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#include <stdio.h>
#include <stdbool.h>
#include <stdlib.h>
#include <inttypes.h>
#include <math.h>
#include "freertos/FreeRTOS.h"
#include "freertos/task.h"
#include "driver/gpio.h"
#include "esp_attr.h"
#include "FreeRTOSConfig.h"
#include "esp_pm.h"
#include "soc/gpio_struct.h"
#include "esp_timer.h"

// GPIO output pins for SPI
#define SCLK_PIN 18
#define MOSI_PIN 23
#define CS_PIN 5
#define OUTPUT_PINS  (1ULL << SCLK_PIN) | (1ULL << MOSI_PIN) | (1ULL << CS_PIN)

#define SPI_DATA_SIZE 256

DRAM_ATTR uint16_t _spi_tx_data[SPI_DATA_SIZE];

static uint32_t SCLK_VALUE = 1 << SCLK_PIN;
static uint32_t MOSI_VALUE = 1 << MOSI_PIN;
static uint32_t CS_VALUE = 1 << CS_PIN;

static void init_gpio() {
    gpio_config_t io_conf = {};
    io_conf.intr_type = GPIO_INTR_DISABLE;
    io_conf.mode = GPIO_MODE_OUTPUT;
    io_conf.pin_bit_mask = OUTPUT_PINS;	// bit mask of the pins that you want to set,e.g.GPIO18/19
    io_conf.pull_down_en = GPIO_PULLDOWN_DISABLE;	// == 0
    io_conf.pull_up_en = GPIO_PULLUP_DISABLE;	// == 0
    ESP_ERROR_CHECK(gpio_config(&io_conf));

    ESP_ERROR_CHECK(gpio_set_level(CS_PIN, 1));
}

static void init_sine_data() {
	float PI = 3.14159265;
	uint32_t max_value = 4095;	// 12 bit
	uint32_t step_size = max_value / SPI_DATA_SIZE;

	for (int i = 0; i < SPI_DATA_SIZE; i++) {
		uint16_t value = 2047 + round(2047 * sin(i * step_size * PI / 180));
		_spi_tx_data[i] = (value & 0x0FFF) | 0x3000;	// value is 12 bit OR 0x3000 for Gain = 1
	}
}

static void IRAM_ATTR tx_16bit_to_DAC(uint16_t value) {
	gpio_set_level(CS_PIN, 0);	// activate CS DAC

	for (uint16_t mask = 0x8000; mask > 0; mask >>= 1) {
		gpio_set_level(SCLK_PIN, 0);
		gpio_set_level(MOSI_PIN, (value & mask) != 0);
		gpio_set_level(SCLK_PIN, 1);
	}

	gpio_set_level(SCLK_PIN, 0);
	gpio_set_level(CS_PIN, 1);	// deactivate CS DAC
}

static void IRAM_ATTR tx_16bit_to_DAC_low_level(uint16_t value) {
	// Setting and clearing GPIO pins using out_w1ts & out_w1tc only for GPIO pin numbers < 32 !!
	// See gpio_ll.h line 430: 'gpio_ll_set_level(..)'

	GPIO.out_w1tc = CS_VALUE;		// gpio_set_level(CS_PIN, 0);	// activate CS DAC

	for (uint16_t mask = 0x8000; mask > 0; mask >>= 1) {
		GPIO.out_w1tc = SCLK_VALUE;	// gpio_set_level(SCLK_PIN, 0);
		if ((value & mask) != 0) {	// gpio_set_level(MOSI_PIN, (value & mask) != 0);
			GPIO.out_w1ts = MOSI_VALUE;
		}
		else {
			GPIO.out_w1tc = MOSI_VALUE;
		}
		GPIO.out_w1ts = SCLK_VALUE;	// gpio_set_level(SCLK_PIN, 1);
	}

	GPIO.out_w1tc = SCLK_VALUE;		// gpio_set_level(SCLK_PIN, 0);
	GPIO.out_w1ts = CS_VALUE;		// gpio_set_level(CS_PIN, 1);	// deactivate CS DAC
}

static void IRAM_ATTR tx_signal_to_DAC() {
	for (int i = 0; i < SPI_DATA_SIZE; i++) {
		// tx_16bit_to_DAC(_spi_tx_data[i]);	// 1 update takes 12 us, 9.6 times too slow
		tx_16bit_to_DAC_low_level(_spi_tx_data[i]);	// 1 update takes 2.6 us, 2.1 times too slow
	}
}

void spi_test(void * param) {
	init_gpio();
	init_sine_data();	// init table with sine values

	while (true) {
		tx_signal_to_DAC();
		vTaskDelay(200 / portTICK_PERIOD_MS);
	}
}

void app_main(void) {
	static uint8_t ucParams = 23;
	TaskHandle_t pCreatedTask = NULL;

	// Run on APP CORE
	xTaskCreatePinnedToCore(spi_test, "SPI_test", 2048, &ucParams, 19 | portPRIVILEGE_BIT, &pCreatedTask, 1);
	configASSERT(pCreatedTask);
}