piDraw

PiHATDraw

RasberyPi Sense HAT is a device that is connected to a raspberry Pi and includes several additional hardware and sensors. Two of them are a 8X8 LED display and a joystick.

This software should run on a raspberry pi with a hat. It uses the hat to draw: the display is a "floating" window - a subset of the bigger canvas. To draw, move the cursor to the required pixel and press the joystick to set the pixel.

The software also starts a web application that serves an HTML page to display the full draw. The cell with the X is the cursor location.

The web display also include the following controls:

• Color picked - to change the color of the cursor: pressing the joystick will set the pixel to this color.
• The Reset button: clear the draw, set the cursor and the window to their default position and the color to the default color.
• Pick Color From Pixel - change the color to the color of the color of the cell that the cursor is pointing to.
• Download Image:
  • Select the download image "pixel" (square) size in real pixels. Choose between 1, 2, 3 (default), 5, 10 or 20 (original size) pixels.
  • Download button to download the image file.

How to Build and Run

I checked this on raspberry pi 2B with a Sense HAT, with golang version 1.15.8

Just installing golang on raspberry pi will give you an old version of go. Better way is to download and install the latest version:

Got to golang download page and get the file for armv6l. Currently it's go1.15.8.linux-armv6l.tar.gz

You can use the instructions here for the installation.

After that, clone this project in a directory in your go path, e.g. ~/go/src/github.com/nunnatsa:

git clone https://github.com/nunnatsa/piDraw.git

Now build the software:

cd piDraw
go build .

If everything went fine, the new piDraw executable file is created. Go on and run it:

./piDraw

You can now draw with the HAT joystick on the HAT display.

When on the same network as your raspberry pi, open a web browser and go to your raspberry pi hostname in port 8080, the default is http://raspberrypi:8080/

Now you can see the full drawing. Notice that the page is sync with the HAT. Open another tab or browser and noticed that both of them are updated simultaneity.

Command line parameters:

The software support 3 optional parameters:

• --port - to override the default 8080 webapp port.
• --width - the canvas width in unit of windows (8-pixels); e.g. setting 3 will produce width of 24. The default is 3, and the valid values are 1 - 5.--width - the canvas width in unit of windows (8-pixels); e.g. setting 3 will produce width of 24. The default is 3, and the valid values are 1 - 5.
• --height - the canvas height in unit of windows (8-pixels); e.g. setting 3 will produce height of 24. The default is 3, and the valid values are 1 - 5.--width - the canvas width in unit of windows (8-pixels); e.g. setting 3 will produce width of 24. The default is 3, and the valid values are 1 - 5.

Running not from Raspberry Pi

It is also possible to run from a PC (only tested on Linux). Instead of the joystick, use the arrow keys to move the cursor and Enter key to paint the pixel.

The Software

See here.