/**
 * @brief Perform a single ED measurement
 *
 * @return ed_value Result of the measurement
 *         If the build switch TRX_REG_RAW_VALUE is defined, the transceiver's
 *         register value is returned.
 */
uint8_t tfa_ed_sample(void)
{
    trx_irq_reason_t trx_irq_cause;
    uint8_t ed_value;
    tal_trx_status_t trx_status;

    /* Make sure that receiver is switched on. */
    do
    {
        trx_status = set_trx_state(CMD_RX_ON);
    }
    while (trx_status != RX_ON);

    /*
     * Disable the transceiver interrupts to prevent frame reception
     * while performing ED scan.
     */
    pal_trx_bit_write(SR_RX_PDT_DIS, RX_DISABLE);

    /* Write dummy value to start measurement. */
    pal_trx_reg_write(RG_PHY_ED_LEVEL, 0xFF);

    /* Wait for ED measurement completion. */
    pal_timer_delay(TAL_CONVERT_SYMBOLS_TO_US(ED_SAMPLE_DURATION_SYM));
    do
    {
        trx_irq_cause = (trx_irq_reason_t)pal_trx_reg_read(RG_IRQ_STATUS);
    }
    while ((trx_irq_cause & TRX_IRQ_CCA_ED_READY) != TRX_IRQ_CCA_ED_READY);

    /* Read the ED Value. */
    ed_value = pal_trx_reg_read(RG_PHY_ED_LEVEL);

#ifndef TRX_REG_RAW_VALUE
    /*
     * Scale ED result.
     * Clip values to 0xFF if > -35dBm
     */
    if (ed_value > CLIP_VALUE_REG)
    {
        ed_value = 0xFF;
    }
    else
    {
        ed_value = (uint8_t)(((uint16_t)ed_value * 0xFF) / CLIP_VALUE_REG);
    }
#endif

    /* Clear IRQ register */
    pal_trx_reg_read(RG_IRQ_STATUS);
    /* Enable reception agian */
    pal_trx_bit_write(SR_RX_PDT_DIS, RX_ENABLE);
    /* Switch receiver off again */
    set_trx_state(CMD_TRX_OFF);

    return ed_value;
}

/**
 * @brief Switches the PLL on
 */
static void switch_pll_on(void)
{
    uint32_t start_time;
    uint32_t current_time;

    /* Check if trx is in TRX_OFF; only from PLL_ON the following procedure is applicable */
    if (pal_trx_bit_read(SR_TRX_STATUS) != TRX_OFF)
    {
        ASSERT("Switch PLL_ON failed, because trx is not in TRX_OFF" == 0);
        return;
    }

    /* Clear all pending trx interrupts */
    pal_trx_reg_read(RG_IRQ_STATUS);
    /* Get current IRQ mask */
    uint8_t trx_irq_mask = pal_trx_reg_read(RG_IRQ_MASK);
    /* Enable transceiver's PLL lock interrupt */
    pal_trx_reg_write(RG_IRQ_MASK, TRX_IRQ_0_PLL_LOCK);
    ENTER_TRX_REGION(); // Disable trx interrupt handling

    /* Switch PLL on */
    pal_trx_reg_write(RG_TRX_STATE, CMD_PLL_ON);
    pal_get_current_time(&start_time);

    /* Wait for transceiver interrupt: check for IRQ line */
    while (PAL_TRX_IRQ_HIGH() == false)
    {
        /* Handle errata "potential long PLL settling duration". */
        pal_get_current_time(&current_time);
        if (pal_sub_time_us(current_time, start_time) > PLL_LOCK_DURATION_MAX_US)
        {
            uint8_t reg_value;

            reg_value = pal_trx_reg_read(RG_PLL_CF);
            if (reg_value & 0x01)
            {
                reg_value &= 0xFE;
            }
            else
            {
                reg_value |= 0x01;
            }
            pal_trx_reg_write(RG_PLL_CF, reg_value);
            pal_get_current_time(&start_time);
        }
        /* Wait until trx line has been raised. */
    }

