Pervasive Displays e-Paper BWR Screens

This is a revised version of the second generation of the Pervasive Displays e-Paper EPD Extension Kit Gen 2. It supports the new black-white-red screens with a 24 flat connector.

Pervasive Displays has launched new e-paper screens featuring three colours black-white-red and larger diagonals.
  • iTC 4.2" BWR screen with 300 x 400 pixels
  • iTC 7.4" BWR screen with 800 x 480 pixels
  • iTC 12.2" BWR screen with 960 x 768 pixels

​The screens were sampled by Pervasive Displays.
Most of the screens featuring black-white-red are also available with black-white-yellow, to be used with the same Pervasive Displays e-Paper EPD Extension Kit Gen 2.

​Learn more at Pervasive Displays e-Paper BWY Screens.

Hardware

Those screens inaugurate a more compact flat cable with 24 ways only.

​The Pervasive Displays e-Paper EPD Extension Kit Gen 2 adds a new ZIF connector accordingly.
The flat cables from the screens are longer, making the connection easier.
All the screens require the same configuration on the back on the board. ​Set the DIP switches to 01010100, according to the explanations printed just below. 
Because the screens are made of glass, they are rather fragile. The iTC 7.4" BWR comes with a back reinforced with a bakelite plate.

​This is a very nice addition. Let's hope other large screens like the iTC 4.2" BWR and iTC 12.2" BWR are going to benefit as well.

Software

Pervasive Displays provides a GitHub repository with examples for each screen. However, those examples do not leverage the built-in 8 Mb / 1 MB Flash.

One major innovation is that the new screens no longer require two frame-buffers, one for the previous image and another for the next image. Having one single frame-buffer saves a lot of RAM.

However, larger screens mean larger buffers, up to 180 kB for the iTC 12.2" BWR, as per the table shown on the right. 
​
​Similarly, refreshing the larger screens takes longer, up to 45 seconds for the massive iTC 12.2" BWR.

Integrating the new screens to the LCD_screen Library Suite was easy thanks to the examples provided. The library now leverages the 8 Mb / 1 MB Flash of the Pervasive Displays e-Paper EPD Extension Kit Gen 2 to store the fonts, slashing the memory foot-print on the MCU. 
Updating the iTC 7.4" BWR takes 32 seconds, and the iTC 4.20" BWR 19 seconds.

​Smaller screens require less than 15 seconds typically.
All the iTC BWR screens provide resolution superior to 110dpi.

​The smallest iTC 1.54 BWR screen tops with 140dpi, perfect for QR-code.

Even with one dot, the QR-code is read and recognised as a link by the iPhone.

​The QR-code is actually real and points to this very page.
The high resolution allows to combine the colours to obtain new shades. 
​
  • Black and white give grey.
  • Red and white give light red.
  • Red and black give dark red.

Conclusion

I am very happy with the iTC BWR new screens, especially those with a ratio close to 1.5 (1.33~1.67).
The larger area gives space for more elaborated dashboards, the red colour is a clear differentiator, the single frame-buffer requirement saves space, and the examples provided make the transition really smooth.

Pros

  • Support for all screens
  • Large choice of sizes
  • Deep black and red colours

Cons

  • Almost all pins used
  • ​Built-in Flash memory not used in standard libraries

Wrap-Up

  • Deep black and red colours
  • Large choice of sizes
  • Improved speed and readability

Links
Posted: 15 Nov 2018
Updated: 07 May 2019