(update, there is one:

(Marc MERLIN) #1

(update, there is one: https://www.tindie.com/products/jasoncoon/wemos-d32-esp32-led-level-shifter-shield/ https://www.tindie.com/products/jasoncoon/16-output-nodemcu-esp32-wifi-ble-led-controller/ )
@Jason_Coon I found your ESP32 shield with level shifter:
Good thinking, this was what I needed, except I needed this with 16 pins instead of 8.
Do you know if such a shield or would you be willing to consider one?

  1. 16 pin parallel output in ESP32 is what I use
  2. Talking to an RGBpanel also requires 16 pins
    Yeah, like you were, I’m using protoboards for now, not very nice, space efficient, or professional
(Marc MERLIN) #2

Never mind, you already did and I only found it now:

(Marc MERLIN) #3

But while I have you @Jason_Coon I noticed that you added some 500 Ohms resistors on your shield. Last I checked, those resistors are now folklore that was started by adafruit in their uberguide back in days when they were maybe needed on the very first neopixels.
I just bought 3 of your shields and m plan is to just bridge those contacts with solder. Any reason not to?
And did you find that the capacitors help (as in you added them after seeing issues), or you’re putting them just in case?

(Jeremy Spencer) #4

@Marc_MERLIN I just put together a quick Christmas installation with an ESP8266, some SK9822s and some 12v WS2811s. I used a level shifter but forgot to add the resistors on the output. The SK9822s we’re fine but the WS2811s had terrible flickering till I added a resistor in the data line, this fixed it :slight_smile: I did use 100ohm though

(Jeremy Spencer) #5

With flicker https://photos.app.goo.gl/AVMDSxC4rvTkAk6R8

(Jeremy Spencer) #6

With a resistor

(Lawrence Clark) #7

I use 5v leds with the nodemcu esp8266 without level shifting and it works fine …

(Marc MERLIN) #8

Thanks @Jeremy_Spencer , first time I see this (strips that need the resistor). Electrically, does anyone know what the resistor actually does? Doesn’t it lower the signal voltage back down somewhat, when usually the issue is that it’s not high enough to start with (unless you use a level shifter to bring it from 3.3V back up to 5V?)

(Marc MERLIN) #9

@Jason_Coon since you added those resistors to your shield, maybe you also has such an experience where they were needed?

(Thomas “Balu” Walter) #10

@Marc_MERLIN I was told that it dampens noise on the line, but I wondered if that’s true.

(Jeremy Spencer) #11

@Marc_MERLIN when I make up a level shifter, I always copy the octows2811 adapter, PJRC are much much better at designing circuits than me :wink:

(Jason Coon) #12

Hey, sorry I’m late to the thread. :slight_smile:

The small capacitors on my shields are decoupling capacitors recommended by the 74HCT245 datasheet to reduce high frequency noise that can adversely affect the high speed level shifters.

The resistors, in addition to supposedly protecting the LED data pins from current onrush (according to Adafruit), can also be used to match the data wire impedance. I usually use around 330 Ohm resistors. You can definitely try just bridging the connection.

The OctoWS2811 adaptor uses 100 Ohm resistors to match the impedance of Cat5/6 ethernet cable.

(Marc MERLIN) #13

@Jason_Coon ah, impedance, I keep forgetting about that, one of those pesky electronic reality things :slight_smile: I assume it doesn’t matter for short wire runs (<1m) but it probably does for longer ones. Thanks for explaining (and duly noted on the capacitors, been using my level shifters without them and I guess got lucky so far)

(Jason Coon) #14

@Lawrence_Clark yeah, you can definitely get by without a level shifter, it’ll often work just fine, until it doesn’t. Differences in power supply voltage, data wire length, etc, can make them necessary.

(Marc MERLIN) #15

@Jason_Coon I read the spec sheet of the level shifter and basically they recommend a 0.1uF capacitor between Gnd and Vcc to “clean up power”. Is that correct?

(Jason Coon) #16

@Marc_MERLIN yeah, as close to the level shifter as possible.

(Marc MERLIN) #17

Because I can’t paste, my edit was supposed to link to this https://www.tindie.com/products/jasoncoon/16-output-nodemcu-esp32-wifi-ble-led-controller/
This is the 16 way output one I’d recommend to anyone wanting to do massive parallel output on an ESP32 (or use SmartMatrix which requires a lot of output lines)