    /* Clear PLL lock interrupt at trx */
    pal_trx_reg_read(RG_IRQ_STATUS);
    /* Clear MCU's interrupt flag */
    pal_trx_irq_flag_clr();
    LEAVE_TRX_REGION();    // Enable trx interrupt handling again
    /* Restore transceiver's interrupt mask. */
    pal_trx_reg_write(RG_IRQ_MASK, trx_irq_mask);
}

/**
 * @brief Generates a 16-bit random number used as initial seed for srand()
 *
 * This function generates a 16-bit random number by means of using the
 * Random Number Generator from the transceiver.
 * The Random Number Generator generates 2-bit random values. These 2-bit
 * random values are concatenated to the required 16-bit random seed.
 *
 * The generated random 16-bit number is feed into function srand()
 * as initial seed.
 *
 * The transceiver state is initally set to RX_ON.
 * After the completion of the random seed generation, the
 * trancseiver is set to TRX_OFF.
 *
 * As a prerequisite the preamble detector must not be disabled.
 *
 * Also in case the function is called from a different state than TRX_OFF,
 * additional trx state handling is required, such as reading the original
 * value and restoring this state after finishing the sequence.
 * Since in our case the function is called from TRX_OFF, this is not required
 * here.
 */
void tal_generate_rand_seed(void)
{
    uint16_t seed = 0;
    uint8_t cur_random_val = 0;

    /* RPC could influence the randomness; therefore disable it here. */
    uint8_t previous_RPC_value = pal_trx_reg_read(RG_TRX_RPC);
    pal_trx_reg_write(RG_TRX_RPC, 0xC1);

    /*
     * We need to disable TRX IRQs while generating random values in RX_ON,
     * we do not want to receive frames at this point of time at all.
     */
    ENTER_TRX_REGION();

    /* Ensure that PLL has locked and receive mode is reached. */
    tal_trx_status_t trx_state;
    do
    {
        trx_state = set_trx_state(CMD_RX_ON);
    }
    while (trx_state != RX_ON);

    /* Ensure that register bit RX_PDT_DIS is set to 0. */
    pal_trx_bit_write(SR_RX_PDT_DIS, RX_ENABLE);

    /*
     * The 16-bit random value is generated from various 2-bit random values.
     */
    for (uint8_t i = 0; i < 8; i++)
    {
        /* Now we can safely read the 2-bit random number. */
        cur_random_val = pal_trx_bit_read(SR_RND_VALUE);
        seed = seed << 2;
        seed |= cur_random_val;
        PAL_WAIT_1_US();    // wait that the random value gets updated
    }

    set_trx_state(CMD_FORCE_TRX_OFF);

    /*
     * Now we need to clear potential pending TRX IRQs and
     * enable the TRX IRQs again.
     */
    pal_trx_reg_read(RG_IRQ_STATUS);
    pal_trx_irq_flag_clr();
    LEAVE_TRX_REGION();

    /* Set the seed for the random number generator. */
    srand(seed);

    /* Restore RPC settings. */
    pal_trx_reg_write(RG_TRX_RPC, previous_RPC_value);
}

static trx_retval_t trx_init(void)
{
	tal_trx_status_t trx_status;
	uint8_t poll_counter = 0;

	/* Ensure control lines have correct levels. */
	RST_HIGH();
	SLP_TR_LOW();

	/* Wait typical time. */
	DELAY_US(P_ON_TO_CLKM_AVAILABLE_TYP_US);

	/* Apply reset pulse */
	RST_LOW();
	DELAY_US(RST_PULSE_WIDTH_US);
	RST_HIGH();

	/* Verify that TRX_OFF can be written */
	do {
		/* Wait not more than max. value of TR1. */
		if (poll_counter == P_ON_TO_CLKM_ATTEMPTS) {
			return TRX_FAILURE;
		}
		/* Wait a short time interval. */
		DELAY_US(TRX_POLL_WAIT_TIME_US);
		poll_counter++;
		/* Check if AT86RF231 is connected; omit manufacturer id check */
	} while ((pal_trx_reg_read(RG_VERSION_NUM) != AT86RF231_VERSION_NUM) ||
			(pal_trx_reg_read(RG_PART_NUM) != AT86RF231_PART_NUM));

