Difference between revisions of "Matrix - Temperature and Humidity Sensor"

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==Introduction==
 
==Introduction==
 
[[File:TemperatureAndHumiditySensor01.png|thumb|Temperature and Humidity Sensor]]
 
[[File:TemperatureAndHumiditySensor01.png|thumb|Temperature and Humidity Sensor]]
−
This module utilizes the DHT11 temperature and humidity sensor. The DHT11 sensor's relative humidity range is 20%-80% ±5% and its temperature range is 0℃-50℃ ±2℃. DHT11 uses a single bus communication which needs only one data line. DATA is used for communication and synchronization between the microprocessor and DHT11. Its data format consists of the 8bit humidity integer data and 8bit the Humidity decimal data, and 8 bit temperature integer data and 8bit fractional temperature data and 8 bit parity bit. Its application of a dedicated digital modules collection technology and the temperature and humidity sensing technology, to ensure that the product has high reliability, excellent long-term stability, low cost and long distance (up to 20 meters) signal transmission. We simplified the DHT11's 4-pin to 3-pin.
+
* The Matrix-Temperature_and_Humidity_Sensor module is used to detect temperature and humidity.
 +
* It utilizes the DHT11 temperature and humidity sensor. Its humidity range is 20% - 80% and the accuracy is 5%. Its temperature range is 0℃ - 50℃ and the accuracy is ±2℃.
  
−
==特性==
+
==Features==
−
* 测量范围 湿度20-80%RH， 温度0~50℃
+
* Humidity range: 20 - 80%RH, Temperature range 0 ~ 50℃
−
* 测量精度 湿度+-5%RH， 温度+-2℃
+
* Accuracy of humidity: +-5%RH, accuracy of temperature: +-2℃
−
* 一线协议
+
* One wire communication
−
* 2.54mm排针接口，接线方便，通用性强
+
* 2.54 mm spacing pin
 +
* PCB dimension (mm): 16 x 32
 +
[[File:dht11pcb.png|frameless|400px|温湿度传感器PCB]]
  
−
==使用方法==
+
Pin Description: <br>
−
===连接===
+
{| class="wikitable"
−
*连接到Tiny4412 SDK (1506)
+
|-
−
::GND针脚:   接地
+
|Pin || Description
−
::VCC:  接5V
+
|-
−
::S针脚：接GPIO PIN1, 必须使用中断引脚，可用引脚(1、2、3、4、9、10)
+
|S   || GPIO
 +
|-
 +
|V    || Supply Voltage 5V
 +
|-
 +
|G    || Ground
 +
|}
  
−
===Linux下的C示例===
+
==Basic Device Operation==
 +
The DHT11 module uses a simplified single-bus serial communication. DATA controls communication and synchronization between the microprocessor and DHT11. A data transfer takes 4ms. The data format contains an integer part and a decimal part. The basic operation is as follows:
 +
* a transmission of 40 data, the high first-out
 +
* data format: 8bit humidity integer data + 8bit the Humidity decimal data <br>
 +
* 8bit temperature integer data + 8bit fractional temperature data <br>
 +
* 8 bit parity bit <br>
 +
* If a transmission is successful the “8bit humidity integer data + 8bit humidity decimal data +8 bit temperature integer data + 8bit temperature fractional data” 8bit checksum is equal to the results of the last eight. <br>
 +
* After the user host (MCU) sends a signal DHT11 is converted from low-power mode to high-speed mode, until the host begins to signal the end. Then DHT11 sends a response signal to send 40bit data, and trigger a letter collection. If DHT11 doesn't receive a signal from the host it will not begin a letter collection. After the letter collection is done DHT11 will turn to low power mode.
 +
 
 +
 
 +
==Applications==
 +
===Connect to NanoPi M1===
 +
Refer to the following connection diagram to connect the module to the NanoPi M1:<br>
 +
[[File:Matrix-Temperature_and_Humidity_Sensor_nanopi_m1.jpg|frameless|600px|Matrix-Temperature_and_Humidity_Sensor_nanopi_m1]]
 +
 
 +
Connection Details:
 +
{| class="wikitable"
 +
|-
 +
|Matrix-Temperature_and_Humidity_Sensor || NanoPi M1
 +
|-
 +
|S    || Pin7
 +
|-
 +
|V    || Pin4
 +
|-
 +
|G    || Pin6
 +
|}
 +
 
