# Wireless Lab 3

###### tags: `Wireless`

## :star: 實驗結果
1. 請讀取溫溼度感應器的資料，並使用OTAA送出資料，分別截圖`join_ttn.py`,`send_ttn.py`的結果
2. 傳輸資料後用MQTT查看，並用base64解密截圖。
3. **以組為單位(一個人上傳即可)**，將這些截圖結果貼成一個word檔案，命名為`wireless-lab3-groupxx.docx`，並上傳到LMS作業區。

## [DHT22](https://kingfff.blogspot.com/2018/05/raspberry-pi-3-model-bdht22.html)
1. 首先要將溫溼度感應器晶片插在Raspberry Pi上
* sensor有三個腳位，請對照GPIO腳位圖
* `+` : 接3.3V (#1)
* `out` : 接GPIO4 (#7)
* `-` : GND (#9)


2. 之後在Raspberry Pi上安裝DHT所需要的Library

    $ sudo pip3 install Adafruit_DHT

3. 使用下載[Adafruit_Python_DHT](https://github.com/adafruit/Adafruit_Python_DHT)程式碼

    $ git clone https://github.com/adafruit/Adafruit_Python_DHT

4. 測試

    $ cd Adafruit_Python_DHT/examples
    $ python3 AdafruitDHT.py 22 4

* 參數一：22，表示使用Adafruit_DHT.DHT22
* 參數二：4 ，表示data的接腳是接在GPIO4


5. 請想辦法與Lab2(OTAA)結合，可以查看Adafruit_DHT.py的程式，把一部分的程式移植到Lab2的程式裡

import sys

import Adafruit_DHT


# Parse command line parameters.
sensor_args = { '11': Adafruit_DHT.DHT11,
                '22': Adafruit_DHT.DHT22,
                '2302': Adafruit_DHT.AM2302 }
if len(sys.argv) == 3 and sys.argv[1] in sensor_args:
    sensor = sensor_args[sys.argv[1]]
    pin = sys.argv[2]
else:
    print('Usage: sudo ./Adafruit_DHT.py [11|22|2302] <GPIO pin number>')
    print('Example: sudo ./Adafruit_DHT.py 2302 4 - Read from an AM2302 connected to GPIO pin #4')
    sys.exit(1)

# Try to grab a sensor reading.  Use the read_retry method which will retry up
# to 15 times to get a sensor reading (waiting 2 seconds between each retry).
# 主要偵測的function
humidity, temperature = Adafruit_DHT.read_retry(sensor, pin)

# Un-comment the line below to convert the temperature to Fahrenheit.
# temperature = temperature * 9/5.0 + 32

# Note that sometimes you won't get a reading and
# the results will be null (because Linux can't
# guarantee the timing of calls to read the sensor).
# If this happens try again!
if humidity is not None and temperature is not None:
    print('Temp={0:0.1f}*  Humidity={1:0.1f}%'.format(temperature, humidity))
else:
    print('Failed to get reading. Try again!')
    sys.exit(1)

6. 可能的結果