	/* Set trx to off mode */
	pal_trx_reg_write(RG_TRX_STATE, CMD_TRX_OFF);

	/* Verify that the trx has reached TRX_OFF. */
	poll_counter = 0;
	do {
		/* Wait a short time interval. */
		DELAY_US(TRX_POLL_WAIT_TIME_US);

		trx_status = (tal_trx_status_t) pal_trx_bit_read(SR_TRX_STATUS);

		/* Wait not more than max attempts for state transition */
		if (poll_counter == SLEEP_TO_TRX_OFF_ATTEMPTS) {
			return TRX_FAILURE;
		}
		poll_counter++;
	} while (trx_status != TRX_OFF);

	tal_trx_status = TRX_OFF;

	return TRX_SUCCESS;
}

/**
 * @brief Initializes the transceiver
 *
 * This function is called to initialize the transceiver.
 *
 * @return MAC_SUCCESS  if the transceiver state is changed to TRX_OFF and the
 *                 current device part number and version number are correct;
 *         FAILURE otherwise
 */
static retval_t trx_init(void)
{
    tal_trx_status_t trx_status;
    uint8_t poll_counter = 0;

    PAL_RST_HIGH();
    PAL_SLP_TR_LOW();

    /* Wait typical time of timer TR1. */
    pal_timer_delay(P_ON_TO_CLKM_AVAILABLE_TYP_US);

    /* Apply reset pulse */
    PAL_RST_LOW();
    pal_timer_delay(RST_PULSE_WIDTH_US);
    PAL_RST_HIGH();

#if !(defined FPGA_EMULATION)
    do
    {
        /* Wait not more than max. value of TR1. */
        if (poll_counter == P_ON_TO_CLKM_ATTEMPTS)
        {
            return FAILURE;
        }
        /* Wait a short time interval. */
        pal_timer_delay(TRX_POLL_WAIT_TIME_US);
        poll_counter++;
        /* Check if AT86RF233 is connected; omit manufacturer id check */
    }
    while (pal_trx_reg_read(RG_PART_NUM) != PART_NUM_AT86RF233);
#endif  /* !defined FPGA_EMULATION */

    /* Verify that TRX_OFF can be written */
    pal_trx_reg_write(RG_TRX_STATE, CMD_TRX_OFF);

    /* Verify that the trx has reached TRX_OFF. */
    poll_counter = 0;
    do
    {
        /* Wait a short time interval. */
        pal_timer_delay(TRX_POLL_WAIT_TIME_US);

        trx_status = (tal_trx_status_t)pal_trx_bit_read(SR_TRX_STATUS);

        /* Wait not more than max. value of TR15. */
        if (poll_counter == P_ON_TO_TRX_OFF_ATTEMPTS)
        {
#if (DEBUG > 0)
            pal_alert();
#endif
            return FAILURE;
        }
        poll_counter++;
    }
    while (trx_status != TRX_OFF);

    tal_trx_status = TRX_OFF;

    return MAC_SUCCESS;
}

/**
 * @brief ED Scan Interrupt
 *
 * This function handles an ED done interrupt from the transceiver.
 */
static void trx_ed_irq_handler_cb(void)
{
    uint8_t ed_value;

    /* Read the ED Value. */
    ed_value = pal_trx_reg_read(RG_PHY_ED_LEVEL);

    /*
     * Update the peak ED value received, if greater than the previously
     * read ED value.
     */
    if (ed_value > max_ed_level)
    {
        max_ed_level = ed_value;
    }

    /* Start next ED sampling */
    sampler_counter--;
    if (sampler_counter > 0)
    {
        // write dummy value to start measurement
        pal_trx_reg_write(RG_PHY_ED_LEVEL, 0xFF);
    }
    else
    {
        tal_state = TAL_ED_DONE;
    }
}

/**
 * Function initializing the Timestamp IRQ to get synchronized
 * as required for ranging.
 */
void rtb_tstamp_irq_init(void)
{	
    pal_trx_irq_dis();

    pal_trx_reg_read(RG_IRQ_STATUS);
    pal_trx_bit_write(SR_ARET_TX_TS_EN, 0x01);
    pal_trx_bit_write(SR_IRQ_2_EXT_EN, 0x01); //Enable Timestamping over DIG2 on the at86rf233