 +
===Connect to NanoPi 2===
 +
Refer to the following connection diagram to connect the module to the NanoPi 2:<br>
 +
[[File:Matrix-Temperature_and_Humidity_Sensor_nanopi_2.jpg|frameless|600px|Matrix-Temperature_and_Humidity_Sensor_nanopi_2]]
 +
 
 +
Connection Details:
 +
{| class="wikitable"
 +
|-
 +
|Matrix-Temperature_and_Humidity_Sensor || NanoPi 2
 +
|-
 +
|S    || Pin7
 +
|-
 +
|V    || Pin4
 +
|-
 +
|G    || Pin6
 +
|}
 +
 
 +
===Connect to NanoPi M2 / NanoPi 2 Fire===
 +
Refer to the following connection diagram to connect the module to the NanoPi M2/ NanoPi 2 Fire:<br>
 +
[[File:Matrix-Temperature_and_Humidity_Sensor_nanopi_m2.jpg|frameless|600px|Matrix-Temperature_and_Humidity_Sensor_nanopi_m2]]
 +
 
 +
Connection Details:
 +
{| class="wikitable"
 +
|-
 +
|Matrix-Temperature_and_Humidity_Sensor || NanoPi M2
 +
|-
 +
|S    || Pin7
 +
|-
 +
|V    || Pin4
 +
|-
 +
|G    || Pin6
 +
|}
 +
 
 +
===Connect to NanoPC-T2===
 +
Refer to the following connection diagram to connect the module to the NanoPC-T2:<br>
 +
[[File:Matrix-Temperature_and_Humidity_Sensor_NanoPC-T2.jpg|frameless|600px|Matrix-Temperature_and_Humidity_Sensor_NanoPC-T2]]
 +
 
 +
Connection Details:
 +
{| class="wikitable"
 +
|-
 +
|Matrix-Temperature_and_Humidity_Sensor || NanoPC-T2
 +
|-
 +
|S    || Pin15
 +
|-
 +
|V    || Pin29
 +
|-
 +
|G    || Pin30
 +
|}
 +
 
 +
==Compile & Run Test Program==
 +
Boot your ARM board with Debian and copy the matrix code:
 +
<syntaxhighlight lang="bash">
 +
$ apt-get update && apt-get install git
 +
$ git clone https://github.com/friendlyarm/matrix.git
 +
</syntaxhighlight>
 +
If your cloning is done successfully a "matrix" directory will be generated.
 +
 
 +
Compile and install Matrix:
 +
<syntaxhighlight lang="bash">
 +
$ cd matrix
 +
$ make && make install
 +
</syntaxhighlight>
 +
 
 +
Run test program:
 +
<syntaxhighlight lang="bash">
 +
$ matrix-temp_humidity
 +
</syntaxhighlight>
 +
Note: this module is not plug and play therefore before running the module please make sure it is connected to an ARM board.<br>
 +
Here is what you should observe:<br>
 +
<syntaxhighlight lang="bash">
 +
The humidity is 35000
 +
The temperature is 26000
 +
</syntaxhighlight>
 +
The module successfully read the environment's humidity and temperature values.
 +
 
 +
==Code Sample==
 +
This Matrix code sample can work with all the ARM boards mentioned in this module's wiki. The name of this code sample is "matrix-temperature_and_humidity_sensor". Here is its source code:
 +
<syntaxhighlight lang="c">
 +
int main(int argc, char ** argv)
 +
{
 +
    int ret = -1;
 +
    int dhtTemp=0, dhtHdty=0, board;
 +
    char modStr[BUF_SIZE];
 +
    int pin = GPIO_PIN(7);
 +
 
 +
    if ((board = boardInit()) < 0) {
 +
        printf("Fail to init board\n");
 +
        return -1;
 +
    }   
 +
    if (board == BOARD_NANOPI_T2)
 +
        pin = GPIO_PIN(15);
 +
   
