/* Megumin LED display firmware
 * Copyright (C) 2018 Sebastian Götte <code@jaseg.net>
 * 
 * This program is free software: you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 * 
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 * 
 * You should have received a copy of the GNU General Public License
 * along with this program.  If not, see <http://www.gnu.org/licenses/>.
 */

#include "adc.h"

#include <stdbool.h>
#include <stdlib.h>

#define DETECTOR_CHANNEL a

volatile uint16_t adc_buf[ADC_BUFSIZE];
volatile struct adc_state adc_state = {0};
#define st adc_state
volatile struct adc_measurements adc_data;

static void adc_dma_init(int burstlen, bool enable_interrupt);
static void adc_timer_init(int psc, int ivl);


/* Mode that can be used for debugging */
void adc_configure_scope_mode(uint8_t channel_mask, int sampling_interval_ns) {
	/* The constant SAMPLE_FAST (0) when passed in as sampling_interval_ns is handled specially in that we turn the ADC
	to continuous mode to get the highest possible sampling rate. */

	/* First, disable trigger timer, DMA and ADC in case we're reconfiguring on the fly. */
    TIM1->CR1 &= ~TIM_CR1_CEN;
    ADC1->CR &= ~ADC_CR_ADSTART;
    DMA1_Channel1->CCR &= ~DMA_CCR_EN;

	/* keep track of current mode in global variable */
	st.adc_mode = ADC_SCOPE;

	adc_dma_init(sizeof(adc_buf)/sizeof(adc_buf[0]), true);

    /* Clock from PCLK/4 instead of the internal exclusive high-speed RC oscillator. */
    ADC1->CFGR2 = (2<<ADC_CFGR2_CKMODE_Pos); /* Use PCLK/4=12MHz */
    /* Sampling time 13.5 ADC clock cycles -> total conversion time 2.17us*/
    ADC1->SMPR  = (2<<ADC_SMPR_SMP_Pos);

	/* Setup DMA and triggering */
	if (sampling_interval_ns == SAMPLE_FAST) /* Continuous trigger */
		ADC1->CFGR1 = ADC_CFGR1_DMAEN | ADC_CFGR1_DMACFG | ADC_CFGR1_CONT;
	else /* Trigger from timer 1 Channel 4 */
		ADC1->CFGR1 = ADC_CFGR1_DMAEN | ADC_CFGR1_DMACFG | (2<<ADC_CFGR1_EXTEN_Pos) | (1<<ADC_CFGR1_EXTSEL_Pos);
    ADC1->CHSELR = channel_mask;
	/* Perform self-calibration */
    ADC1->CR |= ADC_CR_ADCAL;
    while (ADC1->CR & ADC_CR_ADCAL)
        ;
	/* Enable conversion */
    ADC1->CR |= ADC_CR_ADEN;
    ADC1->CR |= ADC_CR_ADSTART;

	if (sampling_interval_ns == SAMPLE_FAST)
		return; /* We don't need the timer to trigger in continuous mode. */

	/* An ADC conversion takes 1.1667us, so to be sure we don't get data overruns we limit sampling to every 1.5us.
	Since we don't have a spare PLL to generate the ADC sample clock and re-configuring the system clock just for this
	would be overkill we round to 250ns increments. The minimum sampling rate is about 60Hz due to timer resolution. */
	int cycles = sampling_interval_ns > 1500 ? sampling_interval_ns/250 : 6;
	if (cycles > 0xffff)
		cycles = 0xffff;
	adc_timer_init(12/*250ns/tick*/, cycles);
}

/* FIXME figure out the proper place to configure this. */
#define ADC_TIMER_INTERVAL_US 20

/* Regular operation receiver mode. */
void adc_configure_monitor_mode(const struct command_if_def *cmd_if) {
	/* First, disable trigger timer, DMA and ADC in case we're reconfiguring on the fly. */
    TIM1->CR1 &= ~TIM_CR1_CEN;
    ADC1->CR &= ~ADC_CR_ADSTART;
    DMA1_Channel1->CCR &= ~DMA_CCR_EN;

	/* keep track of current mode in global variable */
	st.adc_mode = ADC_MONITOR;

	for (int i=0; i<NCH; i++)
		st.adc_aggregate[i] = 0;
	st.mean_aggregator[0] = st.mean_aggregator[1] = st.mean_aggregator[2] = 0; 
	st.mean_aggregate_ctr = 0;

    st.det_st.hysteresis_mv = 6000;
    /* base_cycles * the ADC timer interval (20us) must match the driver's AC period. */ 
    st.det_st.base_interval_cycles = 40; /* 40 * 20us = 800us/1.25kHz */

	st.det_st.sync = 0;
	st.det_st.last_bit = 0;
	st.det_st.committed_len_ctr = st.det_st.len_ctr = 0;
	xfr_8b10b_reset((struct state_8b10b_dec *)&st.det_st.rx8b10b);
    reset_receiver((struct proto_rx_st *)&st.det_st.rx_st, cmd_if);

	adc_dma_init(NCH, true);

