Progress update: BLE and V2

A project log for Psychic ePaper

Changeable, updatable Doctor Who psychic paper!

Thornhill!Thornhill! 03/04/2020 at 17:420 Comments


After coming up against some memory allocation issues and then solving them with some optimisation and freezing some libraries, I've moved onto playing with the ItsyBity's nRF52840 chip and it's Bluetooth LE connection. 

The main goal here is to be able to change text, images, and settings on the Psychic ePaper using a phone and a Bluetooth connection (imagine going to a convention, and being able to quickly customise an ID on the fly!). Fortunately with the CircuitPython BLE libraries and Adafruit's Bluetooth LE app, this has been very very easy. Using the example UART code from the CircuitPython BLE library and coding in a few key commands, I'm able to send messages to the Psychic and actively change text or swap images. Cosplaying as the 10th Doctor instead of the 12th? No problem! Just send the command [regenerate]10 and watch as the brooding face of David Tennant appears on the Psychic. Want to have the ID show you've been 'certified' by Rhe Convention of Doctors? Just send [title]The Convention of Doctors and it'll appear like it just read your mind!

The next step for me is storage, so that changes are not lost when the Psychic is turned off… and maybe a few advanced commands, like setting up the number and order of IDs. That'll be this week's goal!

Gif, showing a close up of an image of the 12th Doctor. View cuts to a message box, typing in the words '[Regenerate]10'. Cut back to the Psychic ePaper, and an image of the 10th Doctor replacing an image of the 12th

Version 2 progress

With version 2 I'm focusing on thinning things down and making construction easier and neater. I've started with the top half of the Psychic, which includes the e-ink display and adafruit's E-ink Friend. In version 1, both are embedded in a piece of paper/chipboard (the stuff hardback books are made out of… R.I.P Inorganic Chemistry textbook), and are connected to the micro-controller via a rat-nest of wires.

While this all works for a prototype, I think I can do a lot better for version 2!

Version 1 of the top half of the Psychic ePaper. Chipboard from a textbook holds the e-ink display (on the other side of the board) and the E-Ink Friend. The golden/orange cable is the FPC cable from the e-ink display, and the coloured wires connect from the E-Ink Friend to the micro-controller.

So far for Version 2 I've:

With all these changes, the top-half of the Psychic looks a lot neater and is now more reproducible. I'm going to have to see how durable the FFC cable is with the fold between the top and bottom half of the Psychic. Hopefully with the fabric and some strain relief, it won't be much of an issue!

ABOVE: Components that make up Version 2 of the top-half of the Psychic ePaper! The e-ink display is to the left, and the 3D printed backing to the right, with spaces and pockets modelled to fit the display and components. Towards the bottom, the thin purple FFC/FPC adapter board and a short length of white, FFC ribbon cable.
ABOVE: The components together, forming a thin package. Here you can see the front of the e-ink display (fitted into the 3D printed backing) with the white FFC ribbon cable appearing on the bottom.
ABOVE: The bottom view, showing the pieces together. The purple FFC/FPC adapter board can be seen through a window in the grey, 3D printed backing. Through this window you can also see the golden FPC cable from the display connecting to the adapter, and to the left of this connector, an adjacent connector that connects to the white FFC ribbon cable.

That's it for this project update. Next: Designing a better bottom half!