    PORTC.INTFLAGS = PORT_INT1IF_bm;

    TCC1_CTRLB &= ~TC1_CCAEN_bm;

    TIMER_SRC_DURING_TRX_AWAKE();

    PORTC.INT1MASK = PIN1_bm; //DIG2 over PortC 1

    /* Reset register, until time out is triggered is 65535 ms */
    TCC1_CNT = 0;

    PORTC.PIN1CTRL = PORT_ISC1_bm;

    TCC1_INTFLAGS = TC1_CCAIF_bm;

    TCC1_INTCTRLB = TC_CCAINTLVL_HI_gc;

    TCC1_CTRLB |= TC1_CCAEN_bm;	
}

/**
 * @brief Transceiver interrupt handler
 *
 * This function handles the transceiver generated interrupts.
 */
void trx_irq_handler_cb(void)
{
    trx_irq_reason_t trx_irq_cause;

    trx_irq_cause = (trx_irq_reason_t)pal_trx_reg_read(RG_IRQ_STATUS);

    if (trx_irq_cause & TRX_IRQ_TRX_END)
    {
        /*
         * TRX_END reason depends on if the trx is currently used for
         * transmission or reception.
         */
        if ((tal_state == TAL_TX_AUTO) || (tal_state == TAL_TX_BASIC))
        {
            /* Switch to transceiver's default state: switch receiver on. */
            set_trx_state(CMD_RX_AACK_ON);

            handle_tx_end_irq();            // see tal_tx.c
        }
        else   /* Other tal_state than TAL_TX_... */
        {
            /* Handle rx done interrupt. */
            handle_received_frame_irq();    // see tal_rx.c
        }
    }

}/* trx_irq_handler_cb() */

/**
 * @brief Switches the PLL on
 */
static void switch_pll_on(void)
{
    trx_irq_reason_t irq_status;
    uint32_t start_time, now;

    /* Check if trx is in TRX_OFF; only from PLL_ON the following procedure is applicable */
    if (pal_trx_bit_read(SR_TRX_STATUS) != TRX_OFF)
    {
        ASSERT("Switch PLL_ON failed, because trx is not in TRX_OFF" == 0);
        return;
    }

    /* use the IRQ status register checking for the actual PLL status */
    pal_trx_irq_dis();
    pal_trx_reg_write(RG_IRQ_MASK, TRX_IRQ_PLL_LOCK);  /* allow PLL lock IRQ only*/
    pal_trx_reg_read(RG_IRQ_STATUS);    /* clear PLL lock bit */

    /* Switch PLL on */
    pal_trx_reg_write(RG_TRX_STATE, CMD_PLL_ON);

    /* Check if PLL has been locked. */
    pal_get_current_time(&start_time);
    while (1)
    {
        irq_status = (trx_irq_reason_t)pal_trx_reg_read(RG_IRQ_STATUS);
        if (irq_status & TRX_IRQ_PLL_LOCK)
        {
            break;  // PLL is locked now
        }

        /* Check if polling needs too much time. */
        pal_get_current_time(&now);
        if (pal_sub_time_us(now, start_time) > (10 * PLL_LOCK_TIME_US))
        {
            /* leave poll loop and throw assertion */
#if (DEBUG > 0)
            ASSERT("PLL switch failed" == 0);
#endif
            break;
        }
    }
    pal_trx_irq_flag_clr();
    pal_trx_reg_write(RG_IRQ_MASK, TRX_IRQ_TRX_END); /* enable TRX_END interrupt */

    pal_trx_irq_en();
}

static void switch_rf_to_txprep(trx_id_t trx_id)
{
	uint16_t reg_offset = RF_BASE_ADDR_OFFSET * trx_id;
	pal_trx_reg_write(RF215_RF, reg_offset + RG_RF09_CMD, RF_TXPREP);
	/* Wait for TXPREP */
	rf_cmd_state_t state;
	do {
		state = (rf_cmd_state_t)pal_trx_reg_read(RF215_RF,
				reg_offset +
				RG_RF09_STATE);
	} while (state != RF_TXPREP);
	/* Clear TRXRDY interrupt */
	uint8_t irqs = pal_trx_reg_read(RF215_RF, trx_id + RG_RF09_IRQS);
	tal_rf_irqs[trx_id] |= irqs & ((uint8_t)(~((uint32_t)RF_IRQ_TRXRDY))); /*
	                                                                        * avoid
	                                                                        * Pa091 */
	pal_trx_irq_flag_clr(RF215_RF);
}

