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#include "freertos/FreeRTOS.h"
#include "freertos/task.h"
#include "driver/rmt.h"
#include "esp_log.h"

static const char* TAG = "RMT";


//define the pins to use

#if ARDUINO_M5Stack_ATOM
  #define channel_0_input_pin 21  //unused pin on M5Atom-GPS module  
  #define channel_1_input_pin 25  //unused pin on M5Atom-GPS module   
  #define spareInputPin 2         //this pin is not actually correct.  just a placeholder
#elif ARDUINO_M5Stack_ATOMS3   //THIS IS AN ESP32-S3 BASED BOARD
  #define channel_0_input_pin 39   //unused pin on M5Atom-GPS module (with AtomS3-lite installed)
  #define channel_1_input_pin 38   //unused pin on M5Atom-GPS module (with AtomS3-lite installed)
  #define spareInputPin 14          //this pin is NOT actually correct.  Just a placeholder 
#endif


#define RECEIVER_CHANNELS_NUM 3
volatile uint16_t ReceiverChannels[RECEIVER_CHANNELS_NUM] = {0};
const uint8_t RECEIVER_CHANNELS[RECEIVER_CHANNELS_NUM] = { 1, 2, 3 };
const uint8_t RECEIVER_GPIOS[RECEIVER_CHANNELS_NUM] = { channel_0_input_pin, channel_1_input_pin, spareInputPin }; 


void setup() {
  Serial.begin(115200);
  ESP_LOGI(TAG, "Started");
  rmt_init(); //initialize the PWM monitor

}

void loop() {
  Serial.print("CH0=");
  Serial.print(ReceiverChannels[0]/8);
  Serial.print("us \t CH1=");
  Serial.print(ReceiverChannels[1]/8);
  Serial.print("us \t CH2=");
  Serial.print(ReceiverChannels[2]/8);
  Serial.println("us");
}



// receiver pulse length ranges from 8000 to 16000 centered around 12000 (units: ticks)
#define RECEIVER_CH_MIN 8000
#define RECEIVER_CH_CENTER 12000
#define RECEIVER_CH_MAX 16000

//note that the actual duty cycle is between 1000 and 2000 microseconds, so we're dividing by 8 to get the value we want
#define RMT_TICK_PER_US 8
// determines how many clock cycles one "tick" is
// [1..255], source is generally 80MHz APB clk

#define RMT_RX_CLK_DIV (80000000/RMT_TICK_PER_US/1000000)
// time before receiver goes idle
#define RMT_RX_MAX_US 3500





static void rmt_isr_handler(void* arg){
    // with reference to https://www.esp32.com/viewtopic.php?t=7116#p32383
    // but modified so that this ISR only checks chX_rx_end
    uint32_t intr_st = RMT.int_st.val;

    // see declaration of RMT.int_st:
    // takes the form of 
    // bit 0: ch0_tx_end
    // bit 1: ch0_rx_end
    // bit 2: ch0_err
    // bit 3: ch1_tx_end
    // bit 4: ch1_rx_end
    // ...
    // thus, check whether bit (channel*3 + 1) is set to identify
    // whether that channel has changed

    uint8_t i;
    for(i = 0; i < RECEIVER_CHANNELS_NUM; i++) {
        uint8_t channel = RECEIVER_CHANNELS[i];
        uint32_t channel_mask = BIT(channel*3+1);

        if (!(intr_st & channel_mask)) continue;

        #ifdef CONFIG_IDF_TARGET_ESP32S3   //NEW CODE FOR ESP32-S3 BOARD
          //if it's an S3 board, use different terminology
          RMT.chmconf[channel].conf1.rx_en_m = 0;  //NEW CODE FOR ESP32-S3 BOARD
          RMT.chmconf[channel].conf1.mem_owner_m = RMT_MEM_OWNER_TX;  //NEW CODE FOR ESP32-S3 BOARD
        #else
          RMT.conf_ch[channel].conf1.rx_en = 0;
          RMT.conf_ch[channel].conf1.mem_owner = RMT_MEM_OWNER_TX;
        #endif

        
        volatile rmt_item32_t* item = RMTMEM.chan[channel].data32;
        if (item) {
            ReceiverChannels[i] = item->duration0;
        }

        #ifdef CONFIG_IDF_TARGET_ESP32S3  //NEW CODE FOR ESP32-S3 BOARD
          //if it's an S3 board, use different terminology.  Updated code made using a mixture of guessing, and the following files/links:
          //  (ESP32 reference: https://github.com/espressif/esp-idf/blob/master/components/soc/esp32/include/soc/rmt_struct.h)
          //  (ESP32S3 compare: https://github.com/espressif/esp-idf/blob/master/components/soc/esp32s3/include/soc/rmt_struct.h)
          //  C:\Users\<USERNAME>\AppData\Local\Arduino15\packages\esp32\hardware\esp32\2.0.9\tools\sdk\esp32s3\include\soc\esp32s3\include\soc\rmt_struct.h
          //  C:\Users\<USERNAME>\AppData\Local\Arduino15\packages\esp32\hardware\esp32\2.0.9\tools\sdk\esp32s3\include\hal\esp32s3\include\hal\rmt_ll.h
          RMT.chmconf[channel].conf1.mem_wr_rst_m = 1;  //NEW CODE FOR ESP32-S3 BOARD
          RMT.chmconf[channel].conf1.mem_owner_m = RMT_MEM_OWNER_RX;  //NEW CODE FOR ESP32-S3 BOARD
          RMT.chmconf[channel].conf1.rx_en_m = 1;  //NEW CODE FOR ESP32-S3 BOARD
        #else
          RMT.conf_ch[channel].conf1.mem_wr_rst = 1;
          RMT.conf_ch[channel].conf1.mem_owner = RMT_MEM_OWNER_RX;
          RMT.conf_ch[channel].conf1.rx_en = 1;
        #endif

        //clear RMT interrupt status.
        RMT.int_clr.val = channel_mask;
    }
}

void rmt_init(void) {
    uint8_t i;

    rmt_config_t rmt_channels[RECEIVER_CHANNELS_NUM] = {};

    for (i = 0; i < RECEIVER_CHANNELS_NUM; i++) {
        ReceiverChannels[i] = RECEIVER_CH_CENTER;

        rmt_channels[i].channel = (rmt_channel_t) RECEIVER_CHANNELS[i];
        rmt_channels[i].gpio_num = (gpio_num_t) RECEIVER_GPIOS[i];
        rmt_channels[i].clk_div = RMT_RX_CLK_DIV;
        rmt_channels[i].mem_block_num = 1;
        rmt_channels[i].rmt_mode = RMT_MODE_RX;
        rmt_channels[i].rx_config.filter_en = true;
        rmt_channels[i].rx_config.filter_ticks_thresh = 100;
        rmt_channels[i].rx_config.idle_threshold = RMT_RX_MAX_US * RMT_TICK_PER_US;

        rmt_config(&rmt_channels[i]);
        rmt_set_rx_intr_en(rmt_channels[i].channel, true);
        rmt_rx_start(rmt_channels[i].channel, 1);
    }

    rmt_isr_register(rmt_isr_handler, NULL, 0, NULL);
    ESP_LOGI(TAG, "Init ISR on %d", xPortGetCoreID());
}