Matrix - IR Receiver

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1 Introduction

IR Receiver

• Matrix-IR Receiver是38KHz红外接收模块，主要器件是一个红外接收头，可接收标准38KHz调制的遥控器信号，并放大和滤波输出，通过MCU编程，即可实现对遥控器信号的解码操作。
• 接收范围：12-13米

2 Features

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

• Pin Description:

Pin	Description
S	GPIO
V	Supply Voltage 5V
G	Ground

3 Basic Device Operation

• 红外接收头内部包括红外监测二极管、放大器、限副器、带通滤波器、积分电路、比较器等。红外监测二极管检测到红外信号，然后把信号送到放大器和限幅器，限幅器把脉冲幅度控制在一定的水平，而不论红外发射器和接收器的距离远近。交流信号进入带通滤波器（带通滤波器可以通过30khz到60khz的负载波），再通过解调电路和积分电路进入比较器，比较器输出高低电平，还原出发射端的信号波形。
• 注意:输出的高低电平和发射端是反相的，这样的目的是为了提高接收的灵敏度。

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 matrix-nanopi branch contains the matrix modules' code samples for the NanoPi
• The matrix-nanopi2 branch contains the matrix modules' code samples for the NanoPi 2
• The matrix-tiny4412 branch contains the matrix modules' code samples for the Tiny4412;
• The matrix-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-IR_Receiver to the NanoPi 2:

Connection Details:

Matrix-IR_Receiver	NanoPi 2
S	Pin7
V	Pin4
G	Pin6

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.

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 module, 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 matrix_ir_recv.ko

If the driver is successfully loaded a device node will be generated under /dev/input/. In our test case the node was event1.

There is an open source utility "input-utils" which can be used to read the event device's data. Here is how it works:

$ apt-get install input-utils
$ input-events 1

1 stands for device node "event1"

You can use a regular remote control to send signals to it. Here is what you expect to observe: