Neil Matthews of Percheron Electronics, a long-time CamJammer, recently ran a Kickstarter to launch his first product: an E-paper HAT. He was kind enough to send me one for review and, now that Pi Wars is out of the way, I’ve managed to plug it in and have a play.
Features
The e-paper HAT display is 2.7″ diagonal and has a resolution of 264 x 176 pixels. In comparison to other displays, this does, of course, seem very low resolution, but then the usages for e-paper are very different to other displays. You aren’t going to be showing videos on this, but what it is great for is anything where you need information displayed on a low-power, infrequently updated device. The board has a real-time clock chip and battery (included) and also has space for 4 tiny buttons, useful for control on headless set-ups. Rounding off the features is a small RGB LED that can be used for a variety of purposes such as indicating the status of your internet connection (just off the top of my head).
The hardware
One thing you should bear in mind with this display is that it is fragile. No hardened skin like you’d get on a Kindle. This is okay as long as you know that. Putting the HAT on the Pi is easy enough, but one must be careful when detaching to pull it up by the circuit board, and not the screen.
The software
Installation of the software is very easy – you simply download a zip file, unzip it and run the install script. It takes a little while, with plenty of packages including I2C needed, so an ethernet connection is best. I did it over wi-fi though, had a cup of tea, and it was done, so no complaints there.
The scripts that you can then download from Github give you access to examples written in C and in Python. This is where a guide to the scripts and the API usage would come in handy, and there’s not much help for beginners. I don’t think the HAT is aimed at beginners, and so a bit of a hunt for what you want is probably okay, but I do think a little bit more time could have been spent hand-feeding people from first principles. It’s quite tough to understand some of the scripts, and some of that could’ve been hidden in a library. However, having said that, what is there is very good, very capable code. There are examples for displaying images, displaying a counter and even showing a full calendar clock, amongst others.
Documentation
As I’ve said, documentation could’ve done with some work, but there is a decent amount of stuff in README files on the Github.
Overall
This is a tough one to review. The hardware seems excellent to my untrained eye. It’s a tidy package, albeit with the warning about fragility. You certainly can’t dismiss the professionalism of the engineering on display. The software is good – actually quite comprehensive if you delve deep enough into it to understand it. The user experience, however, could do with some work. Perhaps a short manual to step you through getting it working and doing some simple examples, rather than just placing you at the mercy of demo scripts would be in order?
The price, at £45, is a little on the steep side but is comparable to the competition. The technology is pretty cutting edge, so you pay for it, I guess.
Overall, the Percheron Electronics e-paper HAT is a capable add-on board for the Pi and is ideal for low-power and low-frequency update purposes. I recommend it to anyone who has a purpose in mind for it and who wants to explore the options of e-paper technology.