DHT11/22 Temp and Humidity Sensors

Phishfry

Phishfry

I never realized we have a GPIO driver for DHT11/22 sensor.

gpioths(4)

www.freebsd.org www.freebsd.org

I was having problems compiling the DT Overlay.
The FreeBSD manpage gives this:
Code: 
gpios = <&gpio5 15 GPIO_ACTIVE_HIGH>;
The GPIO_ACTIVE_HIGH setting is faulty.
Code: 
# dtc -O dtb -o rockpro64-gpioths.dtbo -@ rockpro64-gpioths.dts
Error at rockpro64-gpioths.dts:12:33: Expected numbers in array of cells
                gpio = <&pio 1 4 GPIO_ACTIVE_HIGH>;
                                 ^
Error at rockpro64-gpioths.dts:12:33: Expected ; at end of property
                gpio = <&pio 1 4 GPIO_ACTIVE_HIGH>;
                                 ^
Error at rockpro64-gpioths.dts:12:33: Failed to find root node /.
                gpio = <&pio 1 4 GPIO_ACTIVE_HIGH>;
                                 ^
Failed to parse tree.

Simply changing it to 0 does the trick.(Sets the pin high)

/boot/dtb/overlays/rockpro64-gpioths.dts
Code: 
/dts-v1/;
/plugin/;

/ {
    compatible = "rockchip,rk3399";
    fragment@0 {                   
        target-path = "/";
        __overlay__ {
                dht0 {
                compatible = "dht11";
                pinctrl-names = "default";
                gpios = <&gpio1 4 0>;
                status = "okay";
            };
        };
    };
};

Add to /boot/loader.conf :
Code: 
gpioths_load="YES"
fdt_overlays="rockpro64-gpioths.dtbo"


dmesg | grep gpioth
Code: 
gpioths0: <DHT11/DHT22 Temperature and Humidity Sensor> on ofwbus0

sysctl -a | grep gpioths
Code: 
gpioths0: <DHT11/DHT22 Temperature and Humidity Sensor> on ofwbus0
    value:    /boot/kernel/gpioths.ko
    value:    /boot/dtb/overlays/rockpro64-gpioths.dtbo
dev.gpioths.0.fails: 0
dev.gpioths.0.humidity: 70
dev.gpioths.0.temperature: 24.1C
dev.gpioths.0.%parent: ofwbus0
dev.gpioths.0.%pnpinfo: name=dht0 compat=dht11
dev.gpioths.0.%location:
dev.gpioths.0.%driver: gpioths
dev.gpioths.0.%desc: DHT11/DHT22 Temperature and Humidity Sensor
dev.gpioths.%parent:
 
On the DHT11/22, you need a separate data wire for each sensor, right? I'm using a 1-wire temperature/humidity sensor, it's called the WallTH. Problem is (and I think the DHT shares that, as do most inexpensive humidity sensors): If installed outdoors, they will occasionally get condensation on them. And that kills the humidity sensor: if you do it occasionally, they just get inaccurate; if you do it repeatedly, they report insane values. For example, right now it is raining outdoors, and the good weather station reports 94% humidity (which I believe). The two WallTH sensors report 101% and 145%. I've also recently seen them report negative humidity.

I'm still looking for an inexpensive embeddable humidity sensor that survives outdoors, which is easy to wire (no more than 3 wires, and ideally not dedicated wires). Not a high-priority project, just for curiosity.
 
ralphbsz said:
On the DHT11/22, you need a separate data wire for each sensor, right?
Click to expand...
Just doing that now. Adding additional sensors.
Yes it appears each sensor needs a GPIO pin versus One Wire Temp DS1820 which uses a daisy chained OW bus.
The DHT22 is advertised as more accurate version of DHT11.
I found my additional sensors in a tub, AM2302. These should be usable.

It does appear that DHT11/22 offers a 4 pin version which works with I2C.
I do imagine with that you could daisychain. I don't think the driver supports i2c from my source code reading.
/usr/src/sys/dev/gpio/gpioths.c
I really appreciate the exquisitely commented code.
I see this too in the source:
* AM2301: Same as DHT21, but also supports i2c interface.
* AM2302: Same as DHT22, but also supports i2c interface.
Click to expand...
My AM2302 modules are only 3 wire.
I see nothing in the code body about i2c.
 
For a rugged outdoors temperature-only sensor the stainless encapsulated ds1820 probes fit the bill.
www.ebay.com

DS18B20 temperature probe temperature sensor DS1820 Stainless steel Waterproof | eBay

For each lead, we use 30pcs tinning lines, which is different from other DS18B20 sensor wires, it is soft and has better oxidation resistance ability. Size of Stainless steel sheath:6 50mm. Storage temperature range:-55°C to +125°C (-67°F to +257°F).
www.ebay.com
 
Temperature is easy. I use various DS182x sensors, some outdoors (lots of heatshrink and coating, carefully protected from direct rain). Humidity is hard, once condensation happens.
 