/**
 * @brief Subregister read
 *
 * @param addr Offset of the register
 * @param mask Bit mask of the subregister
 * @param pos  Bit position of the subregister
 *
 * @return  value of the read bit(s)
 */
uint8_t pal_trx_bit_read(uint8_t addr, uint8_t mask, uint8_t pos)
{
    uint8_t ret;

    ret = pal_trx_reg_read(addr);
    ret &= mask;
    ret >>= pos;

    return ret;
}

/*
 * \brief Starts ED Scan
 *
 * This function starts an ED Scan for the scan duration specified by the
 * MAC layer.
 *
 * \param scan_duration Specifies the ED scan duration in symbols
 *
 * \return MAC_SUCCESS - ED scan duration timer started successfully
 *         TAL_BUSY - TAL is busy servicing the previous request from MAC
 *         TAL_TRX_ASLEEP - Transceiver is currently sleeping
 *         FAILURE otherwise
 */
retval_t tal_ed_start(uint8_t scan_duration)
{
    /*
     * Check if the TAL is in idle state. Only in idle state it can
     * accept and ED request from the MAC.
     */
    if (TAL_IDLE != tal_state)
    {
        if (tal_trx_status == TRX_SLEEP)
        {
            return TAL_TRX_ASLEEP;
        }
        else
        {
            Assert("TAL is TAL_BUSY" == 0);
            return TAL_BUSY;
        }
    }

    /*
     * Disable the transceiver interrupts to prevent frame reception
     * while performing ED scan.
     */
    pal_trx_irq_dis();  /* Disable transceiver main interrupt. */
    set_trx_state(CMD_FORCE_PLL_ON);
    pal_trx_reg_read(RG_IRQ_STATUS);        /* Clear existing interrupts */
    pal_trx_bit_write(SR_RX_PDT_DIS, RX_DISABLE);
    pal_trx_irq_init((FUNC_PTR)trx_ed_irq_handler_cb);
    pal_trx_bit_write(SR_IRQ_MASK, TRX_IRQ_CCA_ED_READY); /* enable interrupt */
    pal_trx_irq_en();   /* Enable main transceiver interrupt. */

    /* Make sure that receiver is switched on. */
    if (set_trx_state(CMD_RX_ON) != RX_ON)
    {
        /* Restore previous configuration */
        pal_trx_bit_write(SR_RX_PDT_DIS, RX_ENABLE);
        pal_trx_irq_init((FUNC_PTR)trx_irq_handler_cb);
        pal_trx_reg_write(RG_IRQ_MASK, TRX_IRQ_DEFAULT); /* enable TRX_END interrupt */
        pal_trx_irq_en();   /* Enable main transceiver interrupt. */

        return FAILURE;
    }

    // write dummy value to start measurement
    pal_trx_reg_write(RG_PHY_ED_LEVEL, 0xFF);

    /* Perform ED in TAL_ED_RUNNING state. */
    tal_state = TAL_ED_RUNNING;

    max_ed_level = 0;   // reset max value

    sampler_counter = CALCULATE_SYMBOL_TIME_SCAN_DURATION(scan_duration) / ED_SAMPLE_DURATION_SYM;

    return MAC_SUCCESS;
}

/**
 * @brief Transceiver interrupt handler
 *
 * This function handles the transceiver generated interrupts.
 */
void trx_irq_handler_cb(void)
{
    trx_irq_reason_t trx_irq_cause;

    trx_irq_cause = (trx_irq_reason_t)pal_trx_reg_read(RG_IRQ_STATUS);

