/**
 * @file fhss.h
 * @brief FHSS channel sequencer based on AES-128-ECB.
 *
 * Both link endpoints derive the same hopping sequence independently from a
 * shared 128-bit key and a monotonically increasing slot counter.  No
 * synchronisation traffic is required as long as both sides start from the
 * same slot.
 */
#pragma once
#include <stdint.h>

/** @brief Reset the slot counter to zero. */
void fhss_init(void);

/**
 * @brief Return the next channel in the hopping sequence.
 *
 * Encrypts the current slot counter big-endian with AES-128-ECB, returns
 * @c block[0] % 40, and advances the slot counter.
 *
 * @return Channel index in [0, 39].
 */
uint8_t fhss_next_channel(void);

/** @brief Advance the slot counter without transmitting (receiver side). */
void fhss_sync_tick(void);