Liteeth on GateMate #196
Description
First of all this looks awesome. There is nice documentation I can configure it however I want. It has 271 stars, and is used by the Litex framework. I trust that it works. And I know Python. Perfect.
It even runs on GateMate. Slide 17. So I linked to it from the "Open Source Video Pipelines Wiki".
Here are my comments.
You may want to put a link to the documentation at the top of the README.
My problem is that I do not (yet) understand enough about Ethernet phys and SerDes. I am a newbie to Litex, Migen and Ethernet, but do have a master's in EE Digital design. So some links to the relevant introductory documentation would be helpful. Here are some specific questions.
What are the different types of SerDes on all of those different supported platforms, and which one is closest to GateMate?
What voltages do the different ethernet phy's use?
The Liteeth documentation says that it goes up to 3.125Gbps. There is this issue about 5Gbps ehternet. The GateMate demo was at 1Gbps. The GateMate Serdes runs at least up to 5Gbps. The obvious question is will Liteeth go up to 5Gbps, in general, and on GateMate, and what would I need to do to make that happen?
How is the signal encoded on the analog wire?
Since ethernet has multiple nodes, they must have high impedance. but the GateMate SerDes uses LVDS which is driven by a current source across 100 Ohm resistor. So I am not sure how to hook the two together, but clearly it is possible. Maybe that is why it only ran at 1Gbps?
One more feedback. It would be helpful to see how many FPGA resources this consumes on different platforms. In my case, I just want to do UDP transmit of video data. Maybe UDP receive will come later.
Another interesting piece of information would be to compare this with the competing open source solutions.
Thank you so much for providing this.
Christopher Lozinski