What is CALE?

CALE is a screen administrator where you can mix content of different APIs and control the content output

Practical uses

  • Meeting room sign that updates every hour showing next meetings and attendees
  • Living picture, showing events or Cloudwatch statistics
  • Help screens at the side of your laptop, refreshing dynamic information every 10 minutes
  • Any other application you may find interesting to see in real-time outside the monitor
We can integrate any external API in a question of hours. This is open-source and free for personal use up to 3 Screens.

What it does in two simple steps:

  1. CALE receives a request from your Screen
  2. Returns a response with an image or HTML if you want to use it anywhere in the web
This output can be exported as a bitmap image and can be used to refresh dynamically WiFi online displays such as Epaper or Eink displays that are online using ESP32 or ESP8266 to run their Firmware. But you can use it also to display this API mixins in your monitor, tablet or any device. CALE is free for personal use and supports up to 3 different Screens. If you need to use it for business use supporting more Screens please get in touch with us on the support section after registering an account. Check our Firmware for ESP32/ESP8266 and the supported E-ink displays in order to build one of this displays yourself. Additionally we recently added support for TFT Displays (Firmware coming at the beginning of April 2020)

Electronic Ink

Primary target displays are the so called Eink or Epaper. The technical term is electrophoretic ink, that when laminated to a plastic film and then adhered to electronics, it creates an Electronic Paper Display (EPD). The ones that expose an SPI interface for makers come in up to 2 EInk colors, 3 colors counting the white background, but in the first version of this Screen administrator tool we are targeting only the ones with Black ink (2 colors).

Eink is made of millions of tiny microcapsules

This particles are the diameter of human hairs. We are supporting many EPD displays using the library GxEPD
Each microcapsule contains electrically charged particles

When an electrical field is applied the microcapsules with opposite sign float to the top of the display, creating a crisp image that can be seen withouth any backlight.

And how this is supposed to work automatically

Right now what the Firmware does is very simple:

  • Wakes up, connects to your WiFi, and reads an image from CALE
  • This image URL and authorization token you can get when you log in and compose your Screens
  • The firmware sends the image to the Eink display and goes to sleep a predefined time (Ex. one hour) > Repeats the loop waking up again
Optionally to save more energy, since the consumption peak is getting online, we are building mechanisms to compare the hour and run it only on the desired time. This is prototyped and just needs to be documented, but essentially boils down to 2 points:

  1. CALE API will provide an endpoint where you can query the right time for Timezone (Ex. now is 9 AM)

  2. The firmware will only fetch the image and send it to the display if the hour checked in Point 1 is between the "update display" hour range. For example if the update range is from 10 to 22 Hrs then the display will wake up at 9, check the time from the API and go to sleep one hour more without doing anything. In next wake up at 10 it will effectively see it's on the range and refresh the display.
Connecting for 2 seconds to make this very short API call is a very short consumption peak that the 10 seconds that takes to download a medium sized bitmap and to send it via SPI to the display. As a second point, EInk displays have a factory lifespan of 1 million prints, so we would like that the Screen is only refreshed optimally both saving precious battery lifespan and the life of your display.