51c4fb1089
A C framework for commanding a Pico WH robot over USB, WiFi or BLE with a
small text DSL. No hardware attached yet, so the whole stack runs on the
host against a simulated HAL and is covered by tests.
Two specifications drive the code:
docs/grammar.md the language — one namespace of callables (native,
firmware-resident, and defined over the wire), procedures
with named arguments and defaults, REPEAT, and the rules
that keep it safe on a microcontroller.
docs/flow.md transport, bracket-balance framing, the envelope,
admission, execution, abort and failsafe.
Three properties the design leans on:
- Bodies may only reference callables that already exist, so the call
graph is acyclic by construction, recursion is unrepresentable, and
interpreter depth is checked at definition time rather than discovered
at runtime.
- Nothing blocks. The interpreter is a resumable state machine over an
explicit frame stack, so ABORT is honoured within one tick even in the
middle of a long move, and no program can overflow the MCU stack.
- No queue. One outstanding statement at a time, which keeps abort to a
single unambiguous victim and avoids inventing an answer to "the
running program failed, does the queued one still go?".
Named arguments are resolved to the callee's parameter order at definition
time, so they cost nothing at execution.
rubo_core is target-independent. Porting to the Pico means providing a
non-blocking rubo_transport_t and a rubo_hal_t, and nothing else.
Not built yet: the Pico transport and HAL, the camera DAT/DEND bulk path,
and IF/ELIF, which is reserved in the grammar and lands with the sensors.
Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01Hfu1EFVbpee92zvzQunsKb
rubo
A C framework for commanding a small robot — Raspberry Pi Pico WH, two motors driving four wheels, a black-and-white camera — over USB, WiFi or BLE, using a small command language.
The hardware isn't attached yet, so the whole stack runs on the host against a simulated HAL. The language, the framer and the interpreter are exercised by tests with no Pico in the loop.
Specifications
| Document | Covers |
|---|---|
docs/grammar.md |
the language: callables, procedures, named arguments, REPEAT, the rules that keep it safe |
docs/flow.md |
transport, framing, the envelope, admission, execution, abort and failsafe |
Read those before changing anything here. Most of what looks like an odd decision in the code is a decision recorded in one of them.
Build and test
cmake -S . -B build
cmake --build build
./build/test_rubo # or: ctest --test-dir build
Drive it
./build/rubo_host --trace
--trace prints motor state changes. Try:
PING
STAT
SQUARE side=400
DEF ZIGZAG $deg=20 $reps=3 [
REPEAT $reps [
TURN dir=LEFT deg=$deg;
TURN dir=RIGHT deg=$deg
]
]
ZIGZAG deg=15
ABORT
--script makes it read piped input as a well-behaved client would: one
outstanding statement at a time, waiting for DONE or ERR before sending
the next (docs/flow.md §9).
./build/rubo_host --script < commands.txt
Layout
include/rubo/rubo.h public interface: limits, error codes, framer, engine
include/rubo/hal_sim.h simulated hardware, host only
src/lexer.c tokeniser (grammar.md §3)
src/parser.c recursive descent, validation (grammar.md §4, §5)
src/registry.c callable table and arena (grammar.md §2)
src/sym.c identifier interning
src/exec.c resumable interpreter (flow.md §8)
src/framer.c bracket-balance framing (flow.md §4)
src/session.c envelope and admission (flow.md §5, §7, §9)
src/natives.c built-in callables (grammar.md §8)
src/stdlib.c firmware procedures, in the language itself
src/hal_sim.c simulated motors and camera
host/main.c the main loop from flow.md §8.3
host/transport_stdio.c non-blocking stdio transport
tests/test_rubo.c host tests
Porting to the Pico
Two things, and nothing else:
- a
rubo_transport_tover USB CDC, lwIP or BLE NUS —read()must never block; - a
rubo_hal_tdriving the real motors.
rubo_core is target-independent and does not change. That is the point of
the layering in docs/flow.md §2, and it is why the language is testable
today.
Status
Working: the language end to end (definition, named arguments, defaults,
REPEAT, procedures calling procedures), framing, the envelope, admission,
abort, the deadman, and a simulated HAL.
Not built yet: the Pico transport and HAL, the camera DAT/DEND bulk path
(docs/flow.md §11), and IF/ELIF, which is reserved in the grammar and
lands with the sensor layer (docs/grammar.md §7).