Signal map

The SignalId enum is the integer key into SignalStore. Every signal the firmware understands has a stable id; the on-disk signals.json maps frame bytes onto these ids.

Adding a new signal: bump the enum in canshift-firmware/include/signal_map.h, add the name → id row in canshift-firmware/src/can/signal_map.cpp::kNameToId, mirror the entry in the Rust crate (rust/signal-map/src/lib.rs), and add the visual mapping in canshift-core. Source of truth across both languages — Unity tests pin the ids; cargo tests pin them on the Rust side.

Engine

id	Name	Unit	Source
0	rpm	RPM	broadcast or OBD-II mode 01 PID 0C
1	throttle_pos	%	OBD-II PID 11
2	map_kpa	kPa	OBD-II PID 0B
3	boost_bar	bar	derived / broadcast
4	iat_c	°C	OBD-II PID 0F

Temperatures

id	Name	Unit	Source
5	coolant_temp_c	°C	OBD-II PID 05
6	oil_temp_c	°C	broadcast

Pressures

id	Name	Unit	Source
7	oil_press_bar	bar	broadcast
8	fuel_press_bar	bar	broadcast

Fuelling

id	Name	Unit	Source
9	lambda_1	λ	wideband O₂
10	afr_1	AFR	derived from lambda_1 × stoichiometry

Vehicle

id	Name	Unit	Source
11	speed_kph	km/h	OBD-II PID 0D
12	gear	(number)	broadcast

Electrical

id	Name	Unit	Source
13	battery_volts	V	OBD-II PID 42

ECU status flags

id	Name	Source
20	flag_mil	MIL bit on the OBD-II status frame
21	flag_launch_ctrl	broadcast
22	flag_flat_shift	broadcast
23	flag_anti_lag	broadcast
24	flag_traction_cut	broadcast

Map / profile

id	Name	Source
30	map_number	broadcast
31	map_name_idx	broadcast

Lap timer

id	Name	Unit	Source
40	lap_timer_ms	ms	broadcast or canshift-mobile push

Numeric gaps

The gaps (15..19, 25..29, 32..39, 41..63) are intentional — they reserve room for future signals in each semantic band without renumbering existing ids. SIGNAL_COUNT = 64 is the sentinel for unknown name.

Signal lifecycle

Every signal goes through SignalStore, which holds the latest raw value, an EMA-smoothed value, a last-update timestamp, and a valid flag. The store invalidates entries older than SIGNAL_DEFAULT_TIMEOUT_MS = 1000 (default; per-signal override in signals.json).

Details in SignalStore.