BDF

2 Articles

an RGB LED display showing expected arrival times of trams and buses sitting on a table

A Private View Of A Public Transport Sign

November 12, 2022 by 11 Comments

[Stefan Schüller] was a fan of the LED signs that display arrival information for the trams and buses in their city of Zürich. [Stefan] was having trouble finding a source to purchase the signs so, instead, decided to build one himself.

[Stefan] decided to recreate the 56×208 single color 2mm dot pitch display with an 128 x 64 P2 RGB LED screen respecting the same 2 mm pitch. The display is driven by an ESP32 DMA RGB LED matrix shield utilizing a HUB75 RGB LED matrix library, all being powered from a 5 V 4 A power supply.

In addition to driving the LED matrix display, the ESP32 polls Zürich’s public transportation API and then parses the XML for the relevant information. Since [Stefan] wanted to match the fonts as closely as possible,
he created a new font from scratch, including the bus and accessibility icons. The new font was encoded into a glyph bitmap distribution format (BDF) that was then converted to work with Adafruit’s GFX library, with [Stefan] creating a custom conversion tool, called bdf2adafruit, to do the last leg of the conversion.

Since the LED matrix had full color capability, [Stefan] decided to add a little extra flourish and color code the transportation lines with the official tram colors. All source code is available on his GitHub repository for the project, for those looking for more detail.

We’ve featured DIY builds of public transportation feeds before. With the ubiquity of low cost RGB LED displays and public APIs, hopefully we’ll see many more!

Little Printer Dispenses Short Stories

February 25, 2020 by 11 Comments

We know how it happens. You buy a fancy new label printer, thinking this is the answer to your disorganized space, but soon entropy grabs the printer as well, and it becomes just another item in the pile. When you find such items later, though, they can spark ideas. The idea that struck [Eric Nichols] was to turn his diminutive thermal printer into a dedicated one for short stories.

Inspired by an article about a vending machine that dispenses stories selected by the reader’s time constraints, [Eric] took on the task of getting his Dymo LabelWriter 400 Turbo working in this new capacity. The first task was finding some continuous roll paper that would fit, because the official stock for this thing is all labels. He got lucky on the first try and a roll of 2 7/16″ receipt paper fit the bill perfectly.

The printer itself doesn’t have much brains; it prints bitmaps 672 bits wide, and as long as you care to make them. While the initial experiments succeeded in printing graphics, [Eric] needed a way to convert his stories to bitmapped text to send to the printer. The human-readable font file format known as BDF (glyph Bitmap Distribution Format) was a perfect fit, since a library to render it was readily available. On top of that, the open-source tool otf2bdf will convert a TrueType (TTF) font to BDF, completing his font-rendering chain.

[Eric] has these printers working with both Linux and windows, either one running on a PC where his software resides, and has it all well-documented on his site. With this in place, it’s simply a matter of coming up with the stories to print. We think it would be perfect for Hackaday dailies!

We’ve seen interesting hacks with disused printers before, like this ascii-art generating cartridge.