#if (defined BEACON_SUPPORT) || (defined ENABLE_TSTAMP)
#if (DISABLE_TSTAMP_IRQ == 1)
    if (trx_irq_cause & TRX_IRQ_2_RX_START)
    {
        /*
         * Get timestamp.
         *
         * In case Antenna diversity is used or the utilization of
         * the Timestamp IRQ is disabled, the timestamp needs to be read now
         * the "old-fashioned" way.
         *
         * The timestamping is generally only done for
         * beaconing networks or if timestamping is explicitly enabled.
         */
        pal_trx_read_timestamp(&tal_timestamp);
    }
#endif  /* #if (DISABLE_TSTAMP_IRQ == 1) */
#endif  /* #if (defined BEACON_SUPPORT) || (defined ENABLE_TSTAMP) */

    if (trx_irq_cause & TRX_IRQ_3_TRX_END)
    {
        /*
         * TRX_END reason depends on if the trx is currently used for
         * transmission or reception.
         */
#if ((MAC_START_REQUEST_CONFIRM == 1) && (defined BEACON_SUPPORT))
        if ((tal_state == TAL_TX_AUTO) || tal_beacon_transmission)
#else
        if (tal_state == TAL_TX_AUTO)
#endif
        {
            /* Get the result and push it to the queue. */
            if (trx_irq_cause & TRX_IRQ_6_TRX_UR)
            {
                handle_tx_end_irq(true);            // see tal_tx.c
            }
            else
            {
                handle_tx_end_irq(false);            // see tal_tx.c
            }
        }
        else   /* Other tal_state than TAL_TX_... */
        {
            /* Handle rx interrupt. */
            handle_received_frame_irq();    // see tal_rx.c
        }
    }
}/* trx_irq_handler_cb() */

/**
 * \brief Test the read and write of register on AT86RFx module
 *
 * This function will test the read and write functionalities of register
 * It will first write a known value (state) to register and reads the
 * register to confirm the same value.
 *
 * \param test Current test case.
 */
static void run_at86rfx_reg_access_test(const struct test_case *test)
{
	bool status;
	trx_cmd_t value;

	pal_trx_reg_write(RG_TRX_STATE, CMD_RX_ON);

	value = (trx_cmd_t) pal_trx_reg_read(RG_TRX_STATE);
	status = (CMD_RX_ON == value) ? true : false;
	test_assert_true(test, status == true,
			"Error Read/write AT86RFx register access failed");
}

/**
 * @brief Subregister write
 *
 * @param[in] reg_addr Offset of the register
 * @param[in] mask Bit mask of the subregister
 * @param[in] pos Bit position of the subregister
 * @param[out] new_value Data, which is muxed into the register
 */
void pal_trx_bit_write(uint8_t reg_addr, uint8_t mask, uint8_t pos, uint8_t new_value)
{
    uint8_t current_reg_value;

    current_reg_value = pal_trx_reg_read(reg_addr);
    current_reg_value &= (uint8_t)~(uint32_t)mask;  // Implicit casting required to avoid IAR Pa091.
    new_value <<= pos;
    new_value &= mask;
    new_value |= current_reg_value;

    pal_trx_reg_write(reg_addr, new_value);
}

/**
 * \brief ED Scan Interrupt
 * This function handles an ED done interrupt from the transceiver.
 *
 */
static void trx_ed_irq_handler_cb(void)
{
    uint8_t ed_value;
    trx_irq_reason_t trx_irq_cause;

    trx_irq_cause = (trx_irq_reason_t)pal_trx_reg_read(RG_IRQ_STATUS);

    if (trx_irq_cause & TRX_IRQ_CCA_ED_READY)
    {
        /* Read the ED Value. */
        ed_value = pal_trx_reg_read(RG_PHY_ED_LEVEL);

        /*
         * Update the peak ED value received, if greater than the previously
         * read ED value.
         */
        if (ed_value > max_ed_level)
        {
            max_ed_level = ed_value;
        }

        sampler_counter--;
        if (sampler_counter > 0)
        {
            // write dummy value to start measurement
            pal_trx_reg_write(RG_PHY_ED_LEVEL, 0xFF);
        }
        else
        {
            tal_state = TAL_ED_DONE;
        }
    }

