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Thread: WS2812E teensy4.1 logic level shifting

  1. #1

    WS2812E teensy4.1 logic level shifting

    I see that Paul S suggests not to use mosfet level shifters...

    Teensy LC has a 5V buffer chip built in, connected to pin 17. The best way to use this buffer is leave pin 17 unused by your program (the pin defaults to a low power disabled state), and connect the data signals from pin 24 (or any other supported pin) to pin 17. Then connect the WS2812 LEDs to the 5V signal output.

    For Teensy 3.x, a separate 5V buffer chip should be used. Unidirectional buffer chips like 74HCT245 and 74AHCT125 are best. Do NOT use these mosfet transistor level shifters. They are far too slow for WS2812 LED data.
    is this reccommendation only for teensy 3.x? I have used a BSS138 based board (https://www.sparkfun.com/products/12009) on my teensy 4.1 driving 300+ neopixels and it is working fine. Any suggestions before I commit to a PCB fabrication?

  2. #2
    Senior Member PaulS's Avatar
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    Quote Originally Posted by snowsh View Post
    is this reccommendation only for teensy 3.x?
    No, it also applies to Teensy 4.x. The issue is speed of a MOSFET level shifter.
    Your current batch of Neopixels may work fine now but a next batch may not.
    I have also read recommendations of lowering the pullup resistor values on the HV side of the FET on the BSS138-based Adafruit board to speed up the level shifter [faster signal edges].
    But I would go for a unidirectional buffer chip to be save...

    Paul

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