Introduction

In this tutorial series, you will learn how to use a Raspberry Pi Zero to display the current temperature on a ws2812b 32x8 LED matrix in Python.

In Part 2, we will design the number, minus sign, and degree symbol sprites and display them on ws2812b 32x8 LED matrix.

Design the sprite:

We will start by designing each number, minus sign, and degree symbol on an 8x6 matrix. You can use any tools to help with drawing.
Additionally, we will design the minus sign character in case the temperature is lower than zero degrees.
For more consistency, we will include space around the numbers and characters, as shown in the example below.

From the above design, the width is 6 and the height is 8 (this is the maximum height of the board, but for the width, you can adjust it as you like).

Apply all sprites into (x,y) coordinates:

We will start by creating a directory to keep all the coordinates.

raspberrypi
ssh pi@IP ## ssh into Raspberry Pi

cd display 

mkdir coordinate ##create draw directory

cd coordinate

touch num_coordinate.py ## create file

Inside num_coordinate.py, let’s create dictionaries that store each number as a key and the value as the x and y coordinates. You can refer to the example above.

coordinate/num_coordinate.py

numbers = {
    '0': [(1, 1), (1, 2), (1, 3), (1, 4), (1, 5), (1, 6), (2, 1), (2, 6), (3, 1), (3, 6), (4, 1), (4, 2)
    ,(4, 3), (4, 4), (4, 5), (4, 6)],
    '1': [(1, 3), (2, 2), (2, 3), (2, 4), (2, 5), (2, 6), (3, 1), (3, 2), (3, 3), (3, 4), (3, 5), (3, 6)]
}

I will give examples for 0 and 1. For other numbers, you can try it yourself.

Design a sprite class:

Let’s create sprite_painter.py inside the lib directory.
As we are designing with one color for numbers, we will call it MonochromeSprite class.

lib/sprite_painter.py

from lib.pixels import *
from typing import NamedTuple


class MonochromeSprite(NamedTuple):

    width: int
    """Width of the sprite"""

    height: int
    """Height of the sprite"""

    pixels: list[tuple[int, int]]
    """The list of pixels representing the sprite"""


def draw_pixels(
    pixels: Pixels,
    position: tuple[int, int],
    pixel_list: list[tuple[int, int]],
    color: Color
    ):
    """ Start at position x, y and draw sprite with given list of x, y coordinate with color provide """

    for pixel in pixel_list:
        x, y = pixel
        pos_x, pos_y = position
        x = pos_x + x
        y = pos_y + y

        pixels.set(x, y, color)


def draw_monochrome_sprite(
    pixels: Pixels,
    sprite: MonochromeSprite,
    position: tuple[int, int],
    color: Color
):
    """ Draw a sprite with one color """

    draw_pixels(pixels, position, sprite.pixels, color)

In the previous tutorial, we created red_dot.py, but this time we will create temperature.py inside the display directory.

display/temperature.py

from lib.pixels import *
from lib.sprite_painter import *
from coordinate.num_coordinate import numbers


if __name__ == '__main__':

    pixels: Pixels = Pixels()

    number = '0'

    for i in range(0, len(number)):

        sprite = MonochromeSprite(height = 8, width = 6, pixels = numbers[number[i]])

        position_x = i * 6 ## the starting point of first sprite at y axis will start at 0,
        ## and the next sprite will start after the previous one.

        position_y = 0 ## the starting point of y axis is always 0 for 32x8 matrix

        draw_monochrome_sprite(pixels, sprite, (position_x, position_y), Color(255, 0, 0))

    pixels.show()

Then, run sudo python temperature.py and check the result.

After you have added the coordinates of all sprites inside num_coordinate.py, you can try it out with a number like 15c or a different RGB color like (0, 255, 0) and play around with it. You should get a similar result as the first image in this tutorial. Good luck and have fun!

** Part 3 💻

Display number on ws2812b 32x8 LED matrix using Raspberry Pi [part 2]

Introduction