 +
    sprintf(modStr, "modprobe %s gpio=%d", DRIVER_MODULE, pintoGPIO(pin));
 +
    system(modStr);
 +
    if ((ret = dht11Read(DHT_HUMIDITY, &dhtHdty)) != -1) {
 +
        printf("The humidity is %d\n", dhtHdty);
 +
    } else {
 +
        printf("Faided to get humidity\n");
 +
    }
 +
    if ((ret = dht11Read(DHT_TEMP, &dhtTemp)) != -1) {
 +
        printf("The temperature is %d\n", dhtTemp);
 +
    } else {
 +
        printf("Faided to get temperature\n");
 +
    }
 +
    system("rmmod "DRIVER_MODULE);
 +
    return ret;
 +
}
 +
</syntaxhighlight>
 +
For more details about this APIs called in this code sample refer to [[Matrix API reference manual]] <br>
 +
 
 +
<!---
 +
==Download Matrix Source Code==
 +
All the matrix modules' code samples are open source. They are maintained on GitHub - https://github.com/friendlyarm/matrix.git <br>
 +
Each branch in this hub contains the matrix modules' code samples for a board that the matrix modules can work with.<br>
 +
* The nanopi branch contains the matrix modules' code samples for the NanoPi
 +
* The nanopi 2 branch contains the matrix modules' code samples for the NanoPi 2
 +
* The tiny4412 branch contains the matrix modules' code samples for the Tiny4412
 +
* The raspberrypi branch contains the matrix modules' code samples for the RaspberryPi
 +
 
 +
Please follow the steps below to get the source code:<br>
 +
Install the git utility on a PC running Ubuntu14.04
 +
<syntaxhighlight lang="bash">
 +
$ sudo apt-get install git
 +
</syntaxhighlight>
 +
 
 +
Clone the matrix code from GitHub
 +
<syntaxhighlight lang="bash">
 +
$ git clone https://github.com/friendlyarm/matrix.git
 +
</syntaxhighlight>
 +
If this is successful a "matrix" directory will be generated, which will contain all the matrix modules' code samples.
 +
 
 +
==Connect to NanoPi 2==
 +
===Hardware Connection===
 +
Please refer to the following connection diagram to connect the Matrix-Temperature_and_Humidity_Sensor to the NanoPi 2:<br>
 +
[[File:Matrix-Temperature_and_Humidity_Sensor_nanopi_2.jpg|frameless|600px|Matrix-Temperature_and_Humidity_Sensor_nanopi_2]]
 +
 
 +
Connection Details:
 +
{| class="wikitable"
 +
|-
 +
|Matrix-Temperature_and_Humidity_Sensor || NanoPi 2
 +
|-
 +
|S  || Pin7
 +
|-
 +
|V  || Pin4
 +
|-
 +
|G  || Pin6
 +
|}
 +
 
 +
===Compile Test Program===
 +
Please login the matrix hub and enter the nanopi2 branch
 +
<syntaxhighlight lang="bash">
 +
$ cd matrix
 +
$ git checkout nanopi2
 +
</syntaxhighlight>
 +
 
 +
Compile the matrix code
 +
<syntaxhighlight lang="bash">
 +
$ make CROSS_COMPILE=arm-linux- clean
 +
$ make CROSS_COMPILE=arm-linux-
 +
$ make CROSS_COMPILE=arm-linux- install
 +
</syntaxhighlight>
 +
Note: please make sure to install the cross compiler "arm-linux-gcc-4.9.3" on your PC, which is used to compile files for the NanoPi 2.<br>
 +
Generated library files are under the "install/lib" directory. The test program is under the "install/usr/bin" directory.<br>
 +
The modules are under the "modules" directory. The driver's source code is in github: https://github.com/friendlyarm/linux-3.4.y.git <br>
 +
 
 +
===Run Test Program===
 +
Please insert a TF card which is flashed with Debian to a Linux host and mount its boot and rootfs sections.<br>
 +
We assume the rootfs is mounted to /media/rootfs then please run the following commands to copy the module, library and test program to the card.<br>
 +
<syntaxhighlight lang="bash">
 +
$ cp modules /media/rootfs/ -r
 +
$ cp install/lib/* /media/rootfs/lib/ -d
 +
$ cp install/usr/bin/* /media/rootfs/usr/bin/
 +
</syntaxhighlight>
 +
 
 +
Insert this TF card to your NanoPi 2, power on and run the following commands to load the driver.<br>
 +
<syntaxhighlight lang="bash">
 +
$ cd /modules
 +
$ insmod dht11.ko
 +
</syntaxhighlight>
 +
 
 +
Start the matrix-temp_humidity program.<br>
 +
<syntaxhighlight lang="bash">
 +
$ matrix-temp_humidity
 +
</syntaxhighlight>
 +
 
