WS2811 vs WS2821  - Page 1
Forum section: electronics / beginners

author: made2hack
author_rank: Frequent Contributor
timestamp: June 22, 2015, 04:59:09 pm
content: Hello,So I am contemplating purchasing RGB "pixel" LEDs from WorldSemi and wondering about the difference between the WS2812 and WS2822 chips. The LED's are WS2812 and WS2822, however, the IC's contained in the LED chips are the WS2811 and WS2821, thus the title. I've attached (hopefully) the PDFs in this post as they did not seem to have them online.Basically, I need help decoding the Chinglish in these documents. One seems to be serial programmed and the other parallel? I'm not sure, but this is what I gathered since the WS2821 states "Parallel-Single" wire - Three channels. And, reading WorldSemi's Alibaba page states the WS2821 is also DMX512 protocol ready? OK.So, my question is - Which ones to get?What I mean is, I want to drive them with an MSP430 (specifically the MSP430G2553 - 16Mhz / 16Kb). How do I know which chips are better suited? How do I calculate how many of them I can run and how fast? I tried to read and understabd the chinglish data sheets but it all comes out as gibberish.QuoteWhat does this even mean? Can the MSP430 even address these chips? How fast? How do I translate 16Mhz into Frames per second x String of LED chips I can program? Should I even bother or go to a more powerful arm based platform like the Pi?Thanks in advance and I hope the question was clear.

author: miceuz
author_rank: Frequent Contributor
timestamp: June 22, 2015, 05:13:11 pm
content: Those are LED driver ICs you are refering to. I'd get WS2812B - controller chip is integrated near RGB led itself, easy to drive, plenty of example code around. You send serial data (24 bits per led) by providing different length pulses - longer for '1' and shorter for '0'. Each led "takes" first 24 bits it sees and passes the rest thru. When it sees data line low longer than ~50ms, it latches the data it has to the output.The best way to drive them is to use a microcontroller with DMA capability as is done in Fadecandyhttps://github.com/scanlime/fadecandyproject otherwise it's quite processor - intensive.

author: Kjelt
author_rank: Super Contributor
timestamp: June 22, 2015, 05:17:16 pm
content: if you look at the protocol those WS leds are not fun.I'd pass on them and look for RGB leds with seperate clock and datalines such as the apa102, at least you are in control wrt timing.

author: hneve
author_rank: Regular Contributor
timestamp: June 23, 2015, 07:41:54 am
content: What are you going to use them for.?It kinda depends on how much memory or communication is going to be going on. I have a few projects running the one data line from an 8mhz tiny85 with no problems but the code use almost no memory as the coloring is done mathematical. I belive you need something bigger if you have other plans.

author: Jeroen3
author_rank: Super Contributor
timestamp: June 23, 2015, 07:55:53 am
content: There are several other variants, not limited to worldsemi, which use a synchronous protocol. Which is much easier to implement.You can also consider using a special driver IC. Such as DM163. If your application supports the extra space required.

author: Tantalum
author_rank: Regular Contributor
timestamp: June 23, 2015, 10:43:40 am
content: Quote from: trs80 on June 22, 2015, 04:59:09 pmWell the RAM is the main limitation, the software implementation also of course.Don't worry you can easily go over 1000 chips per channel on small MCUs with the WS2812.Quote from: trs80 on June 22, 2015, 04:59:09 pmYou need, well, you have to use DMA (in conjunctions with timers/pwm signals), if you don't use DMAs to generated the datastream, the MCU will only be able to generate the signal and nothing else, otherwise he won't fulfill the timings restrictions.EDIT:The differences between WS2812 & WS2822S (WS2821 driver IC) are:- different communication protocol- WS2822S supports "only" 1024 chips max per channel- WS2822S strings are more reliable since those LEDs are connected in // (if one LED fails, the chain isn't broken)- WS2822S needs more external components (resistors)- WS2822S has 6 pins vs 4 pins for the WS2812, but is not as thick (1.6mm vs 2.0mm).No data found about brightness.

author: Kjelt
author_rank: Super Contributor
timestamp: June 23, 2015, 12:03:35 pm
content: Quote from: Jeroen3 on June 23, 2015, 07:55:53 amPlease do name them, always interesting to see whats out there

author: made2hack
author_rank: Frequent Contributor
timestamp: June 23, 2015, 12:33:34 pm
content: Well, basically I want to useGlediatoror other such software to have exciting visuals in large matrixes. Perhaps make squares or rectangles of 64 LEDs that can be daisy chained up to the maximum that your PSU can handle.Quote from: Kjelt on June 23, 2015, 12:03:35 pmI believe that Kjelt recommended the apa102 as an alternative and probably other chips with serial. Which, the more I look into it looks more reasonable.