We have lift-off:
Code: 
# dmesg | grep gpioth
gpioths0: <DHT11/DHT22 Temperature and Humidity Sensor> on ofwbus0
gpioths1: <DHT11/DHT22 Temperature and Humidity Sensor> on ofwbus0

# sysctl dev.gpioths
dev.gpioths.1.fails: 0
dev.gpioths.1.humidity: 61
dev.gpioths.1.temperature: 22.5C
dev.gpioths.1.%parent: ofwbus0
dev.gpioths.1.%pnpinfo: name=dht0 compat=dht11
dev.gpioths.1.%location:
dev.gpioths.1.%driver: gpioths
dev.gpioths.1.%desc: DHT11/DHT22 Temperature and Humidity Sensor
dev.gpioths.0.fails: 0
dev.gpioths.0.humidity: 67
dev.gpioths.0.temperature: 22.2C
dev.gpioths.0.%parent: ofwbus0
dev.gpioths.0.%pnpinfo: name=dht1 compat=dht11
dev.gpioths.0.%location:
dev.gpioths.0.%driver: gpioths
dev.gpioths.0.%desc: DHT11/DHT22 Temperature and Humidity Sensor
dev.gpioths.%parent:

So my approach in this case was to complicate my overlays with additional details.
Long filenames but descriptive.
rockpro64-gpioths-dht1-pin18.dtbo
I added an incremented dht* name and GPIO header pin number.
That way I can add and remove individual sensors.
The other approach is to jam them all into one overlay.
But when you want to make a change you must recompile.
I like prebuilt dtbo so I can pick and choose.
All it takes that way is add your precompiled binaries as multiple overlays to /boot/loader.conf
Code: 
fdt_overlays="rockpro64-gpioths-dht0-pin16.dtbo,rockpro64-gpioths-dht1-pin18.dtbo,rockpro64-w1-gpio-pin15.dtbo"

Raspberry Pi has that excellent overlay port misc/raspberrypi-userland that offers pre-compiled binary overlays.
Its is a great way to get to work quickly..I try and emulate it on all boards.
 
I had trouble with the HINT based method.
From the handbook:
hint.gpioths._unit_.at
hint.gpioths.pins

The pins setting is missing a required unit number.
hint.gpioths._unit_.pins

gpioths

www.freebsd.org www.freebsd.org
hint.gpioths.pins
A bitmask with a single bit set to indicate which gpio pin on the
gpiobus(4) to use for data communications.
Click to expand...
I am not sure what a bitmask means here.

The pins do not translate properly like they do with One Wire. ie.. Pin1=1 Pin2=2 Pin3=3

Here is my decoder. Enter this value to obtain the desired pin.
Pin 0= 0
Pin 1= 2
Pin 2= 4
Pin 3= 8
Pin 4= 16
Pin 5= 32
Pin 6= 64
Pin 7= 128
Pin 8= 256
Pin 9= 512
Pin 10= 1024
Pin 11= 2048
Pin 12= 4096
Pin 13= 8192
Pin 14= 16384
Pin 15= 32768
Pin 16= 65536
Pin 17= 131672
Pin 18= 262144
Pin 19= 524288
Pin 20= 1048576
Pin 21= 2097152
Pin 22= 4194304
Pin 23= 8388608
Pin 24= 16777216
Pin 25= 33554432
Pin 26= 67108864

So this is what the /boot/loader.conf setting looks like for 6 sensors.
Code: 
gpioths_load="YES"
hint.gpioths.0.at=gpiobus1
hint.gpioths.0.pins=8192
hint.gpioths.1.at=gpiobus1
hint.gpioths.1.pins=262144
hint.gpioths.2.at=gpiobus1
hint.gpioths.2.pins=1048576
hint.gpioths.3.at=gpiobus1
hint.gpioths.3.pins=4194304
hint.gpioths.4.at=gpiobus1
hint.gpioths.4.pins=2097152
hint.gpioths.5.at=gpiobus4
hint.gpioths.5.pins=2097152

Very bizarre the pin number scheme. I took me until pin 9 to recognize the pattern. Much change and try.

This worked on both APU2 and RockPro64.

Code: 
# dmesg | grep gpioths
gpioths0: <DHT11/DHT22 Temperature and Humidity Sensor> at pin 13 on gpiobus1
gpioths1: <DHT11/DHT22 Temperature and Humidity Sensor> at pin 18 on gpiobus1
gpioths2: <DHT11/DHT22 Temperature and Humidity Sensor> at pin 20 on gpiobus1
gpioths3: <DHT11/DHT22 Temperature and Humidity Sensor> at pin 22 on gpiobus1
gpioths4: <DHT11/DHT22 Temperature and Humidity Sensor> at pin 21 on gpiobus1
gpioths5: <DHT11/DHT22 Temperature and Humidity Sensor> at pin 21 on gpiobus4

Code: 
sysctl dev.gpioths | grep temp & sysctl dev.gpioths | grep humidity
dev.gpioths.5.temperature: 23.2C
dev.gpioths.4.temperature: 23.6C
dev.gpioths.3.temperature: 39.2C
dev.gpioths.2.temperature: 24.1C
dev.gpioths.1.temperature: 23.9C
dev.gpioths.0.temperature: 23.6C
dev.gpioths.5.humidity: 55
dev.gpioths.4.humidity: 57
dev.gpioths.3.humidity: 8
dev.gpioths.2.humidity: 55
dev.gpioths.1.humidity: 52
dev.gpioths.0.humidity: 56
 
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