 +
Here is what you expect to observe:<br>
 +
[[File:matrix-temp_humidity_result.png|frameless|600px|matrix-temp_humidity_result]] <br>
 +
 
 +
===Code Sample===
 +
<syntaxhighlight lang="c">
 +
int main(int argc, char ** argv)
 +
{
 +
    int ret = -1;
 +
    int dhtTemp = 0;
 +
    int dhtHdty = 0;
 +
 
 +
    if ((ret = dht11Read(DHT_HUMIDITY, &dhtHdty)) != -1) {
 +
        printf("Get humidity : %d\n", dhtHdty);
 +
    } else {
 +
        printf("Faided to get humidity\n");
 +
    }
 +
 
 +
    if ((ret = dht11Read(DHT_TEMP, &dhtTemp)) != -1) {
 +
        printf("Get temperature : %d\n", dhtTemp);
 +
    } else {
 +
        printf("Faided to get temperature\n");
 +
    }
 +
 
 +
    return ret;
 +
}
 +
</syntaxhighlight>
 +
 
 +
==Connect to NanoPi==
 +
===Preparations===
 +
Please install a Debian on a NanoPi and an appropriate cross compiler on a PC. Please refer to wiki:[[NanoPi/zh|NanoPi]] <br>
 +
Compile a NanoPi kernel. Note: please use the kernel's source code from the nanopi-v4.1.y-matrix branch.<br>
 +
<syntaxhighlight lang="bash">
 +
$ git clone https://github.com/friendlyarm/linux-4.x.y.git
 +
$ cd linux-4.x.y
 +
$ git checkout nanopi-v4.1.y-matrix
 +
$ make nanopi_defconfig
 +
$ touch .scmversion
 +
$ make
 +
</syntaxhighlight>
 +
 
 +
===Hardware Connection===
 +
Please refer to the following connection diagram to connect the Matrix-Temperature_and_Humidity_Sensor to the NanoPi <br>
 +
[[File:matrix-temperature_and_humidity_sensor_nanopi.jpg|frameless|600px|matrix-temperature_and_humidity_sensor_nanopi]]
 +
<br>
 +
Connection Details:
 +
{| class="wikitable"
 +
|-
 +
|Matrix-Temperature_and_Humidity_Sensor || NanoPi
 +
|-
 +
|S  || Pin7
 +
|-
 +
|V    || Pin4
 +
|-
 +
|G  || Pin6
 +
|}
 +
 
 +
===Compile Test Program===
 +
Please login the matrix hub and enter the nanopi branch
 +
<syntaxhighlight lang="bash">
 +
$ cd matrix
 +
$ git checkout nanopi
 +
</syntaxhighlight>
 +
 
 +
Compile the matrix code
 +
<syntaxhighlight lang="bash">
 +
$ make CROSS_COMPILE=arm-linux- clean
 +
$ make CROSS_COMPILE=arm-linux-
 +
$ make CROSS_COMPILE=arm-linux- install
 +
</syntaxhighlight>
 +
Note: please make sure to install the cross compiler "arm-linux-gcc-4.4.3" on your PC, which is used to compile files for the NanoPi-Debian.<br>
 +
Generated library files are under the "install/lib" directory. Applications are under the "install/usr/bin" directory. The test program for the "Matrix-Temperature_and_Humidity_Sensor" module is "matrix-temp_humidity".<br>
 +
 
 +
===Run Test Program===
 +
Please copy the library files and test program to the NanoPi
 +
<syntaxhighlight lang="bash">
 +
$ cp install/usr/usr/bin/* nanopi_rootfs/usr/usr/bin/
 +
$ cp install/lib/* nanopi_rootfs/lib/ -d
 +
</syntaxhighlight>
 +
 
 +
Power on the NanoPi and run the following command in Debian's terminal <br>
 +
Note: this module is not plug and play therefore before running the module please make sure it is connected to a NanoPi.
 +
<syntaxhighlight lang="bash">
 +
$ matrix-temp_humidity
 +
</syntaxhighlight>
 +
 
 +
===Code Sample===
 +
<syntaxhighlight lang="c">
 +
int main(int argc, char ** argv)
 +
{
 +
    int ret = -1;
 +
    int dhtTemp = 0;
 +
    int dhtHdty = 0;
 +
    int devFD = -1;
 +
    int pin = GPIO_PIN1;
 +
 
