The W5100S ethernet back-end now works end-to-end on real hardware: a complete,
correctly-checksummed UDP datagram (10.0.0.99:40000 -> 10.0.0.50:6464, 32-byte
payload) was transmitted by the FPGA-driven W5100S and captured on a PC, after a
full bidirectional ARP handshake.
Records the three W5100S-specific findings in CLAUDE.md (NETLCKR unlock, the
15-bit IDM address space putting the buffers at 0x4000/0x6000, and the 60.3 ms
reset-to-ready time), and notes that UDP unicast is the reliable bring-up path
while a 255.255.255.255 send sets SEND_OK without appearing on the wire.
w5100_udptest.py is the self-contained configure+send+readback probe that
isolated all of this.
Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Reverts the 0x8000/0xC000 change from 162dbf7, which was WRONG and actively
broke transmission. The W5100S datasheet pseudo-code quotes 0x8000 (TX) /
0xC000 (RX) for the memory blocks, but the PARALLEL/indirect (IDM) interface
only decodes a 15-bit offset. Bench-proven with an address-aliasing probe:
writing distinct values to each candidate base and reading them back showed
0xC000 and 0x4000 are the SAME cell (0xC000 & 0x7FFF == 0x4000) while 0x6000
holds its own value.
Consequence of the bad base: every payload byte written to 0x9800+i aliased
down onto 0x0000+i, landing on SHAR (0x09-0x0E) and SIPR (0x0F-0x12) and
overwriting them with the payload. The chip then transmitted frames with a
garbage source MAC/IP, which the peer NIC drops without counting -- the
"SEND_OK but rx_packets=0" symptom, and the bogus SIPR0 readback (0x50 was
literally payload byte 15, 'P').
The NETLCKR unlock from 9c4bc7a is a genuine W5100S requirement and stays.
Also:
- w5100_udptest.py: self-contained configure+send+readback probe (and the
address-aliasing probe that found this), reports over UART.
- scripts/build-flash.sh: sweep N seeds and flash the best (capture timing is
seed-dependent, so the sweep is mandatory).
- scripts/uart-console.py: interactive UART console, plus --send/--read
one-shot modes for scripting.
Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Roflin