CPU & Watchdog API

CPU & Watchdog

The CPU abstraction layer exposes low-level primitives that don't fit into any of the other modules: the watchdog timer (fault recovery and periodic interrupt mode), blocking delays, and convenience helpers for board LEDs. All of these are implemented against the arch-specific HAL under arch/msp430/.

Headers: kernel/cpu/tiku_watchdog.h, kernel/cpu/tiku_common.h.

Watchdog Timer

Header: kernel/cpu/tiku_watchdog.h

The watchdog has two modes: watchdog mode resets the CPU if it isn't kicked within the configured interval (for fault recovery), while interval mode delivers a periodic interrupt that can be used as a lightweight clock source. Both the clock source (ACLK or SMCLK) and the divider (64, 512, 8192, 32768) are runtime-configurable.

Types

typedef enum {
    TIKU_WDT_MODE_WATCHDOG = 0,        /* Reset on timeout      */
    TIKU_WDT_MODE_INTERVAL = WDTTMSEL  /* Periodic interrupt    */
} tiku_wdt_mode_t;

typedef enum {
    TIKU_WDT_SRC_SMCLK = WDTSSEL__SMCLK,
    TIKU_WDT_SRC_ACLK  = WDTSSEL__ACLK
} tiku_wdt_clk_t;

typedef uint16_t tiku_wdt_interval_t;
/* Valid values: WDTIS__64, WDTIS__512, WDTIS__8192, WDTIS__32768 */

Functions

Function	Description
`tiku_watchdog_init()`	Initialize with default settings.
`tiku_watchdog_config(mode, clk, interval, start_held, kick_on_start)`	Configure with custom parameters.
`tiku_watchdog_kick()`	Kick (reset) to prevent a timeout.
`tiku_watchdog_pause()`	Pause the watchdog.
`tiku_watchdog_resume()`	Resume the watchdog.
`tiku_watchdog_resume_with_kick()`	Resume with an immediate kick.
`tiku_watchdog_off()`	Disable entirely.
`tiku_watchdog_mode_str()`	Returns `"watchdog"` or `"interval"`.
`tiku_watchdog_get_mode()`	Returns the current `tiku_wdt_mode_t`.
`tiku_watchdog_get_clk()`	Returns the current `tiku_wdt_clk_t`.
`tiku_watchdog_get_interval()`	Returns the current `tiku_wdt_interval_t`.

VFS Integration

The watchdog is exposed via the VFS under /sys/watchdog/ so it can be inspected and reconfigured from the shell without recompiling:

Path	Read	Write
`/sys/watchdog/mode`	`"watchdog"` or `"interval"`	`"watchdog"` or `"interval"`
`/sys/watchdog/clock`	`"aclk"` or `"smclk"`	`"aclk"` or `"smclk"`
`/sys/watchdog/interval`	`64`, `512`, `8192`, or `32768`	Same values (divider)
`/sys/watchdog/kick`	Not readable (returns -1)	Any write kicks the timer

All watchdog writes call tiku_watchdog_config() internally, preserving unchanged parameters and kicking the timer to avoid an immediate timeout.

Common Utilities

Header: kernel/cpu/tiku_common.h

Small helpers that don't deserve their own module. The LED functions are backward-compatible aliases for the newer indexed tiku_led_* API; use the indexed API for new code.

Functions

Function	Description
`tiku_common_delay_ms(ms)`	Blocking delay in milliseconds.
`tiku_common_led1_init()`	Initialize LED1 hardware.
`tiku_common_led2_init()`	Initialize LED2 hardware.
`tiku_common_led1_on()` / `led1_off()` / `led1_toggle()`	LED1 control.
`tiku_common_led2_on()` / `led2_off()` / `led2_toggle()`	LED2 control.

Indexed LED Interface

Header: interfaces/led/tiku_led.h

Board-independent, index-based LED API. The number of LEDs is set per board via TIKU_BOARD_LED_COUNT; the interface adapts automatically. This is the preferred API for new code — the tiku_common_led* helpers above are thin compatibility wrappers.

Functions

uint8_t tiku_led_count(void);      /* board LED count              */
void    tiku_led_init(uint8_t idx);  /* init LED idx (0-based)      */
void    tiku_led_on(uint8_t idx);
void    tiku_led_off(uint8_t idx);
void    tiku_led_toggle(uint8_t idx);
void    tiku_led_init_all(void);   /* init every board LED at once */

VFS nodes /dev/led0…/dev/ledN are created automatically for each board LED and support the same 0/1/t value protocol as the indexed API.