Ameba Arduino: [RTL8722CSM] [RTL8722DM] [RTL8722DM MINI] GPIO - Measuring The Temperature And Humidity

Preparation
  • AmebaD [RTL8722DM / RTL8722CSM / RTL8722DM MINI] x 1
  • DHT11 or DHT22 or DHT21
Example
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. There are 4 pins on the sensor: 1 Since one of the 4 pins has no function, there are temperature/humidity sensors with only 3 pins on the market: 2 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.
3 RTL8722DM / RTL8722CSM wiring diagram: 4 RTL8722DM MINI wiring diagram: 4 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. 5
Code Reference
Use dht.readHumidity() read the humidity value, and use dht.readTemperature() to read the temperature value.
Every time we read the temperature/humidity data, Ameba uses the buffered temperature/humidity data unless it found the data has expired (i.e., has not been updated for over 2 seconds). If the data is expired, Ameba issues a request to DHT to read the latest data.
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Please confirm that QQ communication software is installed