Matrix - Temperature Sensor

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1 Introduction

Temperature Sensor

• The matrix-temperature_sensor module is used to measure temperature.
• We utilitze the DS18B20 chip with the To-92 package in this module. Its unique 1-wire interface requires only 1 port pin for reading/writing. Power for reading, writing, and performing temperature conversions can be derived from the data line itself with no need for an external power source. The DS18B20 can be powered from its data line. Each DS18B20 is assigned a unique ID.
• Its temperature range is -55 degree Celsius to +125 degree Celsius. The thermometer resolution is programmable from 9 to 12 bits. When the measured temperature is between -10 degree Celsius to +85 degree Celsius the accuracy can be at 0.5 degree. Among all three DS18B20 pins V is power, G is ground and S is data.

2 Features

• -55 degree Celsius to +125 degree Celsius
• One wire interface for communication
• Tiny, easy to be deployed in various situations
• 2.54mm spacing pin
• PCB dimension(mm): 8 X 24

• Pin Description:

Pin	Description
S	GPIO
V	Power 5V
G	Ground

3 工作原理

DS18B20低温度系数晶振的振荡频率受温度影响很小，用于产生固定频率的脉冲信号送给计数器1。高温度系数晶振随温度变化其振荡率明显改变，所产生的信号作为计数器2的脉冲输入。计数器1和温度寄存器被预置在-55℃所对应的一个基数值。计数器1对低温度系数晶振产生的脉冲信号进行减法计数，当计数器1的预置值减到0时，温度寄存器的值将加1，计数器1的预置将重新被装入，计数器1重新开始对低温度系数晶振产生的脉冲信号进行计数，如此循环直到计数器2计数到0时，停止温度寄存器值的累加，此时温度寄存器中的数值即为所测温度。

4 Download Matrix Source Code

All the matrix modules' code samples are open source. They are maintained in a git hub - git://github.com/friendlyarm/matrix.git
Each branch in this hub contains the matrix modules' code samples for a board that the matrix modules can work with.

• The nanopi branch contains the matrix modules' code samples for the NanoPi
• 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:
Install the git utility on a PC running Ubuntu14.04

$ sudo apt-get install git

Clone the matrix code hub

$ git clone git://github.com/friendlyarm/matrix.git

If this is successful a "matrix" directory will be generated, which will contain all the matrix modules' code samples.

5 Connect to NanoPi

5.1 Preparations

Please install a Debian on a NanoPi and an appropriate cross compiler on a PC. Please refer to wiki: NanoPi
Compile a NanoPi kernel. Note: please use the kernel's source code from the nanopi-v4.1.y-matrix branch

$ 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

5.2 Hardware Connection

Please refer to the following connection diagram to connect the Matrix-Temperature_Sensor module to the NanoPi

Connection Details:

Matrix-Temperature Sensor	NanoPi
S	Pin7
V	Pin4
G	Pin6

5.3 Compile Test Program

Please login the matrix hub and enter the nanopi branch

$ cd matrix
$ git checkout nanopi

Compile the matrix code

$ make CROSS_COMPILE=arm-linux- clean
$ make CROSS_COMPILE=arm-linux-
$ make CROSS_COMPILE=arm-linux- install

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.
Generated library files are under the "install/lib" directory. Applications are under the "install/usr/bin" directory. The test program for the "Matrix-Temperature_Sensor" module is "matrix-temperature_sensor".

5.4 运行测试程序

拷贝库文件和测试程序到NanoPi的文件系统上

$ cp install/usr/bin/* nanopi_rootfs/usr/bin/
$ cp install/lib/* nanopi_rootfs/lib/ -d

然后启动NanoPi，在Debian的shell终端中执行如下命令运行模块Matrix-Temperature_Sensor的测试程序
注意：此模块并不支持热插拔，启动系统前需要确保硬件正常连接。

$ matrix-temperature_sensor

5.5 代码展示

int main(int argc, char ** argv)
{
    int devFD = -1;
    int pin = GPIO_PIN1;
    char *temperature = (char *) malloc(32);
    memset(temperature, 0, 32);
 
    if (argc == 2) {
        parseCmd(argc, argv, &pin);
    } else {
        printf("Using default pin GPIO_PIN1\n");
    }
 
    if ((devFD = ds18b20Init(pin)) == -1) {
        printf("Fail to init ds18b20\n");
        return -1;
    }
    if (ds18b20Read(temperature) > 0) {
        printf("Temperature = %s\n", temperature);
    } else {
        printf("Fail to get temperature\n");		
    }
    free(temperature);
    ds18b20DeInit(devFD);
    return 0;
}

6 与Tiny4412连接使用

6.1 准备工作

参考Tiny4412光盘里的《友善之臂Ubuntu使用手册》，在Tiny4412上运行UbuntuCore系统，然后在主机PC上安装并使用相应的编译器。
注意：只能使用Tiny4412SDK-1506的底板。

6.2 硬件连接

参考下图连接模块Matrix-Temperature_Sensor和Tiny4412

连接说明：

Matrix-Temperature Sensor	Tiny4412
S	GPIO1 S
V	GPIO1 5V
G	GPIO1 GND

6.3 编译测试程序

进入Matrix代码仓库，切换到tiny4412分支

$ cd matrix
$ git checkout tiny4412

编译Matrix配件代码

$ make CROSS_COMPILE=arm-linux-gnueabihf- clean
$ make CROSS_COMPILE=arm-linux-gnueabihf-
$ make CROSS_COMPILE=arm-linux-gnueabihf- install

注意：请确保你的主机PC当前使用的交叉编译器为Tiny4412-UbuntuCore配套的arm-linux-gnueabihf-gcc-4.7.3。
编译出来的库文件位于install/lib目录下，而测试程序则位于install/usr/bin目录下，模块Matrix-Temperature_Sensor对应的测试程序为matrix-temperature_sensor。

6.4 运行测试程序

拷贝库文件和测试程序到Tiny4412的UbuntuCore的文件系统上

$ cp install/usr/bin/* tiny4412_rootfs/usr/bin/
$ cp install/lib/* tiny4412_rootfs/lib/ -d

然后启动Tiny4412，在UbuntuCore的shell终端中执行如下命令运行模块Matrix-Temperature_Sensor的测试程序
注意：此模块并不支持热插拔，启动系统前需要确保硬件正常连接。

$ matrix-temperature_sensor

6.5 代码展示

int main(int argc, char ** argv)
{
    int devFD = -1;
    int pin = GPIO_PIN1;
    char *temperature = (char *) malloc(32);
    memset(temperature, 0, 32);
 
    if (argc == 2) {
        parseCmd(argc, argv, &pin);
    } else {
        printf("Using default pin GPIO_PIN1\n");
    }
 
    if ((devFD = ds18b20Init(pin)) == -1) {
        printf("Fail to init ds18b20\n");
        return -1;
    }
    if (ds18b20Read(temperature) > 0) {
        printf("Temperature = %s\n", temperature);
    } else {
        printf("Fail to get temperature\n");		
    }
    free(temperature);
    ds18b20DeInit(devFD);
    return 0;
}

9 相关资料

DS18B20.pdf