/*
 * adc.c
 *
 * todo:
 * - use DMA
 */

#include "ch32x035_conf.h"


#define ADC_CHANNELS            8

#define CHAN_ENABLED            0x80

#define CHAN_MASK				0x7f
#define CHAN_IS_NORMAL          0
#define CHAN_IS_TOUCH           1
#define CHAN_IS_LIGHTSENSE      2

#define TOUCH_DEFAULT_CHARGE    0x4c
#define TOUCH_DEFAULT_THRESH    0x800
#define TOUCH_HYSTERESIS        66


typedef struct AdcChan {
    uint8_t chan;           // ADC channel number
    uint8_t type;           // ADC channel type (use above defines)
    uint8_t timing;         // sample rate for normal channels, charge values for touch-type channels
    uint8_t idx;            // rawval index
    uint16_t avg;           // averaged output
    uint16_t thresh;        // touch threshold
    uint16_t rawval[8];     // raw counts
} AdcChan;


static uint8_t adc_idx = 0;
static AdcChan adc_chan[ADC_CHANNELS] = {0};

static uint32_t touch_status = 0;



void adc_init()
{
    NVIC_InitTypeDef nvic;
	ADC_InitTypeDef adc = {0};
    
    // configure pin struct
    for (uint8_t i = 0; i < ADC_CHANNELS; i++) {
        adc_chan[i].type   = CHAN_ENABLED | CHAN_IS_TOUCH;
        adc_chan[i].timing = TOUCH_DEFAULT_CHARGE;
        adc_chan[i].thresh = TOUCH_DEFAULT_THRESH;
    }

    adc_chan[0].chan = ADC_Channel_0;
    adc_chan[0].timing = 0x4f;
    adc_chan[0].thresh = 3380;

    adc_chan[1].chan = ADC_Channel_1;
    adc_chan[1].thresh = 3580;

    adc_chan[2].chan = ADC_Channel_2;
    adc_chan[2].timing = 0x6f;
    adc_chan[2].thresh = 3380;

    adc_chan[3].chan = ADC_Channel_3;
    adc_chan[3].timing = 0x54;
    adc_chan[3].thresh = 3450;

    adc_chan[4].chan = ADC_Channel_4;
    adc_chan[4].timing = 0x44;
    adc_chan[4].thresh = 3000;

    adc_chan[5].chan = ADC_Channel_8;
    adc_chan[5].thresh = 3380;

    adc_chan[6].chan = ADC_Channel_13;
    adc_chan[6].timing = 0x4a;
    adc_chan[6].thresh = 3550;

    adc_chan[7].chan = ADC_Channel_9;
	adc_chan[7].type = CHAN_IS_LIGHTSENSE;
	adc_chan[7].timing = ADC_SampleTime_7Cycles;
    
    
    // configure actual peripheral
    ADC_DeInit(ADC1);

    ADC_CLKConfig(ADC1, ADC_CLK_Div6);

    adc.ADC_Mode                = ADC_Mode_Independent;
    adc.ADC_ScanConvMode        = DISABLE;
    adc.ADC_ContinuousConvMode  = DISABLE;
    adc.ADC_ExternalTrigConv    = ADC_ExternalTrigConv_None;
    adc.ADC_DataAlign           = ADC_DataAlign_Right;
    adc.ADC_NbrOfChannel        = 1;
    ADC_Init(ADC1, &adc);

    ADC_Cmd(ADC1, ENABLE);

	// configure ADC interrupt
	nvic.NVIC_IRQChannel = ADC1_IRQn;
    nvic.NVIC_IRQChannelPreemptionPriority = 0;
    nvic.NVIC_IRQChannelSubPriority = 4;
    nvic.NVIC_IRQChannelCmd = ENABLE;    

	// enable interrupt
    ADC_ITConfig(ADC1, ADC_IT_EOC, ENABLE);
    ADC1->STATR = 0;        // clear flags
    NVIC_Init(&nvic);
}

int8_t adc_get_tkey(uint8_t key_idx)
{
    return (touch_status & (1 << key_idx) ? 1 : 0);
}

__attribute((section(".ramfunc")))
void adc_next()
{
    AdcChan *chan;
    volatile uint8_t timeout = 0;

    // todo:
    // lightsense is timing-sensitive. will need to have this as an overridden channel?

    // get next index
    // so long as the channel is enabled
    do {
        adc_idx++;
		adc_idx %= (sizeof(adc_chan) / sizeof(adc_chan[0]));
        if (adc_chan[adc_idx].type & CHAN_ENABLED)
            break;
    } while (timeout++ < ADC_CHANNELS);

    // if nothing is enabled, break out
    if (timeout == ADC_CHANNELS)
        return;

    chan = &adc_chan[adc_idx];

    // configure sampling
    switch (chan->type & ~CHAN_ENABLED) {
        case CHAN_IS_NORMAL: {
			TKey1->CTLR1 &= ~ADC_TKENABLE;          // disable TouchKey

            // we don't have any
            break;
        }
        case CHAN_IS_TOUCH: {
            TKey1->CTLR1 |= ADC_TKENABLE;           // enable TouchKey
        
            ADC_RegularChannelConfig(ADC1, chan->chan, 1, ADC_SampleTime_11Cycles);
            TKey1->IDATAR1 = chan->timing & 0xf0;   // R32_TKEY1_CHGOFFSET Charging Time
            TKey1->RDATAR  = chan->timing & 0x0f;   // R32_TKEY1_ACT_DCG   Discharging Time
													// per the RM, setting RDATAR (ACT_DCG) starts the conversion
            
            break;
        }
        case CHAN_IS_LIGHTSENSE: {
            TKey1->CTLR1 &= ~ADC_TKENABLE;          // disable TouchKey

			// todo: use thresh as a "timeout" value maybe?
			// this way the other channels can be sampled, and each time we pass by
			// the lightsensor, if it isn't time to sample it, it is skipped.
			ADC_RegularChannelConfig(ADC1, chan->chan, 1, chan->timing & 0xf);
			ADC_SoftwareStartConvCmd(ADC1, ENABLE);
            break;
        }
    }
}

void adc_isr()
{
    AdcChan *chan;
    uint32_t v = 0;
	uint8_t amax, ashift;

    chan = &adc_chan[adc_idx];

    // conversion done
    if (ADC1->STATR & ADC_EOC) {
        chan->rawval[chan->idx] = ADC1->RDATAR;

		// how many averages should we do?
		switch (chan->type & CHAN_MASK) {
			case CHAN_IS_TOUCH: {
				amax = 4;
				ashift = 2;
				break;
			}
			default: {
				amax = 8;
				ashift = 3;
				break;
			}
		}

        chan->idx++;
        if (chan->idx >= amax) {
            chan->idx = 0;
            for (int i = 0; i < amax; i++) {
                v += chan->rawval[i];
            }
            chan->avg = v >> ashift;
            
            // calculate if touched if measuring a touch sensor
            if (amax == 4) {
                if (chan->avg <= chan->thresh) {
                    touch_status |=  (1 << adc_idx);
                }
                if (chan->avg > (chan->thresh + TOUCH_HYSTERESIS)) {
                    touch_status &= ~(1 << adc_idx);
                }
            }
        }
    }

    // flags cleared by software
    ADC1->STATR = 0;
}