 +
    if (argc == 2) {
 +
        parseCmd(argc, argv, &pin);
 +
    } else {
 +
        printf("Using default pin GPIO_PIN1\n");
 +
    }
 +
    if ((devFD = dht11Init(pin)) == -1) {
 +
        printf("Fail to init dht11\n");
 +
        return -1;
 +
    }
 +
 
 +
    if ((ret = dht11Read(DHT_HUMIDITY, &dhtHdty)) != -1) {
 +
        printf("Get humidity : %d\n", dhtHdty);
 +
    } else {
 +
        printf("Faided to get humidity\n");
 +
    }
 +
 
 +
    if ((ret = dht11Read(DHT_TEMP, &dhtTemp)) != -1) {
 +
        printf("Get temperature : %d\n", dhtTemp);
 +
    } else {
 +
        printf("Faided to get temperature\n");
 +
    }
 +
 
 +
    dht11DeInit(devFD);
 +
    return ret;
 +
}
 +
</syntaxhighlight>
 +
 
 +
==Connect to Tiny4412==
 +
===Preparations===
 +
Please refer to the Tiny4412's user's manual to install a UbuntuCore on the Tiny4412 and install an appropriate cross compiler on a PC.<br>
 +
Note: only the Tiny4412SDK-1506 carrier board can work with this module.
 +
 
 +
===Hardware Connection===
 +
Please refer to the following diagram to connect the Matrix-Temperature_and_Humidity_Sensor to the Tiny4412 <br>
 +
[[File:matrix-temperature_and_humidity_sensor_tiny4412.jpg|frameless|600px|matrix-temperature_and_humidity_sensor_tiny4412]]
 +
 
 +
Connection Details:
 +
{| class="wikitable"
 +
|-
 +
|Matrix-Temperature_and_Humidity_Sensor || Tiny4412
 +
|-
 +
|S  || GPIO1 S
 +
|-
 +
|V    || GPIO1 5V
 +
|-
 +
|G  || GPIO1 GND
 +
|}
 +
 
 +
===Compile Test Program===
 +
Please login the Matrix hub and enter the matrix-tiny4412 branch
 +
<syntaxhighlight lang="bash">
 +
$ cd matrix
 +
$ git checkout tiny4412
 +
</syntaxhighlight>
 +
 
 +
Compile the matrix code
 +
<syntaxhighlight lang="bash">
 +
$ make CROSS_COMPILE=arm-linux-gnueabihf- clean
 +
$ make CROSS_COMPILE=arm-linux-gnueabihf-
 +
$ make CROSS_COMPILE=arm-linux-gnueabihf- install
 +
</syntaxhighlight>
 +
Note: please make sure to install the cross compiler "arm-linux-gnueabihf-gcc-4.7.3" on your PC, which is used to compile files for the Tiny4412-UbuntuCore.<br>
 +
Generated library files are under the "install/lib" directory. Applications are under the "install/usr/bin" directory. The test program for the "Matrix-Temperature_and_Humidity_Sensor" module is "matrix-temp_humidity".
 +
 
 +
===Run Test Program===
 +
Please copy the library files and test program to the Tiny4412
 +
<syntaxhighlight lang="bash">
 +
$ cp install/usr/usr/bin/* tiny4412_rootfs/usr/usr/bin/
 +
$ cp install/lib/* tiny4412_rootfs/lib/ -d
 +
</syntaxhighlight>
 +
 
 +
Power on the Tiny4412 and run the following command in UbuntuCore's terminal <br>
 +
Note: this module is not plug and play therefore before running the module please make sure it is connected to a Tiny4412.
 +
<syntaxhighlight lang="bash">
 +
$ matrix-temp_humidity
 +
</syntaxhighlight>
 +
 
 +
===Code Sample===
 +
<syntaxhighlight lang="c">
 +
int main(int argc, char ** argv)
 +
{
 +
    int ret = -1;
 +
    int dhtTemp = 0;
 +
    int dhtHdty = 0;
 +
    int devFD = -1;
 +
    int pin = GPIO_PIN1;
 +
 
 +
    if (argc == 2) {
 +
        parseCmd(argc, argv, &pin);
 +
    } else {
 +
        printf("Using default pin GPIO_PIN1\n");
 +
    }
 +
    if ((devFD = dht11Init(pin)) == -1) {
 +
        printf("Fail to init dht11\n");
 +
        return -1;
 +
    }
 +
 
