Homebrew 8-bit computers tend to have fairly limited displays, often one or more seven-segment displays and an array of LEDs to show the values of RAM or perhaps some other states of the computer. [Duncan] is in the process of building just such an computer, but wondered if there was a way to create a more visually appealing display while still keeping the computer true to its 8-bit roots. With some interesting TTL logic he was able to create this addressable RGB LED display to some remarkable results.
The array works by controlling the WS2812B LED strips with a specific timing cycle which was pioneered by [Tim] for a different project. [Tim] was able to perform this timing cycle with some simple Assembly code, which means that [Duncan] could convert that code into TTL gate logic relatively easily. Using 74LS02 NOR chips gets the job done as far as timing goes, and the pulses are then fed into a shift register and support logic which then creates the signal for the LED strips.
When everything is said and done, [Duncan] has a fully addressable 16×16 RGB LED array as a display for his 8-bit computer without violating any of his design principles and keeping everything to discrete TTL logic chips and a stick of RAM. It’s a unique method of display that might go along really well with any other homebrew computer like this one that’s also built with 74LS chips.
When we last heard from [lixielabs] he was building Nixie tube replacements out of etched acrylic and LEDs. Well he’s moved forward a few decades to bring us the Pixie, a chainable, addressable backpack for tiny LED matrix displays.
Each Pixie module is designed to host two gorgeous little Lite-On LTP-305G/HR 5×7 LED dot matrix displays, which we suspect have been impulse purchases in many a shopping cart. Along with the displays there is a small matrix controller and an ATTINY45 to expose a friendly electrical interface. Each module is designed to be mounted edge to edge and daisy chained out to 12 or more (with two displays each) for a flexible display any size you need. But to address the entire array only two control pins are required (data and clock).
[lixielabs] has done the legwork to make using those pins as easy as possible. He is careful to point out the importance of a good SDK and provides handy Arduino libraries for common microcontrollers and a reference implementation for the Raspberry Pi that should be easy to crib from to support new platforms. To go with that library support is superb documentation in the form of a datasheet (complete with dimensions and schematic!) and well stocked GitHub repo with examples and more.
To get a sense of their graphical capabilities, check out a video of 6 Pixie’s acting as a VU meter after the break. The Pixie looks like what you get when a hacker gets frustrated at reinventing LED dot matrix control for every project and decided to solve it once and for all. The design is clean, well documented, and extremely functional. We’re excited to see what comes next! Continue reading “A Tiny LED Matrix Is Better With Friends”
[Sean Hodgins] has a knack for coming up with simple solutions that can make a big difference, but this is one of those “Why didn’t I think of that?” things: addressable seven-segment LED displays.
[Sean]’s design is basically a merging of everyone’s favorite Neopixel RGB LED driver with the ubiquitous seven-segment display. The WS2811 addressable RGB driver chip doesn’t necessarily have to drive three different color LEDs – it can drive three segments of the same display. With three of the chips on a single board, all seven segments plus the decimal point of a display can be controlled over a single data line. No more shift registers, no more multiplexing. And as a nice touch, individual displays can be ganged together with connectors on the back of each module. [Sean] has some code to support the display but is looking for someone to build a standalone library for it, so you might want to pitch in. Yes, he plans to sell the boards in his shop, but as with all his projects, this one is open source and everything you need to build your own is up on GitHub. The brief video below shows a few daisy-chained displays in action.
Like many of [Sean]’s designs, including this Arduino rapid design board, this is a simple way to get a tedious job done, and it wrings a lot of functionality from a single IO pin.
Continue reading “Addressable 7-Segment Displays May Make Multiplexing A Thing Of The Past”
[Tim] discovered a simple way to measure the length of WS2812 addressable LED strips from a microcontroller. This is great for any project that can have an arbitrary length of addressable LED strip attached to it.
The simplest (and perhaps most reliable) way to measure strip length is by feeding the serial output pin of the end of the strip back to the microcontroller. The microcontroller keeps clocking bits into the strip until it receives data from the end of the strip. [Tim] didn’t want to run an additional signal to the end of his strip, so he found another solution.
[Tim] used the ADC of his microcontroller (an ATtiny) to measure supply voltage droop as LEDs are turned on. Each LED draws around 60mA at full brightness, so [Tim] sequentially turned on each LED and watched the ADC for slight voltage changes. If the voltage changed, there must be an LED at that address. [Tim] does note that this method is extremely dependent on the power supply used and only works on short strips. Check out his blog post for more details.
[Patrick] was prepping for some future projects he had in mind, for which he will need a simple 2D array of addressable LEDs. While it is certainly possible for him to build his own LED array and control hardware, he thought he would try out some off the shelf products to see if something might fit his needs.
He picked up a strip of addressable RGB LEDs from Adafruit, and while they worked very well, they were a bit too pricey for the amount of LEDs he knew he would need. He picked up a strip of similar LEDs without PWM capabilities built-in, and gave those a spin – they worked well enough, so he got to work building his LED array.
While LED strips might not jump right out as the best way to make an LED array, they can be easily cut and rearranged without any issue, provided you solder in a couple of wires to connect the disjointed strips. [Patrick] did just that, and wrote a small Arduino library that allows for easy control of the grid.
We’re not sure if he plans on scaling these arrays any larger than 8×8, but we are definitely interested to see what he has in store for them.
Check out a quick video of his LED array in action below.
Continue reading “Making A Simple Addressable Array From LED Strips”