ESP32-C3 + WS2816 issues

[mcer12]

First off, I'm sorry if this is the wrong place to discuss this.

In the Wiki -> ESP32 NeoMethods there are some limitations mentioned about C3 module but it should generally support I2S, RMT and bitbang but I wasn't able to use neither of those. Bitbang is working but unusable (glitches), RMT and I2S don't crash but don't do anythig. The only thing that works is the default NeoWs2816Method. Searching through issues, I2S seems to be unsupported but RMT should work... which it doesn't, at least for me. Maybe the documentation is correct but there's an issue with WS2816 implementation in particular? Tested on NeoPixelTest example.

[Makuna]

Its best to start these is the discussion area first. Once its know its a bug in the code, an issue could be created.

ESP32-S3 and ESP32-C3 do not support i2s yet. There is an issue tracking that already.

https://github.com/Makuna/NeoPixelBus/wiki/ESP32-NeoMethods does not correctly state this (it may by the time you read this though).

It helps if you provide the snippit of code that shows how you define your neopixelbus for each case.

NeoWs2816Method maps to RMT channel 1 on S2/C3/S3, so it if works then RMT works. It is the same as NeoEsp32Rmt1Ws2812xMethod.

[mcer12]

It's a custom board, here's how it looks. I maybe wasn't clear that the "flicker" only occurs with update as in random data is passed to the second half of the strip and stays that way until next update. Sometimes the update is successful without any glitches. I can make a video if that helps.

[Makuna]

BTW, i2S is not supported on C3 at all right now. So, I am unsure how you tried it as it should not have compiled if you used an i2s specific method name. The unspecific names like NeoWs2816Method uses RMT on C3 and S3.

You are using the latest version of the library, correct?

I believe I see the wider positive power bus, but where is the equally sized GND? Is it the rest of the surface (ground plane)? Backside? How does it get to the third row from the bottom as the signal wires isolate that plane? Again, Vias to the other side?

When you state it works fine with low levels of color Rgb48Color(10,10,10) and not with higher levels like Rgb48Color(5000,5000,5000) this indicates to me that it's a power distribution issue. Either too small of a power supply or poor GND/+ wire sizing. What about Rgb48Color(512,512,512)?

225 pixels => 60ma (@5v) x 225 = 13.5A. that's over 13 AMPs of power. This is max at full bright, so a worst-case scenario; but a good engineering practice is to provide more than you need by a small margin.

[mcer12]

@Makuna whole bottom side of the board is a GND plane. Please note that I'm using WS2816C which is a low current version (12mA per led max accoring to datasheet, that means about 2.7A max), power supply is 5A rated. There's also a 3A fuse onboard, which doesn't blow :)

[mcer12]

I am using latest ESP8266/ESP32 arduino packages as well as latest library. Yes I understand I2S isn't working for ESP32C3, I was using RMT method there.

[mcer12]

@Makuna I replaced and tested few leds that seemed they could be causing the glitching and it's solved! Full brightness, no glitches! So either they were faulty or there was some hidden cold joint (i did solder these by hand). What I don't understand is why it worked fine at low brightness but who cares. I'll keep it running for few hours, see if it's really not doing anything weird anymore and close the discussion. Thank you very much for your help and for insisting on it being a HW problem.

[Makuna]

Since I have a test case (you), would you be willing to try a small change for RMT to better fit the spec? I will put a formal branch, but you could just change NeoEsp32RmtSpeedWs2812x class in the NeoEsp32RmtMethod.h to test it.

Change the NeoEsp32RmtSpeedWs2812x class in the NeoEsp32RmtMethod.h to this

class NeoEsp32RmtSpeedWs2812x : public NeoEsp32RmtSpeedBase
{
public:
    const static DRAM_ATTR uint32_t RmtBit0 = Item32Val(260, 1000);
    const static DRAM_ATTR uint32_t RmtBit1 = Item32Val(660, 600);
    const static DRAM_ATTR uint16_t RmtDurationReset = FromNs(280000); // 280us

    static void IRAM_ATTR Translate(const void* src,
        rmt_item32_t* dest,
        size_t src_size,
        size_t wanted_num,
        size_t* translated_size,
        size_t* item_num);
};

Then give it a try and see if it still works.

[mcer12]

I'll try that but I'll have to first solder the C3 module back :) If you're wondering, ESP32-C3-WROOM-02 and ESP32-WROOM-02 are somewhat pin compatible. I'd leave the reset at 300us because the datasheet says >280us.

[Makuna]

The reset time in the structure is a minimum, at best it usually takes another 20us and at worst another 80us. All depends on byte boundaries from count and size of pixels and rounding up to size boundaries DMA requires. And a little code overhead.

AND note, you can use RMT for any ESP32 variant, it's the i2S that is limited to ESP32, C2, and S2.