 +
    if ((ret = dht11Read(DHT_HUMIDITY, &dhtHdty)) != -1) {
 +
        printf("Get humidity : %d\n", dhtHdty);
 +
    } else {
 +
        printf("Faided to get humidity\n");
 +
    }
 +
 
 +
    if ((ret = dht11Read(DHT_TEMP, &dhtTemp)) != -1) {
 +
        printf("Get temperature : %d\n", dhtTemp);
 +
    } else {
 +
        printf("Faided to get temperature\n");
 +
    }
 +
 
 +
    dht11DeInit(devFD);
 +
    return ret;
 +
}
 +
</syntaxhighlight>
 +
 
 +
==Connect to RaspberryPi==
 +
 
 +
==Connect to Arduino==
 +
--->
 +
 
 +
==Resources==
 +
[http://akizukidenshi.com/download/ds/aosong/DHT11.pdf DHT11.pdf]
 +
 
 +
==Update Log==
 +
===Feb-23-2016===
 +
* Added the description for "NanoPi 2 branch" in Section 4
 +
* Added Section 5: Connect to NanoPi 2
 +
===June-24-2016===
 +
* Re-organized and simplified wiki
 +
 
 +
 
 +
<!--
 +
==Introduction==
 +
[[File:TemperatureAndHumiditySensor01.png|thumb|Temperature and Humidity Sensor]]
 +
This module utilizes the DHT11 temperature and humidity sensor. The DHT11 sensor's relative humidity range is 20%-80% ±5% and its temperature range is 0℃-50℃ ±2℃. DHT11 uses a single bus communication which needs only one data line. Its DATA line is used for communication and synchronization between the microprocessor and DHT11. Its data format consists of the 8bit humidity integer data and 8bit the Humidity decimal data, and 8 bit temperature integer data and 8bit fractional temperature data and 8 bit parity bit. Its application of a dedicated digital modules collection technology and the temperature and humidity sensing technology, to ensure that the product has high reliability, excellent long-term stability, low cost and long distance (up to 20 meters) signal transmission. We simplified the DHT11's 4-pin to 3-pin.
 +
 
 +
==Features==
 +
* Humidity range: 20-80%RH, temperature range: 0~50℃
 +
* Humidity accuracy:±5%RH, temperature accuracy: ±2℃
 +
* Single bus (I/O) communication
 +
* 2.54 mm spacing pin
 +
 
 +
==How To==
 +
===Connection===
 +
*Connect to Tiny4412 SDK (1506)
 +
::GND:  Ground
 +
::VCC:  5V
 +
::S:    GPIO PIN1, this pin has to be connected to an interrupt pin.
 +
 
 +
===Code Sample in C Under Linux===
 
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<syntaxhighlight lang="c">
 
#include <stdio.h>
 
#include <stdio.h>
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===编译并运行示例===
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===Compile and Run===
 
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git clone http://github.com/friendlyarm/fa-hardware.git
 
git clone http://github.com/friendlyarm/fa-hardware.git
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make
 
make
 
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将编译生成的dht11通过ftp上传到开发板上运行即可测试。
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Copy your compiled bin to your board and you are ready to go.
  
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==相关资料==
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==Resources==
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Latest revision as of 15:50, 24 June 2016

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1 Introduction

Temperature and Humidity Sensor
  • The Matrix-Temperature_and_Humidity_Sensor module is used to detect temperature and humidity.
  • It utilizes the DHT11 temperature and humidity sensor. Its humidity range is 20% - 80% and the accuracy is 5%. Its temperature range is 0℃ - 50℃ and the accuracy is ±2℃.

