Using an OpenFrame as a TRMNL

[roobarb!]

I've always loved e-ink displays, so when I found out about TRMNL I had to order one. The hardware is just a custom ESP32 board with battery, charging circuit and a 7.5" 800x480 e-ink panel. The idea is that you can use it as a very-low-power status display. It just fetches a bitmap image from a server (theirs, or you can run the server locally) with the images generated based upon first and third-party "plugins", which are really just a little bit of fetch code with HTML on the side.

It's not with me yet, but the team have opened up the server interface for anyone waiting on delivery, which is how I ended up playing with it. You can also just pay them a few dollars a year for use of their server and not order a display at all.

The cute coincidence is the 800x480 bitmap image, or rather the 5:3 ratio. The nature of e-ink (in this case) means it's just 1-bit, but perfectly sized for our OpenFrame displays. I've been able to use:

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fbi -vt 1 -noverbose someimage.bmp

to dump the image into the tty1 framebuffer. You can try it with:

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wget -q -O unsplash_wallpaper.jpg https://unsplash.it/800/480/?random; fbi -vt 1 -noverbose unsplash_wallpaper.jpg

if you just want to throw a random image on screen.

Next, because the OpenFrames are thousands of times more powerful than the ESP32, I'm going to experiment with using the TRMNL-server-generated bitmaps as adjustment layers with ImageMagick, to "snazz up" the display with random images or pics from our photo library. Fun times!