What is it?

HT16K33 RAM mapping 16*8 LED driver (see data sheet) with four 4-digit, eight-segment HP QDSP-6064 LED displays

Why did you make it?

These HP QDSP-6064 bubble displays have a cool retro look right out of the seventies. More practically, they allow compact numerical displays and, coupled with the HT16K33 LED driver chip, 16 digits can be displayed with only two I2C wires, power and ground. That's a lot of display without taking up a lot of GPIO pins.

What makes it special?

There are a lot of advantages to this display design including 1) you don't need external current-limiting resistors with the HT16K33 chip, 2) you can run the display board with 3.3 V or 5 V as you wish, 3) it only takes four wires to control up to 8 x 4 four-digit displays since up to eight of these "FrontPacks" can be independently addressed in a given circuit by soldering a unique 3-bit address on the board pads, 4) it has a rather small footprint at 1.46 x 1.51 inches square so it saves space, and 5) it is so retro cool! For more discussion of how and why I designed this display, and an Arduino sketch with integer and floating point write routines for the bubble displays, see here.

Order the pc board from OSHPark.com and build one yourself, order the assembled display from me either with the four bubble displays ($25 plus shipping) or without the four bubble displays ($10). The bubble displays are the high cost item here; if you have some or can get some cheap, ordering the assembled board sans displays is the way to go! I got a good deal on bubble displays and I am able to lower the price of the Bubble Display FrontPack with four 4-digit QDSP-6064 bubble displays to $25. If you have your own or can get them cheap it is still a better deal to order the FrontPack sans bubble displays!

If you order with the bubble displays they will come mounted into the board thru-holes but unsoldered (the display works fine like this) since the other benefit of this design is that you can choose to mount the displays with up to a 20 degree tilt to aid viewing and can choose how high above the HT16K33 chip to set the displays to clear your case thickness, etc.