Tricked.dev

Rickrolling with a TSPL lcd

Introduction

Most of us are familiar with printers and their primary function - printing. But what if I told you that a label printer could become an instrument of wholesome trolling? That’s right, I managed to rickroll everyone using a TSPL printer’s LCD. Here’s how it all began.

Decoding the TSPL Printer

First, let’s demystify the term. TSPL, or Thermal Printer Command Language, is a command set mainly used for label printing. The idea of playing a video on such a device may seem bizarre. But sometimes, the journey is just for the sheer joy of experimentation.

Downloading Files onto the Printer

My initial exploration led me to discover a method to download files onto a TSPL printer, allowing them to be utilized for printing or, in this case, to have some fun.

Utilizing functions I previously created for Writing TSPL on linux, I devised the following code:

let mut data: Vec<u8> = vec![];


data.extend("DOWNLOAD \"frame.bmp\"\n".to_owned().as_bytes());
data.extend(&binary);
data.extend("\nEOP\n".to_owned().as_bytes());
write_binary(&data)?;

This code essentially instructs the printer to download a file named frame.bmp, followed by appending the file’s binary content and finally signaling the end of the procedure with EOP.

The Rickroll Setup

With the ability to download files onto the printer, I embarked on a whimsical journey to rickroll unsuspecting souls. Using `yt-dlp“, I downloaded the infamous ‘Never Gonna Give You Up’ video. To make it suitable for the printer’s display, I then used ffmpeg to resize and reduce its framerate. The video was then split into individual frames to create the final animation.

Terminal window
yt-dlp "https://youtu.be/dQw4w9WgXcQ?si=6yzQp08qKwLu6h7u"
ffmpeg -i Rick\ Astley\ -\ Never\ Gonna\ Give\ You\ Up\ \(Official\ Music\ Video\)\ \[dQw4w9WgXcQ\].webm -vf "scale=320:240" -r 10 resized_video.mp4
# the first 20 seconds at 10fps
ffmpeg -i resized_video.mp4 -vframes 200 frames/frames_%04d.bmp

Animation in Action

The final step involved sending these frames to the printer and sequentially displaying them, creating a mini rickroll animation on the printer’s LCD:

write_text("\r\nCLS\r\nDISPLAY 16777215,16711680\r\nDISPLAY CLS\r\n".to_owned())?;


for file in fs::read_dir("frames").unwrap() {
    let binary = fs::read(file?.path())?;
    let mut data: Vec<u8> = vec![];
    data.extend("DOWNLOAD \"frame.bmp\"\n".to_owned().as_bytes());
    data.extend(&binary);
    data.extend("\nEOP\n".to_owned().as_bytes());
    data.extend("DISPLAY 0,0,\"frame.bmp\"\r\n".to_owned().as_bytes());
    write_binary(&data)?;
    std::thread::sleep(Duration::from_millis(100))
}
write_text("DELAY 5000\r\nDISPLAY OFF\r\n".to_owned())?;

An interesting optimization for future endeavors might involve preloading all frames onto the printer’s 8MB RAM. This would enable smooth playback without any intermittent ‘downloading’ messages.

Conclusion

This experiment with a TSPL printer underscores the unexpected fun that can emerge from everyday tech. While playing videos on a printer’s LCD might seem unconventional, it’s a whimsical reminder that with a dash of creativity, we can uncover delightful possibilities in the most ordinary places.

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