Crypt-Chat on DTEK‑V

RISC‑V firmware and tools for a UART‑over‑ESP8266 chat demo using a robust framed protocol (CRC16‑CCITT + byte stuffing). Includes a Python client for interacting over telnet.

Build

Prereqs:

• RISC‑V toolchain (riscv32-unknown-elf-*)
• dtekv-run and Intel jtagd

Commands:

• make (or make release) → build/main.bin
• make debug → no optimizations, with symbols
• make run → build + upload

Run the Client

Use the single protocol client:

python3 chat_client_protocol.py 192.168.4.1 [port]

Notes:

• Frame: [0xAA 0xAA][LEN][STUFFED_DATA]; unstuffed: [USER_ID][MESSAGE][CRC16] (CRC over USER_ID+MESSAGE)
• User IDs: 0x00 = board, 0x02 = client (default)
• Client drops frames with its own USER_ID

Source Layout

• src/boot.S — boot and trap handlers
• src/dtekv-lib.c — JTAG UART I/O, exceptions, interrupts, delay
• src/devices.c — LEDs, switches, button, 7‑seg, GPIO
• src/uart.c — bit‑banged UART: TX (busy‑wait + accurate timer), RX ISR + ring buffer
• src/chat_protocol.c — CRC16‑CCITT and byte stuffing
• src/chat_framer.c — frame collection state machine (+timeout)
• src/main.c — app glue: use framer, validate, echo; BTN1 sends message
• include/ — headers
• PROTOCOL.md — protocol details (concise)
• chat_client_protocol.py — Python telnet client (protocol)

Client tips:

• Set user id: --user-id 0x02 (default). Use --user-id 0x00 to act as board: send plaintext and let the board encrypt before echoing.