睡眠命令。如果我没有插入睡眠，程序将在我第一次运行它时工作，但是如果Python代码被停止，然后我再次尝试通过串行连接到Python，Arduino没有响应。串行端口可能会发生什么情况?我如何防止这种情况发生？

另外，我使用memcpy解析进入Arduino的数据是不是最有效的方式？或者有没有更好或者更标准的方法来做到这一点？

我读过关于使用serialEvent的文章，在这种情况下使用该命令解析串行数据是否有好处？

//ARDUINO CODE
#include <Servo.h> 

int servoPins[] = {9, 10};
//int servoPins[] = {2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38};
//int servoPins[] = {2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34};
const int numServos = sizeof(servoPins)/sizeof(int);
Servo servos[numServos];

char serialData[numServos * 3];
char tempData[3];

void setup() {
  Serial.begin(9600);
  Serial.println("Ready");
  for (int i=0; i < numServos; i++) {
    servos[i].attach(servoPins[i]);
    //servos[i].write(20);
  }
}

void loop() {
  if (Serial.available()) {
    Serial.readBytesUntil('\0', serialData, numServos * 3);

    for (int i=0; i < numServos; i++) {
      memmove(tempData, serialData + i * 3, 3);
      servos[i].write(atoi(tempData));
    }
  }
}


#PYTHON CODE
""" Control n servos on n arduinos over serial

"""

import glob
import platform
import serial
from time import sleep
import sys

'''
Servo
Id number, angle for servo, Arduino port servo is on
For now the port is used as an index, so please number them going from 0-n

'''
class Servo:
    id_num = 0
    angle = 0
    port = 0

    def __init__(self, id_num, angle, port):
        self.id_num = id_num
        self.angle = angle
        self.port = port

'''
ServoDriver
-Stores a list of servos
-Open ports to Arduinos
-Stores a list of those ports
-Creates a map of which servos are on which ports
-Provides a way to update the angle of all servos on all ports
'''
class ServoDriver:
    def __init__(self, servos):
        self.ports = self.open_ports()
        self.servos = servos

    # looks for all devices that have the same name pattern as an Arduino and opens them
    def open_ports(self):
        # find arduinos
        # note: currently this is Mac only
        devices = glob.glob('/dev/tty.usbmodem*')
        print devices

        if len(devices) == 0:
            print "No Arduinos found"
            sys.ext(1)

        ports = []
        for device in devices:
            try:
                # connect to serial port
                ports.append(serial.Serial(device, 9600))
            except:
                print 'Failed to open port'
                sys.ext(1)


        # need a short delay right after serial port is started for the Arduino to initialize
        sleep(2)
        return ports

    # update the angle of all servos on all ports
    def update(self, servos):
        debug = True
        servo_data = []
        for p in self.ports:
            servo_data.append('')
        for servo_update in servos:
            for servo_stored in self.servos:
                if servo_stored.id_num == servo_update.id_num:
                    this_port = servo_stored.port
                    break

            # constrain servo angles to avoid damaging servos
            if servo_update.angle > 135:
                servo_update.angle = 135
            else if servo_update.angle < 45:
                servo_update.angle = 45

            # append angle to the datum for this port
            servo_data[this_port] = servo_data[this_port] + str(servo_update.angle).zfill(3)

        for servo_datum in servo_data:
            # append null byte for arduino to recognize end of data
            servo_datum = servo_datum + "\0"

        # send data to the Arduinos
        for port,servo_datum in zip(self.ports,servo_data):
            port.write(servo_datum)

    def close_ports(self):
        print 'closing ports'
        for port in self.ports:
            port.close()

# generates values for making a servo sweep back and forth
def servo_iter():
    l = []
    #for i in range(0,1):
    l.append(40)
    #for i in range(0,1):
    l.append(80)
    for pos in l:
        yield pos

def servo_iter_2(total):
    for i in range(0,total):
        yield i

if __name__ == "__main__":
    # create a list of servos with mappings to ports
    # if you have the wrong number of servos it acts weird
    #num_servos = 32
    num_servos = 2
    servos = []
    servos.append(Servo(0, 40, 0))
    servos.append(Servo(1, 40, 0))
    '''
    servos.append(Servo(2, 40, 0))
    servos.append(Servo(3, 40, 0))
    servos.append(Servo(4, 40, 0))
    servos.append(Servo(5, 40, 0))
    servos.append(Servo(6, 40, 0))
    servos.append(Servo(7, 40, 0))
    servos.append(Servo(8, 40, 0))
    servos.append(Servo(9, 40, 0))
    servos.append(Servo(10, 40, 0))
    servos.append(Servo(11, 40, 0))
    servos.append(Servo(12, 40, 0))
    servos.append(Servo(13, 40, 0))
    servos.append(Servo(14, 40, 0))
    servos.append(Servo(15, 40, 0))
    servos.append(Servo(16, 40, 0))
    servos.append(Servo(17, 40, 0))
    servos.append(Servo(18, 40, 0))
    servos.append(Servo(19, 40, 0))
    servos.append(Servo(20, 40, 0))
    servos.append(Servo(21, 40, 0))
    servos.append(Servo(22, 40, 0))
    servos.append(Servo(23, 40, 0))
    servos.append(Servo(24, 40, 0))
    servos.append(Servo(25, 40, 0))
    servos.append(Servo(26, 40, 0))
    servos.append(Servo(27, 40, 0))
    servos.append(Servo(28, 40, 0))
    servos.append(Servo(29, 40, 0))
    servos.append(Servo(30, 40, 0))
    servos.append(Servo(31, 40, 0))
    servos.append(Servo(32, 40, 0))
    '''

    #if len(servos) != num_servos:
    #   print 'wrong number of servos'
    #   sys.ext(1)

    # comment out the next two lines if you only have 1 arduino
    #servos.append(Servo(2, 40, 1))
    #servos.append(Servo(3, 40, 1))
    #servos.append(Servo(4, 40, 2))
    #servos.append(Servo(5, 40, 2))

    angles = []
    for i in range(0,len(servos)):
        angles.append(40)

    try:
        # instantiate a driver
        # must happen inside try-finally
        driver = ServoDriver(servos)

        iter1 = False
        if iter1:
            pos = servo_iter()
        else:
            pos = servo_iter_2(len(servos))

        while True:
            try:
                x = pos.next()
            except StopIteration:
                if iter1:
                    pos = servo_iter()
                else:   
                    pos = servo_iter_2(len(servos))
                x = pos.next()
            # create a list of servos with ids and angles to update positions of servos
            if iter1:
                for servo in servos:
                    servo.angle = x
            else:
                for i,servo in zip(angles,servos):
                    servo.angle = i
            # call the driver with the list of servos
            driver.update(servos)
            sleep(0.5)

            for i in range(0, len(servos)):
                if i == x:
                    angles[i] = 80
                else:
                    angles[i] = 40

    # close the serial port on exit, or you will have to unplug the arduinos to connect again
    finally:
        driver.close_ports()

我认为正确的答案是在Arduino上增加一个延迟。

Answer 1

每次通过usb进行串行连接时，Arduino都会重置。如果你想暂时禁用，你可以在接地和复位之间插入一个10微法的电容器。这将防止它自动重置，并且可以很容易地删除程序上载。