HackSpace magazine

Bluetooth 'cat' thermal printer review

By Jo Hinchliffe. Posted

Thermal printers have been the go-to technology for small, cheap, low-resolution yet reliable printing, till receipts being the most obvious use and, in years gone by, desktop calculators. It was perhaps the fact that thermal printers became available, back in the day, as a Game Boy accessory that piqued the interest of a generation of hardware hackers. Cut to today, and there are lots of stand-alone thermal printers that are available to connect to all kinds of devices for us to tinker with.

At the budget end of this market are very cheap, Bluetooth-enabled thermal printers which don’t appear to have a technical model number or company name. Rather, they are referred to as the animal depicted on the plastic enclosure. We opted for the ‘cat’ thermal printer, which arrived well-packed with a roll of paper for £16.

The printer has an internal battery, which needs charging via a micro USB cable (included). Once charged, a single button press (there is only one button) turns the unit on. Double-pressing the button causes the printer to print a test page that features a QR code and some details, including the device Bluetooth name and the pairing PIN.

Trying to scan the QR code the printer created, our Android phone failed to read it. We presumed that the QR code would be linking to an app for installation, so this left us scratching our heads as to how to use the printer. A quick search online revealed that we were not the only ones to have this issue, and we discovered that the app we needed to install was the ‘WalkPrint’ app available on Google Play.

Using the pairing PIN provided, we connected to the printer with ease and launched the application. The application is full of flaws and typos, but functionally works to allow you to send images and text to the printer. It has a range of features, including various note-taking and list-making sections where you can add text over preset list designs. There are stacks of randomly collated areas in the app full of sticker designs and anime characters, and more. Of course, you can also just send an image or photo from your device to the printer. We also found that the ‘Banner’ section of the app allows you to create longer prints with oversized text – while this worked well, we were unsure which occasion calls for a tiny, cheaply printed banner, but never say never! 

We couldn’t work out a way to share text from other apps to the WalkPrint app, but we did find that the usual copy and paste Android functions for text worked well, allowing you to copy text from elsewhere into a new note. It’s possible, within a WalkPrint ‘note’, to add text, clip art images, and photographs and arrange them in the print area. While you probably aren’t going to publish a book on it, it’s fun to play with and works well. You can also save print jobs as native files within WalkPrint, so you can store a commonly used image or template in the app itself. Handy if you wanted to do print-on-demand contact slips at an event, for example.

We noticed an issue in that our usual preference is to have our phone running in dark mode – a black background with white text – as the normal state. In the app, this meant that everything printed as such, with a dark background; however, flipping to light mode temporarily when using the app rectified this problem.

Swapping rolls of paper is straightforward – simply press a large button on the side, and the front of the printer pops open, revealing the roll area. The roll sits inside with the paper fed out through the opening, and the pressure of the print head rollers pulls the paper through when printing. The rolls of paper are 57 mm wide and 30 mm in diameter – these are widely available; there are also sticker material rolls available in this size.

It’s quite fun to be able to print out and share images on the go, and also occasionally useful to share a note or print a to-do list. We imagine those who are into creating scrap-books or journaling might find this a useful and fun printer, as it stands, with no modification. However, researching this particular printer reveals that there are numerous projects and repositories where people have got this little printer hooked up to other microcontrollers. If you are an Arduino IDE user, then Larry Bank has created an incredibly useful library – this means that an Arduino or perhaps an ESP32 thermal printer project is well within reach. We were also interested to see that Adafruit has a tutorial by Jeff Epler looking at driving this very printer with CircuitPython using the Adafruit CLUE platform. As the CLUE platform is running CircuitPython, it’s probably only a hop and a skip away from getting this printer up and running with a Raspberry Pi Pico.

All in all, a lot of tech to play with on a lot of levels for not very much money.

Verdict

8/10

As it is, it prints reliably, albeit with a slightly clunky Android application – as a platform for projects, it’s a great piece of kit.

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