trmnlocal

Local Node.JS host that can be used as a TRMNL API server. Tested on macOS and Ubuntu.

Renders a webpage of your choice via Puppeteer, by default every ~20 seconds (but can be made faster/slower). Passes some state in the URL: device ID, rssi, etc.

Renders 2-bit PNGs. See a demo.

Usage

Install this package via npm or friends, and run trmnlocal (possibly from your global path). For instance:

$ npm install -g trmnlocal
$ trmnlocal -u https://samthor.au/trmnlocal

This will run a server that you can point your TRMNL device to, in the Advanced setup. Use your machine's IP address and the port (e.g., "http://192.168.0.141:8080").

You might want to run this in a more long-term way somewhere. Up to you!

On Ubuntu/Linux

To run this on a headless Ubuntu/Linux environment, I needed these additional packages:

sudo apt install libxdamage1 libxcomposite-dev libatk-bridge2.0-0

But also, don't run random commands as sudo from randoms on the internet.

Demo

You can load "/render" (e.g., "http://localhost:8080/render") to render the 2-bit PNG just for local testing.

Flags

You can specify some flags:

• -u <url> the URL to show
• -r <refresh seconds> how many seconds to wait to rerender
• -d <rotate, 0/90/180/270> rotate the rendered output
• -p <port> port to run on, uses $PORT or 8080 as default

Warnings

This runs Puppeteer, aka headless Chrome, to render your content. Don't point this at a page you don't trust.

We check the rendered image and don't refresh the TRMNL unless the bytes change. However, Chrome tends to be somewhat inconsistent on this front, so you might see refreshes more often.

Part of the reason the TRMNL doesn't re-render constantly is to extend the lifecycle of the device. If this refreshes your device constantly, - well, you've been warned!

Goals

I built this because I don't want a full experience, I just want a slimmed down way to render content. It won't ever provide all the features of the 'community' backends.

TODOs

• Rotate is global, it should be configurable per device ID which fetches data
• Proxy to TRMNL's real API to check for firmware updates