use. Net drives the OLED display of Jetson nano

background

Recent years , The demand for edge computing has exploded . Artificial intelligence 、 Internet of things and 5G The evolution of brings infinite possibilities to edge computing . Because of work , I'm lucky to be here 2019 Began to contact NVIDIA Jetson Family of edge computing devices ：Nano,TX2,AGX,NX etc. , Its operating system uses Ubuntu 18.02. We can use it as an independent small server , Which programmer would refuse to own a small computer of his own ？ On top of it , Especially having GPU On , We can toss about infinite possibilities .

stay Jetson The development version of the equipment is on the board , There is usually one 40 Pin pin SPIO And GPIO, Through it, we can expand more interesting things . for instance ： A piece of I2C Of OLED display , And then through .Net To drive it to show something fun （ Software status , Equipment status , Other key data indicators ）.

Screen installation

The screen here is a piece 0.96 Inch yellow and blue OLED LCD module , altogether 4 Interface ：3.3V Positive pole VCC, Negative pole GND, And responsible for I2C Communicating SDA and SCL.

So how to connect the monitor with Jetson The equipment is connected ？ The demonstration here is based on the earlier Nano Carrier board of Developer Suite , The pins of other series of official carrier boards are basically similar , You can also find the hardware specification or Refer to the guidelines on the official website To find the I2C Interface can .

I'm using I2C1, The pin connected is 1,3,5,6 , Install as defined OLED display .

To configure I2C Bus

After installing the screen , Must be configured I2C, Only our own login account can be in non Root Access... Under permission I2C Bus .

Put the following command username Change to your login account name

sudo usermod -aG i2c username

Better restart the device , If you execute the following command, it can be displayed normally , Then there's no problem .

i2cdetect -y -r 1

In the following illustration ,OLED Address of the display 3c Be particularly highlighted .

use .NET Drive display

Drive this oled Screen we need to use Microsoft IoT Related libraries “System.Device.Gpio” , Through this library, we can realize the connection with external devices I2C Communications , Of course drive OLED The display needs to use various instructions familiar with its driver chip , The driver chip here is SSD1306, Have the biggest 128*64 Pixel support , Widely used in small size OLED The drive of the display screen .

Here we won't introduce the related drivers and instructions , I have encapsulated the relevant instructions into a library , You can use it directly , Open source library , Interested students can consult relevant knowledge and source code by themselves .

Now let's go through Jetson Nano Show how to use “Sang.IoT.SSD1306” Library to control OLED display frame .

install .Net development environment

because Jetson yes arm64 The equipment , Let's go straight to .Net Choose to download from the official website .Net6 Of Arm64 edition .

Execution and installation

mkdir -p $HOME/dotnet && tar zxf dotnet-sdk-6.0.301-linux-arm64.tar.gz -C $HOME/dotnet

Then change the user directory .bashrc file , Add the following environment configuration at the end ：

export DOTNET_ROOT=$HOME/dotnet
export PATH=$PATH:$HOME/dotnet

function dotnet Command to check the installation .

Using the demonstration

Create a console program

dotnet new console -o i2c_oled

Add driver library

dotnet add package Sang.IoT.SSD1306

Modify the code

using Sang.IoT.SSD1306;

using (var oled = new SSD1306_128_64(1)) {
    
    oled.Begin();
    //  The display content that needs to be sent to the display 
    byte[] c = new byte[128*64]{
    ...};
    oled.SetBuffer(c);
    oled.Display();
}

To display the array data to the screen , You need to store the data in SSD1306 Of RAM. there RAM The size is 128x64 position , It is divided into 8 page , from 0 Page to 7 page , For monochrome 128x64 The dot matrix shows .

The above code may not be used at ordinary times , It is mainly a customized content display interface .

Picture shows

The class library here uses Microsoft SkiaSharp Cross platform image processing library , About cross platform image processing library , If you have a need , Sure Look at this article to compare .

The pictures used for demonstration here are as follows , We put it in OLED The display shows .

Original image address ：https://raw.githubusercontent.com/marin1993/Sang.IoT.SSD1306/master/assets/test.png

using Sang.IoT.SSD1306;

using (var oled = new SSD1306_128_64(1)) {
    
    oled.Begin();
    oled.Image("assets/test.png");
    oled.Display();
}

The effect is as follows ：

According to the text

that , How to display text ？ Of course , The same way of thinking , We first pass SkiaSharp Create a bitmap , Then display it , So it's not difficult to load font files to display Chinese fonts .

using Sang.IoT.SSD1306;
using SkiaSharp;

using (var oled = new SSD1306_128_64(1)) {
    

    oled.Begin();
    oled.Clear();

    using(var bitmap = new SKBitmap(128, 64, true)){
    
        SKCanvas canvas = new SKCanvas(bitmap);
        SKPaint paint = new SKPaint() {
     
            Color = new SKColor(255, 255, 255),
            StrokeWidth = 1, // The width of the brush 
            Typeface = SKTypeface.FromFile("/home/sangsq/i2c_led/SourceHanSansCN-Normal.ttf"),
            TextSize = 13,  // font size 
            Style = SKPaintStyle.Fill,
        };
        canvas.DrawText(" official account ：sangxiao99 ", 0, 13, paint);
        paint.TextSize = 30;
        canvas.DrawText(" Sang Yu Xiao Wu  ", 0, 50, paint);
        oled.Image(bitmap.Encode(SKEncodedImageFormat.Png, 100).ToArray());
    }

    oled.Display();
}

The effect is as follows ：

Clear the display

oled.Clear();

Conclusion

If the IoT If you are interested in this field or want to toss the development board at hand , You can go to the official website to learn more .Net Of IoT resources .

Just arrived at a SPI Interface LCD Color display , There are new toys to play with .