Difference between revisions of "Matrix - Photoresistor"

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(编译测试程序)
(运行测试程序)
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The modules are under the "modules" directory. Its driver's source code is in https://github.com/friendlyarm/linux-3.4.y.git <br>
 
The modules are under the "modules" directory. Its driver's source code is in https://github.com/friendlyarm/linux-3.4.y.git <br>
  
===运行测试程序===
+
===Run Test Program===
将带有Debian系统的SD卡插入一台运行Linux的电脑,可以挂载SD卡上的boot和rootfs分区。<br>
+
Please insert a TF card which is flashed with Debian to a Linux host and mount its boot and rootfs sections.<br>
假设rootfs分区的挂载路径为/media/rootfs,执行以下命令将Matrix的硬件驱动、库文件和测试程序拷贝到NanoPi 2的文件系统上。<br>
+
We assume the rootfs is mounted to /media/rootfs then please run the following commands to copy the driver, library and test program to the card.<br>
 
<syntaxhighlight lang="bash">
 
<syntaxhighlight lang="bash">
 
$ cp modules /media/rootfs/ -r
 
$ cp modules /media/rootfs/ -r
Line 107: Line 107:
 
</syntaxhighlight>
 
</syntaxhighlight>
  
将SD卡重新插入NanoPi 2,上电启动,在Debian的shell终端中执行以下命令加载硬件驱动。<br>
+
Insert this TF card to your NanoPi 2, power on and run the following commands to load the driver.<br>
 
<syntaxhighlight lang="bash">
 
<syntaxhighlight lang="bash">
 
$ cd /modules
 
$ cd /modules
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</syntaxhighlight>
 
</syntaxhighlight>
  
运行模块Matrix-Photoresistor的测试程序。<br>
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Please run the following command to test the Matrix-Photoresistor module.<br>
 
<syntaxhighlight lang="bash">
 
<syntaxhighlight lang="bash">
 
$ matrix-adc
 
$ matrix-adc
 
</syntaxhighlight>
 
</syntaxhighlight>
运行效果如下:<br>
+
Here is what you should expect:<br>
 
[[File:matrix-adc_result.png|frameless||matrix-adc_result]] <br>
 
[[File:matrix-adc_result.png|frameless||matrix-adc_result]] <br>
  

Revision as of 10:51, 6 January 2016

查看中文

1 Introduction

Photoresistor
  • The Matrix-Photoresistor is a photoresistor module. It has a 3 pin 2.54mm spacing pin-header of which V is supply voltage, G is ground and s is output analog signal. The output signal decreases with increasing incident light intensity. Users can convert its output analog signal to a digital signal via ADC conversion.
  • Output Voltage: 0 ~ Vcc

2 Features

  • GPIO 3.3/5V
  • Small
  • 2.54mm spacing pin-header
  • PCB Dimension(mm): 8 x 24

Photoresistor.PCB

  • Pin Description:
Pin Description
S Analog GPIO
V Supply Voltage 5V
G Ground

3 Basic Device Operation

  • The module has a photoresistor. The resistance of a photoresistor decreases with increasing incident light intensity; in other words, it exhibits photoconductivity.If incident light on a photoresistor exceeds a certain frequency, photons absorbed by the semiconductor give bound electrons enough energy to jump into the conduction band. The resulting free electrons (and their hole partners) conduct electricity, thereby lowering resistance.

4 Download Matrix Source Code

All the matrix modules' code samples are open source. They are maintained on GitHub: https://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 nanopi2 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
Install the git utility on a PC running Ubuntu14.04

$ sudo apt-get install git

Clone the matrix code from GitHub

$ git clone https://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 2

5.1 Hardware Connection

Please refer to the following connection diagram to connect the Matrix-Photoresistor to the NanoPi 2:
Matrix-Photoresistor_nanopi_2

Connection Details:

Matrix-Analog_to_Digital_Converter NanoPi 2
SDA Pin3
SCL Pin5
5V Pin4
GND Pin6
Matrix-Photoresistor
GND NanoPi 2 Pin9
5V NanoPi 2 Pin2
S Matrix-Analog_to_Digital_Converter A0

This module's output signals are analog signals. You can use our Matrix-Analog_to_Digital_Converter to convert them to digital signals.
Please connect the Matrix-Analog_to_Digital_Converter to the NanoPi 2 and then connect Pin S of the Matrix-Photoresistor's pin header to Matrix-Analog_to_Digital_Converter's A0.
For more details about the Matrix-Analog_to_Digital_Converter module please refer to wiki:Matrix_-_Analog_to_Digital_Converter.

5.2 Compile Test Program

Please login the matrix hub and enter the nanopi2 branch

$ cd matrix
$ git checkout nanopi2

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-4.9.3" on your PC, which is used to compile files for the NanoPi 2.
Generated library files are under the "install/lib" directory. The test program is under the "install/usr/bin" directory.
The modules are under the "modules" directory. Its driver's source code is in https://github.com/friendlyarm/linux-3.4.y.git

5.3 Run Test Program

Please insert a TF card which is flashed with Debian to a Linux host and mount its boot and rootfs sections.
We assume the rootfs is mounted to /media/rootfs then please run the following commands to copy the driver, library and test program to the card.

$ cp modules /media/rootfs/ -r
$ cp install/lib/* /media/rootfs/lib/ -d
$ cp install/usr/bin/* /media/rootfs/usr/bin/

Insert this TF card to your NanoPi 2, power on and run the following commands to load the driver.

$ cd /modules
$ insmod pcf8591.ko

Please run the following command to test the Matrix-Photoresistor module.

$ matrix-adc

Here is what you should expect:
matrix-adc_result

5.4 代码展示

int main(int argc, char ** argv)
{
    int i = 0;
    int value = 0;
    int channel = 0;
 
    if (argc == 2) {
        channel = atoi(argv[1]);
    }
 
    for (i=0; i<ADC_READ_TIMES; i++) {
        if (pcf8591Read(channel, &value) != -1) {
            printf("channel%d value=%d\n", channel, value);
        } else {
            printf("Fail to get channel%d value\n", channel);        
        }
        usleep(10000);
    }
    return 0;
}