Initial Release

gpio/dht_sensor/README.adoc

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+= DHT-11, DHT-22, and AM2302 Sensors
+:xrefstyle: short
+
+The DHT sensors are fairly well known hobbyist sensors for measuring relative humidity and temperature using a capacitive humidity sensor, and a thermistor. While they are slow, one reading every ~2 seconds, they are reliable and good for basic data logging. Communication is based on a custom protocol which uses a single wire for data. 
+
+[NOTE]
+======
+The DHT-11 and DHT-22 sensors are the most common. They use the same protocol but have different characteristics, the DHT-22 has better accuracy, and has a larger sensor range than the DHT-11. The sensor is available from a number of retailers.
+======
+
+== Wiring information
+
+See <<dht-wiring-diagram>> for wiring instructions.
+
+[[dht-wiring-diagram]]
+[pdfwidth=75%]
+.Wiring the DHT-22 temperature sensor to Raspberry Pi Pico, and connecting Pico's UART0 to the Raspberry Pi 4.
+image::pi-and-pico-uart-and-dht-sensor.png[]
+
+NOTE: One of the pins (pin 3) on the DHT sensor will not be connected, it is not used.
+
+You will want to place a 10 kΩ resistor between VCC and the data pin, to act as a medium-strength pull up on the data line. 
+
+Connecting UART0 of Pico to Raspberry Pi as in <<dht-wiring-diagram>> and you should see something similar to <<dht-serial-output-diagram>> in `minicom` when connected to `/dev/serial0` on the Raspberry Pi.
+
+[[dht-serial-output-diagram]]
+[pdfwidth=75%]
+.Serial output over Pico's UART0 in a terminal window.
+image::serial-output.png[]
+
+Connect to `/dev/serial0` by typing,
+
+----
+$ minicom -b 115200 -o -D /dev/serial0
+----
+
+at the command line.
+
+== List of Files
+
+A list of files with descriptions of their function;
+
+CMakeLists.txt:: Make file to incorporate the example in to the examples build tree.
+dht.c:: The example code.
+
+== Bill of Materials
+
+.A list of materials required for the example
+[[dht-22-bom-table]]
+[cols=3]
+|===
+| *Item* | *Quantity* | Details
+| Breadboard | 1 | generic part
+| Raspberry Pi Pico | 1 | http://raspberrypi.org/
+| 10 kΩ resistor | 1 | generic part
+| M/M Jumper wires | 4 | generic part
+| DHT-22 sensor | 1 | generic part
+|===