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Thread: Renard serial outputs zeroes

  1. #1
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    Jan 2021
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    Default Renard serial outputs zeroes

    Hello.
    I'm currently struggling with Renard output. Occasionally, output frame contains zeroes in value bytes (protocol service bytes like sync and command are ok), which makes LEDs to flicker for a moment.
    I have encountered this trouble in v3.7u1, and in v3.7u4 it's still present.
    In my setup i use NRF52840 MCU with USB CDC in it, it parses output data internally and sends it via radio to device which outputs received data to LEDs. MCU enumerates as serial port in my system. Then this port is set in Renard display in Vixen. Display uses 381 channels.
    Seems like problem reproduction rate does not depend on baud rate or execution engine refresh rate (but with slower rate i get less frames overall, so i encounter less zero frames), nor it depends on display size, effects used or any other condition i thought of so far, and it happens as often during show playback as with effect preview.

    I've done some debugging in my device's firmware, it does not seem like it's USB stack or internal (in device firmware) Renard protocol parser are at fault here. I've also tried to redirect output to terminal viewer program via com0com driver and issue is reproducing there - i can see sometimes i get zero frames there as well.
    I can reply with data capture i've managed to get with realterm if someone needs it, but from what i can tell about it - zero frames just happen, without any kind of change in previous or next frames.

    I have also tried to set up display as Generic Serial with data header and footer but for some reason Vixen struggles with device's serial port. It does not open it properly, freezes on start/stop in display menu and no data flow happens, so i eventually went back to Renard since it is the only working option i have for now. Directing Generic Serial to software defined port (via com0com) and capture output in realterm seems to work okay and sending data to device from terminal program also works, so it seems like device USB CDC drivers are working properly and i'm not sure what causes Vixen to behave like it does, but i would like to focus on Renard for now.

    I have not tried to use other USB devices like USB-TTL converters, since i see that even COM port emulation encounters this same issue.

  2. #2
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    Default Re: Renard serial outputs zeroes

    Nevermind, seems to be able to reproduce it only during effect preview. Still not sure why, but show playback with "set value" effect for full show's length seem to not give blank frames anymore, which sort of fine for now.

  3. #3
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    Default Re: Renard serial outputs zeroes

    I'm glad you discovered that last bit. I'd never have guessed that's how you were testing it. The effect preview is not designed to be a seamless loop. It's really intended only for visualizing effects while testing things, not for show usage. What you're seeing here is behavior I'd expect to see.
    The output from the controllers is not connected to playback. The Vixen execution engine is always sampling the state of the elements and outputting regardless of whether you're playing something or not. So it's possible that the engine samples state one or more times during the interval between iterations of the effect preview loop. At those times the element state is actually null so the output correctly is sending zeros.

  4. #4
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    Default Re: Renard serial outputs zeroes

    Quote Originally Posted by jchuchla View Post
    The output from the controllers is not connected to playback. The Vixen execution engine is always sampling the state of the elements and outputting regardless of whether you're playing something or not. So it's possible that the engine samples state one or more times during the interval between iterations of the effect preview loop. At those times the element state is actually null so the output correctly is sending zeros.
    Oh i think i get it know why it's expected behavior. Thanks!

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