#include <ESP32SPISlave.h>

ESP32SPISlave slave;

static constexpr uint32_t BUFFER_SIZE {32};
uint8_t spi_slave_tx_buf[BUFFER_SIZE];
uint8_t spi_slave_rx_buf[BUFFER_SIZE];

void setup() {
    // Setup serial port
    Serial.begin(115200);

    // note: the default pins are different depending on the board
    // please refer to README Section "SPI Buses and SPI Pins" for more details
    slave.setDataMode(SPI_MODE0);

    // HSPI = CS: 15, CLK: 14, MOSI: 13, MISO: 12 -> default
    // VSPI = CS:  5, CLK: 18, MOSI: 23, MISO: 19
    slave.begin(VSPI); //VSPI mode
    //slave.begin();  //HSPI mode

    // clear buffers
    memset(spi_slave_tx_buf, 0, BUFFER_SIZE);
    memset(spi_slave_rx_buf, 0, BUFFER_SIZE);
}

void loop() {
    // if there is no transaction in queue, add transaction
    if (slave.remained() == 0)
        slave.queue(spi_slave_rx_buf, spi_slave_tx_buf, BUFFER_SIZE);

    // if transaction has completed from master,
    // available() returns the number of completed transactions,
    // and `spi_slave_rx_buf` is automatically updated
    while (slave.available()) {
        // do something with `spi_slave_rx_buf`
        // show received data
        for (size_t i = 0; i < slave.size(); ++i) {
            printf("%d ", spi_slave_rx_buf[i]);
        }
        printf("\n");
        slave.pop();
    }
}

/**
TASK MODE

#include <ESP32SPISlave.h>

ESP32SPISlave slave;

static constexpr uint32_t BUFFER_SIZE {32};
uint8_t spi_slave_tx_buf[BUFFER_SIZE];
uint8_t spi_slave_rx_buf[BUFFER_SIZE];

constexpr uint8_t CORE_TASK_SPI_SLAVE {0};
constexpr uint8_t CORE_TASK_PROCESS_BUFFER {0};

static TaskHandle_t task_handle_wait_spi = 0;
static TaskHandle_t task_handle_process_buffer = 0;

void task_wait_spi(void* pvParameters) {
    while (1) {
        ulTaskNotifyTake(pdTRUE, portMAX_DELAY);

        // block until the transaction comes from master
        slave.wait(spi_slave_rx_buf, spi_slave_tx_buf, BUFFER_SIZE);

        xTaskNotifyGive(task_handle_process_buffer);
    }
}

void task_process_buffer(void* pvParameters) {
    while (1) {
        ulTaskNotifyTake(pdTRUE, portMAX_DELAY);

        // do something with `spi_slave_rx_buf`

        slave.pop();

        xTaskNotifyGive(task_handle_wait_spi);
    }
}

void setup() {
    // note: the default pins are different depending on the board
    // please refer to README Section "SPI Buses and SPI Pins" for more details
    slave.setDataMode(SPI_MODE0);
    slave.begin(HSPI);

    xTaskCreatePinnedToCore(task_wait_spi, "task_wait_spi", 2048, NULL, 2, &task_handle_wait_spi, CORE_TASK_SPI_SLAVE);
    xTaskNotifyGive(task_handle_wait_spi);

    xTaskCreatePinnedToCore(task_process_buffer, "task_process_buffer", 2048, NULL, 2, &task_handle_process_buffer, CORE_TASK_PROCESS_BUFFER);
}

void loop() {
}
**/