TRMNL is a 7-5-inch wireless E-Ink display based on an ESP32-C3 RISC-V WiFi and Bluetooth SoC and designed to be customizable, allowing users to disassemble their device, modify the (open-source) firmware, and retrieve API keys without voiding the warranty.
The default 1,800 mAh battery is good enough for over 3 months on a charge, but the company also provides an option for a 2,500 mAh battery that is said to last for more than 6 months (not sure how the math works here). The wireless display can be placed on a desktop, or mounted on a wall or a fridge.
TRMNL specifications:
- Wireless MCU – Espressif ESP32-C3
- Display – 7.5″ black and white E-Ink display with 800 x 480 resolution
- Battery – 1,800mAh rechargeable lithium (2,500mAh upgradeable for 6+ months on a charge)
- Dimensions – 171 x 116 x 10mm
- Weight – 165 grams
- Enclosure – Soft-touch ABS (Black only), chrome-plated steel kickstand
The wireless display ships with a case opener, and optional accessories include a USB-C cable, a screen protector, and a microfiber.
The firmware is open-source and can be found on GitHub along with API documentation, power consumption measurements, and instructions to build the code from source. The documentation website goes into more detail about the firmware and software design. It’s basically a client <-> server implementation where the TRMNL firmware sends requests for content, plugins, or firmware to the server.
It’s also possible to recycle an old Kindle device with the TRMNL firmware. The server also hosts a range of native and custom plugins. The latter requires a one-time $20 developer license fee.
Native plugins give the ability to display RSS feeds, show a slideshow of photos, display the weather, show a Bitcoin or Ethereum wallet, calendars from Outlook or Google, the Hacker News feed, a shopping list, and so on. There are currently 82 such plugins.
We’ve seen many ESP32-based wireless E-Ink displays in the past, especially the Inkplate family, but also the M5Paper 4.7-inch e-Ink touchscreen display, LILYGO 7.5-inch E-paper display for T5 board, and many others. In one way or another, all those wireless E-Ink displays are customizable, but they often need to be programmed with Arduino, MicroPython, etc… The TRMNL display looks easier to use as its firmware allows end users to directly load plugins for common use cases.
The TRMNL was initially launched through a Kickstarter campaign at the end of last month, but it’s now available on the company’s online store for $139 and up, depending on the selected color.
Via Liliputing
Jean-Luc started CNX Software in 2010 as a part-time endeavor, before quitting his job as a software engineering manager, and starting to write daily news, and reviews full time later in 2011.
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Wait 2 months and we will see clone in Aliexpress for half the price.
Already happened. Not tried the trmnl software yet though. https://www.seeedstudio.com/XIAO-7-5-ePaper-Panel-p-6416.html?utm_source=cnx_software&utm_medium=link&utm_campaign=cnx_software
I somehow missed that one in my list. The specs are almost the same, although the TRMNL is thinner.
https://www.cnx-software.com/2025/04/04/seeed-studio-xiao-7-5-epaper-panel-supports-esphome-firmware-arduino-programming/
I am absolutely not a programmer at all but I wonder if the software could be cross-compatible.
If you check the Hacking Guides section at the bottom of the GitHub page, you can see that TRMNL can also be run on the development machine.
But if you want to run it on a different microcontroller, you’d need to change the code.
Some of those plugins must kill battery life in an instant…
Very cool using an old Kindle and just run this as an app!
Looking at the video for Bring Your Own Server and looking at the source code on Github for wificaptive source client, I only see IPv4 values so it would appear that the current state of this device does not support IPv6 networking. (And yes http://www.cnx-software.com is IPv6 operational which is how I connect.) For a device which is aiming to be “future-proof flexible”, this seems like a glaring omission in its foundations. Maybe IPv6 connectivity will get added at a later time?