SerialDevices < Embedded

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---+ Sensors with serial interface

There are 2 sensors with analogue to digital conversion already implemented with the chip:
   * the [[https://datasheets.maximintegrated.com/en/ds/DS18B20.pdf][DS18B20]] digital thermometer from Maxim
   * the [[http://www.micropik.com/PDF/dht11.pdf][DHT11]] digital thermometer and humidity sensor
The DSB20 implements Maxim's 1-wire protocol and our Linux system provides a device driver that periodically reads this chip and displays the temperature value read in the /sys directory.

The DHT11 implements its own private protocol and the user must either write his own device driver or otherwise decode the protocol.

Both PCBs implement an LED in addition to the sensor chip itself: The DHT11 simply shows it the boards is powered while on the !DS18B20 the LED is connected to the data line showing when the chip is accessed.

| <img alt="ds18b20.png" height="557" src="%ATTACHURL%/ds18b20.png" title="ds18b20.png" width="383" /> | <img alt="dht11.png" height="551" src="%ATTACHURL%/dht11.png" title="dht11.png" width="334" /> |
| The !DS18B20 | The DHT11 |
On the !DS18B20 the S pin corresponds to the data line. While in principle the chip can be powered by pulling up the data line, in which case the middle pin is unused, we provide Vcc power to the chip through the middle pin.

-- %USERSIG{UliRaich - 2017-02-04}%

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Topic attachments
I	Attachment	History	Action	Size	Date	Who	Comment
png	dht11.png	r1	manage	597.9 K	2017-02-04 - 13:35	UnknownUser
png	ds18b20.png	r1	manage	699.8 K	2017-02-04 - 13:35	UnknownUser

Topic revision: r1 - 2017-02-04 - uli