2 Features

  • Humidity range: 20 - 80%RH, Temperature range 0 ~ 50℃
  • Accuracy of humidity: +-5%RH, accuracy of temperature: +-2℃
  • One wire communication
  • 2.54 mm spacing pin
  • PCB dimension (mm): 16 x 32

温湿度传感器PCB

Pin Description:

Pin Description
S GPIO
V Supply Voltage 5V
G Ground

3 Basic Device Operation

The DHT11 module uses a simplified single-bus serial communication. DATA controls communication and synchronization between the microprocessor and DHT11. A data transfer takes 4ms. The data format contains an integer part and a decimal part. The basic operation is as follows:

  • a transmission of 40 data, the high first-out
  • data format: 8bit humidity integer data + 8bit the Humidity decimal data
  • 8bit temperature integer data + 8bit fractional temperature data
  • 8 bit parity bit
  • If a transmission is successful the “8bit humidity integer data + 8bit humidity decimal data +8 bit temperature integer data + 8bit temperature fractional data” 8bit checksum is equal to the results of the last eight.
  • After the user host (MCU) sends a signal DHT11 is converted from low-power mode to high-speed mode, until the host begins to signal the end. Then DHT11 sends a response signal to send 40bit data, and trigger a letter collection. If DHT11 doesn't receive a signal from the host it will not begin a letter collection. After the letter collection is done DHT11 will turn to low power mode.


4 Applications

4.1 Connect to NanoPi M1

Refer to the following connection diagram to connect the module to the NanoPi M1:
Matrix-Temperature_and_Humidity_Sensor_nanopi_m1

Connection Details:

Matrix-Temperature_and_Humidity_Sensor NanoPi M1
S Pin7
V Pin4
G Pin6

4.2 Connect to NanoPi 2

Refer to the following connection diagram to connect the module to the NanoPi 2:
Matrix-Temperature_and_Humidity_Sensor_nanopi_2

Connection Details:

Matrix-Temperature_and_Humidity_Sensor NanoPi 2
S Pin7
V Pin4
G Pin6

4.3 Connect to NanoPi M2 / NanoPi 2 Fire

Refer to the following connection diagram to connect the module to the NanoPi M2/ NanoPi 2 Fire:
Matrix-Temperature_and_Humidity_Sensor_nanopi_m2

Connection Details:

Matrix-Temperature_and_Humidity_Sensor NanoPi M2
S Pin7
V Pin4
G Pin6

4.4 Connect to NanoPC-T2

Refer to the following connection diagram to connect the module to the NanoPC-T2:
Matrix-Temperature_and_Humidity_Sensor_NanoPC-T2

Connection Details:

Matrix-Temperature_and_Humidity_Sensor NanoPC-T2
S Pin15
V Pin29
G Pin30

5 Compile & Run Test Program

Boot your ARM board with Debian and copy the matrix code: 

$ apt-get update && apt-get install git
$ git clone https://github.com/friendlyarm/matrix.git

If your cloning is done successfully a "matrix" directory will be generated.

Compile and install Matrix: 

$ cd matrix
$ make && make install

Run test program: 

$ matrix-temp_humidity

Note: this module is not plug and play therefore before running the module please make sure it is connected to an ARM board.
Here is what you should observe:

The humidity is 35000
The temperature is 26000

The module successfully read the environment's humidity and temperature values.

6 Code Sample

This Matrix code sample can work with all the ARM boards mentioned in this module's wiki. The name of this code sample is "matrix-temperature_and_humidity_sensor". Here is its source code: 

int main(int argc, char ** argv)
{
    int ret = -1;
    int dhtTemp=0, dhtHdty=0, board;
    char modStr[BUF_SIZE];
    int pin = GPIO_PIN(7);
 
    if ((board = boardInit()) < 0) {
        printf("Fail to init board\n");
        return -1;
    }    
    if (board == BOARD_NANOPI_T2)
        pin = GPIO_PIN(15);
 
    sprintf(modStr, "modprobe %s gpio=%d", DRIVER_MODULE, pintoGPIO(pin));
    system(modStr);
    if ((ret = dht11Read(DHT_HUMIDITY, &dhtHdty)) != -1) {
        printf("The humidity is %d\n", dhtHdty);
    } else {
        printf("Faided to get humidity\n");
    }
    if ((ret = dht11Read(DHT_TEMP, &dhtTemp)) != -1) {
        printf("The temperature is %d\n", dhtTemp);
    } else {
        printf("Faided to get temperature\n");
    }
    system("rmmod "DRIVER_MODULE);
    return ret;
}

For more details about this APIs called in this code sample refer to Matrix API reference manual


7 Resources

DHT11.pdf

8 Update Log

8.1 Feb-23-2016

  • Added the description for "NanoPi 2 branch" in Section 4
  • Added Section 5: Connect to NanoPi 2

8.2 June-24-2016

  • Re-organized and simplified wiki


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