rs485-modbuslisted

# RS485 Modbus RTU — Operation Skill Drives a USB-to-RS485 dongle as a Modbus RTU master via a bundled `modbus.py`. Pure pyserial + hand-rolled CRC — no `pymodbus`, no `mbpoll`. Two layers: **generic** (any port/slave/register) and **emst-core preset** (defaults baked in, version readout pretty-printed). ## When this skill applies - Bringing up Modbus on new hardware - Verifying a slave is alive (read VERSION / known input register) - Inspecting holding/input register values - Sending control commands to a Modbus slave - Diagnosing CRC errors, no-response timeouts, slave-address mismatches - Sanity-checking firmware UART/DMA RX path during emst-core bring-up If the user is sniffing traffic between an existing master/slave pair (passive bus tap), this skill does not yet do that — say so and stop. ## Hardware assumption USB-to-RS485 dongle with **automatic direction control** (most modern FT232/CH340-based "RS485 USB转串口" adapters). No DE/RE pin handling in software. If the user has a manual-DE adapter, this skill won't work — flag it. ## Bootstrap (first run on a new machine) ```bash bash "$HOME/.claude/skills/rs485-modbus/scripts/setup.sh" ``` Creates `$HOME/.claude/skills/rs485-modbus/.venv/` with `pyserial`. Idempotent. Run it again any time you see `ModuleNotFoundError: No module named 'serial'`. ## Tool invocation ```bash SKILL_DIR="$HOME/.claude/skills/rs485-modbus" PY="$SKILL_DIR/.venv/bin/python $SKILL_DIR/scripts/modbus.py" $PY <subcommand> [--preset emst-co