Multiple LED matrix panel controlled with UART? - Page 1
Forum section: electronics / projects

author: OgreVorbis
author_rank: Newbie
timestamp: January 10, 2023, 11:21:42 pm
content: I've recently gotten obsessed with LED matrix panels. I bought one 64 x 32 panel from Lumex and I LOVE the fact that it uses a UART interface to draw graphics. However, it is not even close to big enough for meI began looking at the options to control multiple panels and unfortunately, they all use either an ethernet interface and complex prefabbed software, WiFi, or a "U-Disk" (which is just a USB stick).I want the panel to update constantly programmatically. I'm a decent programmer, so I want an RS232 serial/UART interface that I can program with a PC or arduino.Maybe some of you might know of some controller hardware that would support this? If not, then I'm not fully against it being an ethernet connection to the controller as long as there is some open source library I can use to control the panels with my own software?In other words, I want maximum flexibility and not "Chang SunnySky Better Hope LED show" software

author: OgreVorbis
author_rank: Newbie
timestamp: January 12, 2023, 08:11:36 am
content: I can't even find a dedicated forum or community for large matrix panel arrays. How do people actually use these things? Where's the software? The best I can find is software dedicated for Christmas.There HAS to be someplace to discuss these things in more detail.

author: Psi
author_rank: Super Contributor
timestamp: January 12, 2023, 08:19:20 am
content: Yeah, many panels are just raw on/off RGB elements. Meaning you have to mix them yourself to get any colors.You can obviously just turn 2 or 3 on at once and get 8 different colors. So if that's all you want its fine on an 8bit arduino core like a mega328.But if you want more than that you have to do some PWM color mixing which is totally doable but the demands on it get higher the more bits you want. If you want a nice smooth color gradient and no flicker you need a fast CPU. STM32F4 at over 100mhz doing DMA are nice for this.Have a look at the sparkfun onehttps://www.sparkfun.com/products/14646there's probably a community around that. But its not UART it needs a MCU to do all the heavy lifting and color mixing.So yeah, panels like you got with a UART interface are going to be easier to work with. But the UART will have a speed limit so check data rates and see if you can send enough data over the uart to update the number of pixels you want to be do per second

author: jiarui
author_rank: Contributor
timestamp: January 12, 2023, 05:18:35 pm
content: I assume that these LED grids are made with WS2812B type of chips. The control protocol for these chips are pretty simple. You can build an serial interface with these chips using an ARDUINO, or other uCs.

author: bidrohini
author_rank: Regular Contributor
timestamp: January 13, 2023, 07:38:49 am
content: You can daisy chain multiple 64x32 LED matrix panels to make a bigger display. I think that is an easy option.

author: alexanderbrevig
author_rank: Frequent Contributor
timestamp: January 13, 2023, 08:11:48 am
content: I've had fun using FPGA to drive these. I'd say it's a good first real project, if you're not familiar with FPGAs. There's good resources online too

author: tooki
author_rank: Super Contributor
timestamp: January 13, 2023, 09:10:06 am
content: Quote from: jiarui on January 12, 2023, 05:18:35 pmNope. They’re generally “dumb” multiplexed arrays using 74HC595-style shift registers (usually a specialized Chinese variant made specifically for this application that can handle 20mA-per-output current). They use two lines each for red, green, and blue, and then some more for row selection. The standard is called HUB75 if you’re curious.Since these are intended for video walls, they’re normally driven by dedicated FPGA-based systems at very high clock rates, which is why they’re quite challenging to drive with microcontrollers (an Arduino Mega can drive a 64x32 matrix at just 4096 colors and a fairly low refresh rate; an Arduino Uno can’t drive them at all due to insufficient memory). When microcontrollers are used, it’s typically with more powerful ones with ample memory and CPU speed, but critically containing some kind of DMA interface to get the data out quickly. (For example, one implementation for the ESP32 uses the I2S interface controller.) The serial-driven one the OP has is likely based on an STM32 or ESP32.Matrices of addressable LEDs do exist, but they’re very significantly more expensive.