A few questions about teensy 3.6 , leds , and ethernet

[visualSound]

Hi everyone!

I've been off this forum for a couple years and right now I'm just getting my self up to speed about the 3.6 and it's led driving capabilities - I've used the 3.2 heavily until the last couple years with the octo adapter board etc and had great results but hit a pretty consistent bottleneck of 3200 pixels per teensy3.2 (streaming pixel data via usb) and about 3-4 teensys per usb card/group

I just wanted to get clarification on some things I've been reading if possible!

1) I'm reading that the 3.6 has 32 dma channels - can we use more than 8 to drive ws2811/12b style strips in parallel now?
https://www.pjrc.com/teensy/techspecs.html

1a) If so, is this as simple(doubtful!) as declaring more dma friendly pins somewhere in the code?
1b) If not, what changes need to happen and where, generally speaking? Is it just a complicated feature to add?
I'm aware of fastLED and it's bit banging approach to surpass 8 but looking at dma based options only.

NOTE: I realize that the suggestion people usually have is if you can afford that many pixels just buy another teensy. True!
However I'm looking to understand the new limitations and I also see value in using many short strips vs fewer longer strips in quite a few situations.

2) Can the faster 480mb "Usb1" be used instead of the standard 12mb "Usb0" to stream say led data to the teensy faster?
Ultimately, my reason for asking - if we can push data to the teensy faster can we have more teensy 3.6's connected to a single multi-tt hub at similar frame rates?

3) What's the recommended model/type RJ45 breakout for maximum data streaming / throughput currently?
I've used the wiz820io before, and I'm hearing a bit about the wiz850io but what's the latest and greatest recommendation here?

Appreciate your time - thanks.
Lucas

 

[Epyon]

3) What's the recommended model/type RJ45 breakout for maximum data streaming / throughput currently?
I've used the wiz820io before, and I'm hearing a bit about the wiz850io but what's the latest and greatest recommendation here?

Both perform the same and are pin and library compatible. The 850io is based on the W5500 however, which is a production optimised version of the W5200 found in the 820io. It's cheaper and consumes somewhat less power, so for your wallet this would be the recommendation.

You can buy Wiz850io clones from China for less than €/$10. They are actually legit devices because they use the original W5500. I've written a short comparison/experience with them here if you're interested.

 

[visualSound]

Hi Epyon,
Thanks for the reply!
This helps a lot.

I've found this data sheet/page on the w5500:
http://www.wiznet.io/product-item/w5500/

I'm reading this:

The W5500 SPI supports 80 MHz speed and the new efficient SPI protocol, so users can implement high speed network communication.

Am I correct to assume this translates into 80 mbps aka 12.5 Mb/s? I imagine the teensy 3.6 would not be a bottleneck here assuming all I want to do is take the bytes and put them straight on the leds more or less?

Also reading this interesting bit:

It is possible to use 8 independent hardware sockets simultaneously.

Does this mean anything to users? Or does this happen automatically or not meaningful to teensy users at all?

Thanks again
Lucas

 

[Epyon]

The W5xxx can receive at link speed (+/-80Mbps) if you send short UDP bursts to it that fit within the internal 32kB RAM buffer. The SPI bus on T3.x only runs at 24-72MHz though. It will probably require some low-level SPI code as well, the default Ethernet library leaves a lot to be optimised.

The default number of sockets in the Ethernet library is 4, so that's 8kB per socket if you use the standard library. You can change the number of sockets from 1 to 8 in the w5100.h file.

Best to search the forum for more information, e.g. in this thread.

 

[visualSound]

Epyon,
Thanks for the additional information.

I'll research more via that link and other places.
Sounds like 24 mhz low end aka 3 megabytes/s? That's quite a few leds and more than I think would be necessary for 1 teensy.

If anyone has more info on potential support for the additional dma channels or the massively increased data rate of the "usb1" host pins on top... Would be entirely grateful for any info people could provide.

Thanks!