Reverse engineering Epaper Arduino for own image pusher

Last Updated or created 2025-01-15

To display quotes, changing once per hour.

There is not much to be found for Waveshare 4.2 Epaper.
Except for an Arduino web example.
( see https://www.waveshare.com/wiki/E-Paper_ESP32_Driver_Board )

I reversed engineered the workings, and created a python upload script to push images.

Original workings are a mess.
Per 4 bit of color, high-low switched in a byte.
Black and red separated.
Using a till p encoding over curl commands.

My implementation uses a python script called as:

python3 epaper-pusher.py ~/Downloads/Untitled.png
http://10.1.0.99/EPDI_
30 times something like 
http://10.1.0.99/ppppppppppppppppppppppppppppppppppppppppppppppppppppppaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaabbbbbbbbbbbbbbbbppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppiodaLOAD_
http://10.1.0.99/NEXT_
30 times something like
http://10.1.0.99/pbcdefghijjjjjjffffffoooooooaaabbbbbbeeeedddppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppiodaLOAD_
http://10.1.0.99/SHOW_
NOTES:
a = 0000
-
-
-
p = 1111 = 15

30 lines with 1000 bytes ( ending with iodaLOAD_ )

black pixels
first block 1
second block 0

red pixels
first block 0
second block 1

white pixels
first block 1
second block 1

PIXEL Example
RBRB
BWBW

First block 
1010 - letter K
0101 - Letter F - second nibble = white

Second block
0101 - Letter F
1111 - Letter P - second nibble white

Code

from PIL import Image
import numpy
import requests

url="http://10.1.0.99/" 

black_pixels = numpy.zeros((400,300))
red_pixels = numpy.zeros((400,300))



def classify_pixel_color(pixel):
    """
    Classify a pixel as black, white, or red.
    """
    r, g, b = pixel[:3]  # Ignore alpha if present

    # Define thresholds for classification
    if r < 128 and g < 128 and b < 128:
        return 'black'
    elif r > 200 and g > 200 and b > 200:
        return 'white'
    elif r > 128 and g < 100 and b < 100:
        return 'red'
    else:
        return None

def process_image(image_path):
    """
    Process the image and classify its pixels into black, white, or red.
    """
    image = Image.open(image_path)
    image = image.convert("RGB")  # Ensure the image is in RGB mode

    width, height = image.size
    pixel_data = image.load()

    color_counts = {'black': 0, 'white': 0, 'red': 0}

    for y in range (0, 299):
        for x in range (0, 399):
            black_pixels[x][y] = 0
            red_pixels[x][y] = 0

    for y in range(299):
        for x in range(399):
            color = classify_pixel_color(pixel_data[x, y])
            if color:
                color_counts[color] += 1
                if color == 'black':
                    black_pixels[x][y] = 1;
                if color == 'red':
                    red_pixels[x][y] = 1;
                if color == 'white':
                    black_pixels[x][y] = 1;
                    red_pixels[x][y] = 1;

    return color_counts, black_pixels, red_pixels

def number_to_letter(num):
    """
    Translates a number from 0 to 15 into a corresponding letter (a-p).

    Args:
        num (int): The number to translate.

    Returns:
        str: The corresponding letter (a-p).
    """
    if 0 <= num <= 15:
        return chr(ord('a') + num)
    else:
        raise ValueError("Number must be between 0 and 15, inclusive.")

def print_array_in_chunks(array, chunk_size=1001):
    current_chunk = ""
    for item in array:
        # Convert item to string and add to the current chunk
        item_str = str(item)
        if len(current_chunk) + len(item_str) + 1 > chunk_size:
            # Print the current chunk and reset it
            current_chunk += "iodaLOAD_"
            try:
                requests.get(url + current_chunk, verify=False)
                if not response.content:  # Equivalent to expecting an empty reply
                    pass
            except requests.exceptions.RequestException as e:
                # Catch any request-related errors
                pass
            current_chunk = item_str
        else:
            # Append the item to the current chunk
            current_chunk += (item_str)
    current_chunk += "iodaLOAD_"
    # Print any remaining items in the chunk
    if current_chunk:
        try:
            requests.get(url + current_chunk, verify=False)
            if not response.content:  # Equivalent to expecting an empty reply
                pass
        except requests.exceptions.RequestException as e:
            # Catch any request-related errors
            pass
        

def switch_in_pairs(arr):
    # Loop through the array with a step of 2
    for i in range(0, len(arr) - 1, 2):
        # Swap values at index i and i+1
        arr[i], arr[i + 1] = arr[i + 1], arr[i]
    return arr

if __name__ == "__main__":
    import sys

    if len(sys.argv) < 2:
        print("Usage: python3 script.py <image_path>")
        sys.exit(1)

    image_path = sys.argv[1]
    try:
        color_counts, black_pixels, red_pixels = process_image(image_path)
        try:
            requests.get(url + "EPDI_" , verify=False)
            if not response.content:  # Equivalent to expecting an empty reply
                pass
        except requests.exceptions.RequestException as e:
            # Catch any request-related errors
            pass

        
        lines=[]
        for y in range(300):
            for x in range(0,399,4):
                first = red_pixels[x][y]
                second = red_pixels[x+1][y]
                thirth = red_pixels[x+2][y]
                fourth = red_pixels[x+3][y]
                nibble = 0
                if (first ==  1):
                        nibble = nibble + 8
                if (second ==  1):
                        nibble = nibble + 4
                if (thirth ==  1):
                        nibble = nibble + 2
                if (fourth ==  1):
                        nibble = nibble + 1
                lines.append(number_to_letter(nibble))
        switched_array = switch_in_pairs(lines)
        print_array_in_chunks(switched_array)
        try:
            requests.get(url + "NEXT_" , verify=False)
            if not response.content:  # Equivalent to expecting an empty reply
                pass
        except requests.exceptions.RequestException as e:
            # Catch any request-related errors
            pass
        lines=[]
        for y in range(300):
            for x in range(0,399,4):
                first = black_pixels[x][y]
                second = black_pixels[x+1][y]
                thirth = black_pixels[x+2][y]
                fourth = black_pixels[x+3][y]
                nibble = 0
                if (first ==  1):
                        nibble = nibble + 8
                if (second ==  1):
                        nibble = nibble + 4
                if (thirth ==  1):
                        nibble = nibble + 2
                if (fourth ==  1):
                        nibble = nibble + 1
                lines.append(number_to_letter(nibble))
        switched_array = switch_in_pairs(lines)
        print_array_in_chunks(switched_array)

        try:
            requests.get(url + "SHOW_" , verify=False)
            if not response.content:  # Equivalent to expecting an empty reply
                pass
        except requests.exceptions.RequestException as e:
            # Catch any request-related errors
            pass

    except Exception as e:
        pass

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