介绍 (Introduction)

When building portable sensors we often want to calibrate and double-check their readings before allowing them to log data remotely. Whilst developing these we can easily SSH into them and write any results to screen. However what happens when we are in a very remote part of the world, with no laptop, wifi or signal?

在制造便携式传感器时，我们经常要校准并仔细检查它们的读数，然后再允许它们远程记录数据。 在开发这些程序时，我们可以轻松地将它们通过SSH SSH并将任何结果写入屏幕。 但是，当我们身处世界的一个偏远地区而没有笔记本电脑，WiFi或信号时，会发生什么呢？

Within this tutorial, we look at exploiting the Bluetooth capabilities of a Raspberry Pi Zero (without WiFi) to transmit the initial set of results to a handheld device of our choosing. In our case, it will be through the use of a mobile phone or android tablet, such that we can compare the sensor and GPS readings.

在本教程中，我们将研究如何利用Raspberry Pi Zero(没有WiFi)的蓝牙功能将初始结果集传输到我们选择的手持设备。 在我们的案例中，将通过使用手机或android平板电脑来进行，以便我们可以比较传感器和GPS读数。

安装与设定 (Installation and Setup)

Before we start there are a couple of changes required for the Bluetooth to work. These are outlined below.

在我们开始之前，需要进行一些更改才能使蓝牙工作。 这些概述如下。

配置设备蓝牙 (Configuring the device Bluetooth)

We begin by changing the configuration of the installed Bluetooth library:

我们首先更改已安装的蓝牙库的配置：

sudo nano /etc/systemd/system/dbus-org.bluez.service

Here we locate the line starting ExecStart , and replace it with the following:

在这里，我们找到以ExecStart开头的行，并将其替换为以下内容：

ExecStart=/usr/lib/bluetooth/bluetoothd --compat --noplugin=sapExecStartPost=/usr/bin/sdptool add SP

Having added the ‘compatibility’ flag, we now have to restart the Bluetooth service on the Pi:

添加了“ compatibility”标志后，我们现在必须在Pi上重新启动蓝牙服务：

sudo systemctl daemon-reload;sudo systemctl restart bluetooth.service;

配对我们的显示器设备 (Pairing our monitor device)

To prevent issues with pairing Bluetooth devices whilst out in the field, it is always a good idea to pre-pair devices — saving their configuration.

为了防止在野外与蓝牙设备配对时出现问题，对设备进行预配对始终是一个好主意-保存其配置。

To do this we use bluetoothctl following the process described in the link below:

为此，我们按照以下链接中所述的过程使用bluetoothctl ：

1. Locate our host MAC address找到我们的主机MAC地址

hcitool scan

This gives results in the format:

这样得出的结果格式如下：

Scanning ...XX:XX:XX:XX:XX:XX device1XX:XX:XX:XX:XX:XX device2

2. select the device we want and copy its address.

2.选择我们想要的设备并复制其地址。

3. execute the following:

3.执行以下操作：

sudo bluetoothctl

4. In the Bluetooth console run the following 3 commands (substituting your copied address):

4.在蓝牙控制台中，运行以下3个命令(替换您的复制地址)：

discoverable on# thenpair XX:XX:XX:XX:XX:XX# and trust XX:XX:XX:XX:XX:XX# where XX corresponds to the address copied from above

When pairing you may be asked to confirm a pin on both devices. trust saves the device address to the trusted list.

配对时，可能会要求您确认两个设备上的引脚。 trust将设备地址保存到可信列表中。

To make a PI discoverable on boot, you can have a look at the code here:

要使PI在启动时可被发现，可以在此处查看代码：

在启动时启用通讯 (Enabling communication on startup)

Finally, we wish to tell the device to watch for incoming Bluetooth connections when it boots. To do this we can add the following file to /etc/rc.local (before the exit command).

最后，我们希望告诉设备在启动时要监视传入的蓝牙连接。 为此，我们可以将以下文件添加到/etc/rc.local (在exit命令之前)。

sudo rfcomm watch hci0 &

Take care to include the ampersand at the end, as otherwise, it will stall the device bootup process. Also if you are reading another device over serial, e.g. a GPS receiver, you may want to use rfcomm1 instead of hci0 (rfcomm0).

