Limit Switch Board (LIM)

Reports the state of two limit switches on the CAN bus. Firmware lives in src/lim.

This is the simplest board in the tree. It exists for places that need limit switches without a motor controller attached to read them. The mast limit is the current user.

Hardware

Interface	Peripheral	Notes
Limit switches A and B	GPIO	presence and polarity are configurable
CAN	FDCAN1
Logging	LPUART1 (DMA)

Behavior

Timer	Rate	Purpose
`htim6`	10 Hz	publish `LIMState`

There is no state machine and nothing to calibrate. The board reads both pins and publishes them on a fixed cadence. Configuration decides whether each switch is present at all, whether it is enabled, and whether it reads active high or active low.

CAN Interface

Receives

Message	Base ID	DLC	Signals
`LIMResetCmd`	`0x80310000`	1	`reset`, `clear_faults`
`ESWConfigCmd`	`0x80F00000`	6	`address`, `value`, `apply`
`ESWProbe`	`0x80F10000`	4	`data`

Sends

Message	Base ID	DLC	Signals
`LIMState`	`0x80300000`	1	`lim_a` (1), `lim_b` (1)
`ESWAck`	`0x80F20000`	4	`data`

Configuration

Definition: config/lim.yaml, 8 bytes, the smallest in the tree. Device values live under rover/cm/, for example rover/cm/mast_limit.yaml.

Register	Type	Meaning
`can_id`	`uint8`	this board's CAN node ID
`host_can_id`	`uint8`	where to address published state
`sys_cfg`	`uint8`	`lim_a_present` (bit 0), `lim_b_present` (bit 1)
`limit_cfg`	`uint8`	`lim_a_en` (0), `lim_a_active_high` (1), `lim_b_en` (2), `lim_b_active_high` (3)
`publish_frequency`	`float32`	CAN publish rate, Hz

See Register Definitions and CAN Configuration Interface.

Warning

publish_frequency is not currently read by the firmware. The transmit rate is whatever htim6 is set to in the .ioc, currently 10 Hz. Writing this register has no effect.

Building

./scripts/build.sh --src src/lim --preset Debug
./scripts/build.sh --src src/lim --preset Debug --flash

Warning

src/lim is not in ci.json, so it is not built by CI. Build it locally before pushing.