[clug] Raspberry Pi WLAN issues

Stephen Gibson Stephen.Gibson at anu.edu.au
Thu May 29 18:03:56 MDT 2014

Just a follow up on the sensors.

It turns out that the humidity-and-temperature sensor (dht11) uses a 
different interface
(and voltage 3.3V (*)) to the temperature sensor (DS18B20).

The 1-wire DS18B20 interface is neat, connected to one Raspberry Pi GPIO 
pin (and 5V, gnd),
with output via a kernel module:
cat /sys/devices/w1_bus_master1/28-00000559ff29/w1_slave
dd 00 4b 46 7f ff 03 10 23 : crc=23 YES
dd 00 4b 46 7f ff 03 10 23 t=13812

(chilly at my place, but remember this 't' reading is not well calibrated)

Other 1-wire devices may be connected to the same wire.

The dht11 sensor is also connected to a single GPIO pin (and 3.3V, Gnd), 
readings are obtained from a C-code program: Adafruit_DHT.c

Not as neat, as this interface is not a bus.

Just thought I would let you know before you bulk order any of the 


(*) I also abused the dht11, with 5V, having assumed that it was another 
1-wire bus device,
      and simply swapping the wire connections from the DS20, before 
checking the details.
      Its output is now also uncalibrated. Fortunately, these sensors 
are cheap.

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