请小心在末尾包含＆符，否则，它将使设备启动过程停顿。 同样，如果您正在通过串行方式读取其他设备(例如GPS接收器)，则可能要使用rfcomm1而不是hci0 (rfcomm0) 。

从另一台设备连接到蓝牙串行 (Connecting to the Bluetooth serial from another device)

Depending on what device you are using, the method to read from a serial monitor varies. On an android device, you may take the node/javascript approach (this should work on all operating systems!). For the purpose of this demo, I will describe a method using python to check things are working on a MacBook Pro.

根据所用设备的不同，从串行监视器读取数据的方法也有所不同。 在android设备上，您可以采用node / javascript方法(这在所有操作系统上均适用！)。 出于本演示的目的，我将描述一种使用python检查MacBook Pro上是否工作正常的方法。

确定端口名称 (Determining the port name)

If you have a terminal, the simplest way to do this is to type

如果您有终端，执行此操作的最简单方法是键入

ls /dev/tty.

and hit the tab (autocomplete) button.

并点击标签(自动填充)按钮。

Presuming you have not changed this, this should be your device hostname followed by SerialPort. The default serial port path for a freshly installed raspberry pi should be

假设您尚未更改，则应为设备hostname后跟SerialPort。 新安装的树莓派的默认串行端口路径应为

/dev/tty.raspberrypi-SerialPort

读取收到的数据 (Reading data received)

To read any data received, we can use the python serial library coupled with the following code snippet.

要读取接收到的任何数据，我们可以将python serial库与以下代码段结合使用。

import serialser = serial.Serial('/dev/tty.raspberrypi-SerialPort', timeout=1, baudrate=115000)serial.flushInput();serial.flushOutput()

while True:    out = serial.readline().decode()    if out!='' : print (out)

Note that this is an infinite loop that keeps printing anything it receives. To cancel it when the message ‘exit’ is received we can use:

请注意，这是一个无限循环，不断打印收到的任何内容。 要在收到“退出”消息时取消它，我们可以使用：

if out == 'exit': break

从传感器发送数据 (Sending data from the sensor)

从外壳 (From the shell)

When testing the simplest way to send data is to echo it to /dev/rgcomm0 from the raspberry pi shell. This allows us to manually test communication over the port before writing anything more complicated.

测试发送数据的最简单方法是从/dev/rgcomm0 pi shell将其回显到/dev/rgcomm0 。 这使我们能够在编写更复杂的内容之前手动测试通过端口的通信。

echo "hello!" > /dev/rfcomm0

从python脚本 (From a python script)

If reading data from the raspberry pi and pre-processing it, chances are we will be using python to do the heavy lifting. From here we can treat the rfcomm0 channel as a file and write to it as follows:

如果从树莓派读取数据并对其进行预处理，则很有可能我们将使用python进行繁重的工作。 在这里，我们可以将rfcomm0通道视为一个文件，并按如下所示对其进行写入：

with open(‘/dev/rfcomm0’,’w’,1) as f:     f.write(‘hello from python!’)

结论 (Conclusions)

If we want to quickly check that our sensors are behaving whilst out in the field, we can make use of the Bluetooth capabilities of the Raspberry Pi. This is done by creating a Bluetooth serial port and sending data over it. Such methods are particularly useful if we do not wish to carry bulky laptops, or where a WiFi network is occupied or unavailable.

如果我们想在野外快速检查传感器的运行状况，可以使用Raspberry Pi的蓝牙功能。 这是通过创建蓝牙串行端口并通过其发送数据来完成的。 如果我们不希望携带笨重的笔记本电脑，或者在WiFi网络被占用或不可用的情况下，这种方法特别有用。

More complex tasks such as sending commands to the Raspberry Pi, or even SSHing into it over Bluetooth are also possible but are beyond the scope of this tutorial.

也可以执行更复杂的任务，例如将命令发送到Raspberry Pi，甚至通过蓝牙SSH到Raspberry Pi，但这不在本教程的范围之内。