	/* Setup DMA and triggering: Trigger from Timer 1 Channel 4 */
    ADC1->CFGR1 = ADC_CFGR1_DMAEN | ADC_CFGR1_DMACFG | (2<<ADC_CFGR1_EXTEN_Pos) | (1<<ADC_CFGR1_EXTSEL_Pos);
    /* Clock from PCLK/4 instead of the internal exclusive high-speed RC oscillator. */
    ADC1->CFGR2 = (2<<ADC_CFGR2_CKMODE_Pos); /* Use PCLK/4=12MHz */
    /* Sampling time 13.5 ADC clock cycles -> total conversion time 2.17us*/
    ADC1->SMPR  = (2<<ADC_SMPR_SMP_Pos);
    /* Internal VCC and temperature sensor channels */
    ADC1->CHSELR = ADC_CHSELR_CHSEL0 | ADC_CHSELR_CHSEL1 | ADC_CHSELR_CHSEL16 | ADC_CHSELR_CHSEL17;
    /* Enable internal voltage reference and temperature sensor */
    ADC->CCR = ADC_CCR_TSEN | ADC_CCR_VREFEN;
    /* Perform ADC calibration */
    ADC1->CR |= ADC_CR_ADCAL;
    while (ADC1->CR & ADC_CR_ADCAL)
        ;
    /* Enable ADC */
    ADC1->CR |= ADC_CR_ADEN;
    ADC1->CR |= ADC_CR_ADSTART;

    /* Initialize the timer. Set the divider to get a nice round microsecond tick. The interval must be long enough to
     * comfortably fit all conversions inside. There should be some margin since the ADC runs off its own internal RC
     * oscillator and will drift w.r.t. the system clock. 20us is a nice value when four channels are selected (A, B,
     * T and V).
     */
    adc_timer_init(SystemCoreClock/1000000/*1.0us/tick*/, 20/* us */);
}

static void adc_dma_init(int burstlen, bool enable_interrupt) {
    /* Configure DMA 1 Channel 1 to get rid of all the data */
    DMA1_Channel1->CPAR = (unsigned int)&ADC1->DR;
    DMA1_Channel1->CMAR = (unsigned int)&adc_buf;
    DMA1_Channel1->CNDTR = burstlen;
    DMA1_Channel1->CCR = (0<<DMA_CCR_PL_Pos);
    DMA1_Channel1->CCR |=
          DMA_CCR_CIRC /* circular mode so we can leave it running indefinitely */
        | (1<<DMA_CCR_MSIZE_Pos) /* 16 bit */
        | (1<<DMA_CCR_PSIZE_Pos) /* 16 bit */
        | DMA_CCR_MINC
        | (enable_interrupt ? DMA_CCR_TCIE : 0); /* Enable transfer complete interrupt. */

	if (enable_interrupt) {
		/* triggered on transfer completion. We use this to process the ADC data */
		NVIC_EnableIRQ(DMA1_Channel1_IRQn);
		NVIC_SetPriority(DMA1_Channel1_IRQn, 2<<5);
	} else {
		NVIC_DisableIRQ(DMA1_Channel1_IRQn);
		DMA1->IFCR |= DMA_IFCR_CGIF1;
	}

    DMA1_Channel1->CCR |= DMA_CCR_EN; /* Enable channel */
}

static void adc_timer_init(int psc, int ivl) {
    TIM1->BDTR  = TIM_BDTR_MOE; /* MOE is needed even though we only "output" a chip-internal signal TODO: Verify this. */
    TIM1->CCMR2 = (6<<TIM_CCMR2_OC4M_Pos); /* PWM Mode 1 to get a clean trigger signal */
    TIM1->CCER  = TIM_CCER_CC4E; /* Enable capture/compare unit 4 connected to ADC */
    TIM1->CCR4  = 1; /* Trigger at start of timer cycle */
	/* Set prescaler and interval */
    TIM1->PSC   = psc-1;
    TIM1->ARR   = ivl-1;
    /* Preload all values */
    TIM1->EGR  |= TIM_EGR_UG;
    TIM1->CR1   = TIM_CR1_ARPE;
    /* And... go! */
    TIM1->CR1  |= TIM_CR1_CEN;
}

/* This acts as a no-op that provides a convenient point to set a breakpoint for the debug scope logic */
static void gdb_dump(void) {
}

/* Called on reception of a bit. This feeds the bit to the 8b10b state machine. When the 8b10b state machine recognizes
 * a received symbol, this in turn calls receive_symbol. Since this is called at sampling time roughly halfway into a
 * bit being received, receive_symbol is called roughly half-way through the last bit of the symbol, just before the
 * symbol's end.
 */
void receive_bit(struct bit_detector_st *st, int bit) {
    int symbol = xfr_8b10b_feed_bit((struct state_8b10b_dec *)&st->rx8b10b, bit);
    if (symbol == -K28_1)
        st->sync = 1;

    if (symbol == -DECODING_IN_PROGRESS)
        return;

    if (symbol == -DECODING_ERROR)
        st->sync = 0;
        /* Fall through so we also pass the error to receive_symbol */

    receive_symbol(&st->rx_st, symbol);

