Add KiCad 9 schematic, project libraries and datasheetsHEADmaster

Schematic (kicad/), one sheet per function as on ULX3S:
  - power: TLV62569 bucks for +1V1 / +3V3, AP2112K LDO for +2V5
  - usb: USB-C with PTC and TVS, CH347F for JTAG and UART
  - fpga_power, fpga_config, fpga_banks_01/23/67: ECP5 LFE5U-25F caBGA256
    (pin compatible with the 45F), quad SPI flash, 50 MHz CLOCK_50,
    ball assignment as in PINPLAN.md
  - ethernet: RTL8211F gigabit PHY, HR911130A RJ45, shield via 1M || 1nF 2kV
  - sdram: 32 MB W9825G6KH-6
  - hdmi: TMDS from the FPGA (LVCMOS33D), AC coupled, ESD protected
  - user_io: SW, KEY (debounced), LEDR, LEDG, HEX0-HEX3 with DE1 names
  - gpio: two DE1 compatible 2x20 headers (THDB-ADA on GPIO_0),
    Pmod A/B, ESD arrays
  - testpoints: bring-up pads, M3 mounting holes

All parts have LCSC numbers, MPN and manufacturer for JLCPCB assembly;
footprints are cross-checked against the EasyEDA data.

Libraries: ECP5 symbols generated from the Lattice pinout CSVs (kipart),
CH347F, RTL8211F, SM410561N symbols, HR911130A symbol and footprint from
KiCad library merge requests, generator scripts in lib/tools/.

Datasheets of all parts except resistors and capacitors in datasheets/
(manufacturer copyright, not covered by the project licenses).

1 files changed, 38 insertions, 1 deletions

diff --git a/README.md b/README.md
index 81f493b..5314a9a 100644
--- a/README.md
+++ b/README.md
@@ -39,8 +39,45 @@ The board must have expansion port possibilites at least for low
 speed extensions. With the ECP5 a 40GbE port is not possible as
 the fpga does not have serdes at 10 Gigabit.
 
+### Tools ###
+
+The design is made with KiCad 9. The KiCad project is in `kicad/`, see
+`kicad/README.md`. The scripts that generate the project symbol libraries
+need kipart (`pipx install kipart`). Footprints and symbols are cross-checked
+against the JLCPCB/LCSC (EasyEDA) data with easyeda2kicad
+(`pipx install easyeda2kicad`).
+
+Optional: the KiCad MCP server `kicad-mcp-pro` lets an AI assistant such as
+Claude Code work with the KiCad project. Install it with pipx:
+
+    sudo apt install pipx
+    pipx ensurepath          # then open a new terminal
+    pipx install kicad-mcp-pro
+
+The file `.mcp.json` in the repository root registers the server for this
+project, with `kicad/` as the project directory. Start Claude Code in the
+repository root so that `${PWD}` points there.
+
+### Reference designs ###
+
+eboard builds on ideas from two open ECP5 boards. No files are taken from
+them; they served as examples for the circuits. To look at them, clone them
+at the given commit (e.g. into `ext/`, which git ignores):
+
+| Design | Repository | Commit | Used as example for |
+|--------|------------|--------|---------------------|
+| ULX3S | <https://github.com/emard/ulx3s> | `6a92cec6` (2025-04-27) | one sheet per function, power supply (TLV62569), SDRAM, HDMI output with LVCMOS33D, GPIO without series resistors |
+| ButterStick | <https://github.com/butterstick-fpga/butterstick-hardware> | `0694ddf` (2023-09-19) | gigabit Ethernet (KSZ9031; eboard uses the RTL8211F), USB-C, FPGA core voltage |
+
+    git clone https://github.com/emard/ulx3s.git ext/ulx3s
+    git -C ext/ulx3s checkout 6a92cec6
+
 ### License ###
 
 The hardware design files are licensed under CERN-OHL-S-2.0. The
 software under GPL-3.0-or-later. All documents are licensed under
-CC-BY-SA-4.0.
\ No newline at end of file
+CC-BY-SA-4.0.
+
+Exception: the manufacturer datasheets in `datasheets/` are copyrighted by
+their manufacturers and are not covered by these licenses (see
+`datasheets/README.md`).
\ No newline at end of file