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Measure temperature and humidity with Ameba

DHT11 is a temperature and humidity sensor which operates at voltage 3.3V~5V.

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DHT11 is a temperature and humidity sensor which operates at voltage 3.3V~5V. At room temperature, the measurable range of the humidity is 20% ~ 90%RH with ±5%RH precision, the measurable range of the temperature is 0 ~ 50℃ with ±2℃ precision. Another choice of temperature and humidity sensor is DHT22 sensor, which has better precision. Its measurable range of the humidity is 0%~100%RH with ±5%RH precision, the measurable range of the temperature is -40~125 ℃ with ±0.2℃ precision.

Ameba RTL8722DM is a low-power dual-band WLAN and Bluetooth Low Energy SoC by Realtek. The RTL8722DM also include memory for Wi-Fi protocol functions and application making it simple for anyone to develop various kind of IoT applications. At the same time it has a wide range of peripheral interfaces. With all these interfaces, it can connect to most of the electronics components like LEDs, temperature and humidity sensors, and so on.

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If you need additional technical documents or the source code for this project. Please visit the official websites and join the Facebook group and forum.

  • 1 × RTL8722DM_MINI Microcontroller
  • 1 × DHT11 or DHT22 or DHT21 sensor

  • 1
    Setup

    There are 4 pins on the sensor:

    Since one of the 4 pins has no function, there are temperature/humidity sensors with only 3 pins on the market:

    DHT is normally in the sleeping mode. To get the temperature/humidity data, please follow the steps:

    1. Awake DHT: Ameba toggles low its DATA pin of GPIO. Now the DATA pin of GPIO serves as digital out to Ameba.
    2. DHT response: DHT also toggle low its DATA pin of GPIO. Now the DATA pin of GPIO serves as digital in for Ameba.
    3. DHT sends data: DHT sends out the temperature/humidity data (which has size 5 bytes) in a bit by bit manner. To represent each bit, DHT first pull low the DATA GPIO pin for a while and then pull high. If the duration of high is smaller than low, it stands for bit 0. Otherwise it stands for bit 1.

    Follow the wiring diagram below:

  • 2
    Final Result

    Open the sample code in “Files” -> “Examples” -> “AmebaGPIO” -> “DHT_Tester”. Compile and upload to Ameba, then press the reset button. The result would be shown on the Serial Monitor.

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