    /* Exceedingly handy piece of debug code: The Debug Scope 2000 (TM) */
    /*
    static int debug_buf_pos = 0;
    if (st->sync) {
        if (debug_buf_pos < NCH) {
                debug_buf_pos = NCH;
        } else {
            adc_buf[debug_buf_pos++] = symbol;

            if (debug_buf_pos >= sizeof(adc_buf)/sizeof(adc_buf[0])) {
                debug_buf_pos = 0;
                st->sync = 0;
                gdb_dump();
                for (int i=0; i<sizeof(adc_buf)/sizeof(adc_buf[0]); i++)
                    adc_buf[i] = -255;
            }
        }
    }
    */
}

/* From a series of detected line levels, extract discrete bits. This self-synchronizes to signal transitions. This
 * expects base_interval_cycles to be set correctly. When a bit is detected, this calls receive_bit(st, bit). The call
 * to receive_bit happens at the sampling point about half-way through the bit being received.
 */
void bit_detector(struct bit_detector_st *st, int a) {
    int new_bit = st->last_bit;
    int diff = a-5500; /* FIXME extract constants */
    if (diff < - st->hysteresis_mv/2)
        new_bit = 0;
    else if (diff > st->hysteresis_mv/2)
        new_bit = 1;
    else
        blank(); /* Safety, in case we get an unexpected transition */

    st->len_ctr++;
    if (new_bit != st->last_bit) { /* On transition */
        st->last_bit = new_bit;
        st->len_ctr = 0;
        st->committed_len_ctr = st->base_interval_cycles>>1; /* Commit first half of bit */

    } else if (st->len_ctr >= st->committed_len_ctr) {
        /* The line stayed constant for a longer interval than the commited length. Interpret this as a transmitted bit.
         *
         *     +-- Master clock edges     -->| - - - - |<-- One bit period
         *     |                             |         |
         * 1   X         X         X         X         X         X         X         X
         * ____/^^^^*^^^^\_______________________________________/^^^^*^^^^^^^^^*^^^^\__________________________________
         * 0   v    ^                                                 v         ^
         *     |    |                                                 |         |
         *     |    +-------------------------------+                 +---------+
         *     |                                    |                 |        
         *     At this point, commit 1/2 bit (until here). This       When we arrive at the committed value, commit next
         *     happens in the block above.                            full bit as we're now right in the middle of the
         *                                                            first bit. This happens in the line below.
         */

        /* Commit second half of this and first half of possible next bit */
        st->committed_len_ctr += st->base_interval_cycles;
        receive_bit(st, st->last_bit);
    }
}

void DMA1_Channel1_IRQHandler(void) {
    /* ISR timing measurement for debugging */
    //int start = SysTick->VAL;

    /* Clear the interrupt flag */
    DMA1->IFCR |= DMA_IFCR_CGIF1;
    
    if (st.adc_mode == ADC_SCOPE)
        return;

    /* FIXME This code section currently is a mess since I left it as soon as it worked. Re-work this and try to get
     * back all the useful monitoring stuff, in particular temperature. */

    /* This has been copied from the code examples to section 12.9 ADC>"Temperature sensor and internal reference
     * voltage" in the reference manual with the extension that we actually measure the supply voltage instead of
     * hardcoding it. This is not strictly necessary since we're running off a bored little LDO but it's free and
     * the current supply voltage is a nice health value.
     */
    // FIXME DEBUG adc_data.vcc_mv = (3300 * VREFINT_CAL)/(st.adc_aggregate[VREF_CH]);

    int64_t vcc = 3300;
    /* FIXME debug
    int64_t vcc = adc_data.vcc_mv;
    int64_t read = st.adc_aggregate[TEMP_CH] * 10 * 10000;
    int64_t cal = TS_CAL1 * 10 * 10000;
    adc_data.temp_celsius_tenths = 300 + ((read/4096 * vcc) - (cal/4096 * 3300))/43000;
    */

    /* Calculate the line voltage from the measured ADC voltage and the used resistive divider ratio */
    const long vmeas_r_total = VMEAS_R_HIGH + VMEAS_R_LOW;
    //int a = adc_data.vmeas_a_mv = (st.adc_aggregate[VMEAS_A]*(vmeas_r_total * vcc / VMEAS_R_LOW)) >> 12;
    int a = adc_data.vmeas_a_mv = (adc_buf[VMEAS_A]*13300) >> 12;
    bit_detector((struct bit_detector_st *)&st.det_st, a);

    /* ISR timing measurement for debugging */
    /*
    int end = SysTick->VAL;
    int tdiff = start - end;
    if (tdiff < 0)
        tdiff += SysTick->LOAD;
    st.dma_isr_duration = tdiff;
    */
}