An ePaper screen for the Raspberry Pi Zero
Many moons ago, we took a look at the original, full-size PaPiRus HAT. Now it’s the turn of its smaller sibling, designed specifically for use with the Pi Zero. Unlike conventional displays, it uses electronic paper (ePaper) technology to render text and images, which can remain on screen without any power connection for many days before slowly fading. Obviously, this is ideal for saving battery power in a portable project, such as a smart conference badge. The display is high contrast and readable even in bright sunlight.
The full article can be found in The MagPi 57 and was written by Phil King.
Like its big brother, the PaPiRus Zero is supplied in two main parts: the pHAT board with pre-soldered female header, and the screen itself, which is very thin. Assembly involves inserting the screen’s mini ribbon cable into the connector at the side of the pHAT, then securing the screen to the board with the double-sided sticky pads supplied. We tested out the 2.0-inch Medium display with 200 × 96 pixels, but a Small 1.44-inch screen (128 × 96) is also available, along with a multi-screen pack containing both sizes.
With the unit assembled and mounted on a Pi Zero’s GPIO equipped with male header (not supplied), it’s time to install the software via a single Terminal command. A second command is required to set the correct screen size, then you’re ready to roll.
One of the installed folders contains a few Python code examples to get you started, including a temperature readout that makes use of the pHAT’s built-in LM75 temperature sensor. The Buttons example demonstrates the use of the pHAT’s five GPIO-connected buttons. Located along the top edge, they’re tiny but could prove useful for switching the info displayed. Other code examples include Conway’s game of life, which works well, and a digital clock. While some minor latency is noticeable as the numbers change on the latter, a ‘clear’ command can be used to wipe the display clean.
The Papirus Python library includes a write function to print text strings, which can be positioned and sized, although it’s not clear how to change the font. A draw function displays a one-bit (black and white) bitmap image – The MagPi logo looked really cool! Handily, the software will convert most image types automatically.
While not suitable for applications requiring a fast screen refresh, the PaPiRus Zero is ideal for saving battery power in portable projects. The ePaper display is very easy to read in all but the lowest light conditions, from any viewing angle, and features a decent 110 ppi pixel density.