#if (_DEBUG_ > 0)
    if (trx_irq_cause & (~(TRX_IRQ_PLL_LOCK | TRX_IRQ_CCA_ED_READY)))
    {
        Assert("Unexpected interrupt" == 0);
    }
#endif
}

/**
 * Function disabling the Timestamp IRQ as utilized for ranging.
 */
void rtb_tstamp_irq_exit(void)
{
    TCC1_INTCTRLB = TC_CCAINTLVL_OFF_gc;

    TCC1_CTRLB &= ~TC1_CCAEN_bm;

    /* Clear status register. */
    pal_trx_reg_read(RG_IRQ_STATUS);

    /* Enable main Trx IRQ. */
    pal_trx_irq_en();

    /* Re-enable all interrupts. */
    pal_global_irq_enable();
}

/**
 * @brief Initializes the transceiver
 *
 * This function is called to initialize the transceiver.
 *
 * @return MAC_SUCCESS  if the transceiver state is changed to TRX_OFF and the
 *                 current device part number and version number are correct;
 *         FAILURE otherwise
 */
static retval_t trx_init(void)
{
    tal_trx_status_t trx_status;
    uint8_t poll_counter = 0;

    /* Ensure control lines have correct levels. */
    PAL_RST_HIGH();
    PAL_SLP_TR_LOW();

    pal_timer_delay(P_ON_TO_CLKM_AVAILABLE_TYP_US);

    /* Apply reset pulse */
    PAL_RST_LOW();
    pal_timer_delay(RST_PULSE_WIDTH_US);
    PAL_RST_HIGH();

    /* Verify that the trx has reached TRX_OFF. */
    poll_counter = 0;
    do
    {
        /* Wait a short time interval. */
        pal_timer_delay(TRX_POLL_WAIT_TIME_US);

        trx_status = (tal_trx_status_t)pal_trx_bit_read(SR_TRX_STATUS);

        /* Wait not more than max. value of TR2. */
        if (poll_counter == RESET_TO_TRX_OFF_ATTEMPTS)
        {
#if (DEBUG > 0)
            pal_alert();
#endif
            return FAILURE;
        }
        poll_counter++;
    }
    while (trx_status != TRX_OFF);

    tal_trx_status = TRX_OFF;

#if !defined(FPGA_EMULATION)
    /* Check if actually running on an ATmegaRFR2 device. */
    if (ATMEGARFR2_PART_NUM != pal_trx_reg_read(RG_PART_NUM))
    {
        return FAILURE;
    }
#endif
    return MAC_SUCCESS;
}

void trx_irq_handler_cb(void)
{
	trx_irq_reason_t trx_irq_cause;

	trx_irq_cause = (trx_irq_reason_t) pal_trx_reg_read(RG_IRQ_STATUS);

	if (trx_irq_cause & TRX_IRQ_TRX_END) {
		/*
		 * TRX_END reason depends on if the trx is currently used for
		 * transmission or reception.
		 */
		if (tal_state == TAL_TX_AUTO) {
			handle_tx_end_irq();
		} else {	/* Other tal_state than TAL_TX_... */
			/* Handle rx interrupt. */
			handle_received_frame_irq();
		}
	}
}

static void generate_rand_seed(void)
{
	uint16_t seed = 0;
	uint8_t cur_random_val = 0;

	set_trx_state(CMD_RX_ON);

	/*
	 * We need to disable TRX IRQs while generating random values in RX_ON,
	 * we do not want to receive frames at this point of time at all.
	 */
	ENTER_TRX_REGION();

	/*
	 * The 16-bit random value is generated from various 2-bit random values.
	 */
	for (uint8_t i = 0; i < 8; i++) {
		/* Now we can safely read the 2-bit random number. */
		cur_random_val = pal_trx_bit_read(SR_RND_VALUE);
		seed = seed << 2;
		seed |= cur_random_val;
	}

	set_trx_state(CMD_FORCE_TRX_OFF);

	/*
	 * Now we need to clear potential pending TRX IRQs and
	 * enable the TRX IRQs again.
	 */
	pal_trx_reg_read(RG_IRQ_STATUS);
	CLEAR_TRX_IRQ();
	LEAVE_TRX_REGION();

	/* Set the seed for the random number generator. */
	srand(seed);
}