Ubuntu 16.04软件中心安装的Arduino IDE报告错误 – avrdude: ser_open(): can't open device "/dev/ttyACM0": Permission denied

最近要使用Arduino开发一个读取电压的装置，新电脑上没有安装Arduino IDE,因此，从Ubuntu 16.04软件中心中搜索找到一个名为arduino-mhall119的软件，如下图所示：
继续阅读Ubuntu 16.04软件中心安装的Arduino IDE报告错误 – avrdude: ser_open(): can't open device "/dev/ttyACM0": Permission denied

树莓派2B启用I2C

树莓派自带I2C控制器，但是默认没有启用，我们需要手工启用，具体操作如下：

I2C is a very commonly used standard designed to allow one chip to talk to another. So, since the Raspberry Pi can talk I2C we can connect it to a variety of I2C capable chips and modules.Here are some of the Adafruit projects that make use of I2C devices and modules:

The I2C bus allows multiple devices to be connected to your Raspberry Pi, each with a unique address, that can often be set by changing jumper settings on the module. It is very useful to be able to see which devices are connected to your Pi as a way of making sure everything is working.

To do this, it is worth running the following commands in the Terminal to install the i2c-tools utility.

$ sudo apt-get install -y python-smbus
$ sudo apt-get install -y i2c-tools

Installing Kernel Support (with Raspi-Config)

继续阅读树莓派2B启用I2C

Python异步通信模块asyncore

Python的asyncore模块提供了以异步的方式写入套接字服务的客户端和服务器的基础结构。

模块主要包括：

asyncore.loop(…) - 用于循环监听网络事件。loop()函数负责检测一个字典，字典中保存dispatcher的实例。

asyncore.dispatcher类 - 一个底层套接字对象的简单封装。这个类有少数由异步循环调用的，用来事件处理的函数。

dispatcher类中的writable()和readable()在检测到一个socket可以写入或者数据到达的时候被调用，并返回一个bool值，决定是否调用handle_read或者handle_write。
asyncore.dispatcher_with_send类 - 一个 dispatcher的子类，添加了简单的缓冲输出能力，对简单的客户端很有用。

import time
import asyncore
import socket
import threading


class EchoHandler(asyncore.dispatcher_with_send):

    def handle_read(self):
        data = self.recv(1024)
        if data:
            self.send(data)

class EchoServer(asyncore.dispatcher):

    def __init__(self, host, port):
        asyncore.dispatcher.__init__(self)
        self.create_socket(socket.AF_INET, socket.SOCK_STREAM)
        self.set_reuse_addr()
        self.bind((host, port))
        self.listen(5)

    def handle_accept(self):
        conn, addr = self.accept()
        print 'Incoming connection from %s' % repr(addr)
        self.handler = EchoHandler(conn)

class EchoClient(asyncore.dispatcher):

    def __init__(self, host, port):
        asyncore.dispatcher.__init__(self)
        self.messages = ['1', '2', '3', '4', '5', '6', '7', '8', '9', '10']
        self.create_socket(socket.AF_INET, socket.SOCK_STREAM)
        self.connect((host, port))

    def handle_connect(self):
        pass

    def handle_close(self):
        self.close()

    def handle_read(self):
        print self.recv(1024)

    def writable(self):
        return (len(self.messages) > 0)

    def handle_write(self):
        if len(self.messages) > 0: 
            self.send(self.messages.pop(0))

class EchoServerThread(threading.Thread):
    def __init__(self):
        threading.Thread.__init__(self)

    def run(self):
        server = EchoServer('localhost', 9999)
        asyncore.loop()

class EchoClientThread(threading.Thread):
    def __init__(self):
        threading.Thread.__init__(self)

    def run(self):
        client = EchoClient('localhost', 9999)
        asyncore.loop()

EchoServerThread().start()
time.sleep(2)
EchoClientThread().start()

参考链接