After lurking here for a while,

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(Thomas “Balu” Walter) #1

After lurking here for a while, I’m going to start my first project with an ESP32 and a 18x16 LED matrix plus 60 extra LEDs (based on WS2812b strips) - a “Word Clock” with a 60 LED ambient light border (or seconds display…).

From what I’ve read lately I should use the RMT driver on an ESP32 if I want to do Wifi and that supports 8 channels by default?

According to Mark Merlin amazing blog, I should even be able to receive IR signals too then (which uses one RMT channel?)?

I’m also thinking about adding an i2c RTC…

Since I have no experience with FastLED and it’s parallel output yet (or ESP32 for that matter :)), I wonder if the strips have to be of the same length.

Right now I am thinking of doing 4 channels each driving 4 rows a 18 LEDs (72 LEDs) for the main matrix plus 1 for the 60 LEDs for the ambilight. Having the strips in rows would make selecting the “words” easier. Total: 5 channels

Another option is rotate the strips 90 ° and do 6 channels with 3 columns a 16 LEDs (48 LEDs) each. Plus 1 channel for the 60 ambient LEDs as above. Total: 7 channels.

I think I’m going for the first because of the easier “word selection” (word starts at LED X and is Y LEDs long).

(Yves BAZIN) #2

@Thomas_Balu_Walter to drive a 18x16 matrix +60 leds, using parallel output is over kill with only one pin you will have a refresh rate of 95fps. My guess is that you will bother to much with wiring for not much of a useful gain. I would use two pins
One for the matrix and one for the 60 other leds.

(Thomas “Balu” Walter) #3

You are absolutely right, I have to be reminded sometimes[1] to not overengineer things… ;-). But one of the reasons for using multiple channels was to do exactly that - so I could learn how to do it in bigger setups. And since I’m using an 8 channel 74HC245 anyways, I felt it wouldn’t be that much of a hassle?

But yes, if I use two channels, I should be able to extend it later just the same…

[1] as in “always”

(Yves BAZIN) #4

@Thomas_Balu_Walter [1] we are all the same. If this build is the first step to something bigger then go for it ;). @Marc_MERLIN has indeed a great blog about using RMT channels for IR and using the FastLED library. And the esp32 is a great mcu. Can’t wait to see your build

(PaulStoffregen) #5

Don’t forget to buy the 74HCT245 chip. The extra “T” means it properly accepts 3.3V signals when running from 5V. The more common 74HC245 (without the “T”) is the same sort of input circuit as the LEDs - might work with 3.3V but not guaranteed. The letter “T” in the middle is the key detail to get right for converting 3.3V up to 5V.