Lock Control

Purpose

This module commands the KR-S79 lock opening input.

The lock itself remains powered by the battery pack. The firmware only drives the control stage connected to the lock SIG input.

The GPIO is configured directly with GPIO_OUTPUT_INACTIVE. The idle state is low to avoid accidental opening at startup or after flashing.

int lock_control_init(void);

int lock_control_open(void);

lock_control_init() configures D9 directly as an inactive GPIO output.
lock_control_init() never sends an unlock pulse.
lock_control_open() drives D9 high for 150 ms, then immediately returns it inactive with gpio_pin_set_dt(..., 0). The additional 50 ms compared with the original pulse gives the mechanical relay more time to pull in while limiting coil-on time and battery use.
All GPIO return codes used by the lock control path are logged.
No PWM is used.

The main loop collects numeric keypad input.

Codes are six digits long.
Up to 8 permanent and 20 temporary/one-time codes can be stored.
Codes are persisted through Zephyr settings with the NVS backend.
The development default code is 784512.
A valid six-digit entry triggers lock_control_open().
The PN532 reader triggers lock_control_open() after a valid stored tag UID is detected.
*, #, and B clear the current entry.
A valid six-digit entry triggers one long success beep before the opening pulse.
An invalid six-digit entry triggers three short close beeps and keeps the red LED on for 1 second.
The first keypad press starts one non-renewable 15-second NFC scan window, shown with the blue LED; later presses cannot extend the active window.
A valid NFC tag UID uses the same success beep and lock opening path as a valid keypad code.
The green LED stays on while the lock state feedback reports the lock open.
A short reminder beep is emitted every 2 seconds while the lock state feedback reports open.
Door state changes are reported over UART as Door opened and Door closed.
Each periodic reminder is reported over UART as Door open reminder beep.
LEDs stay off during startup and while the lock is closed.