#include <Arduino.h>
#include <stdlib.h>
#include <stdint.h>
#include <stddef.h>
#include <driver/uart.h>

#define ECHO_UART_PORT UART_NUM_2
#define ECHO_TEST_TXD   (23)
#define ECHO_TEST_RXD   (22)
#define ECHO_TEST_RTS   (18)
#define ECHO_TEST_CTS  UART_PIN_NO_CHANGE
#define BUF_SIZE        (127)
#define BAUD_RATE       (115200)
#define PACKET_READ_TICS        (100 / portTICK_RATE_MS)
static const char *TAG = "RS485_ECHO_APP";

void setup() {
    Serial.begin(115200); //uses UART_NUM_0
    //configure UART_NUM_2 for RS485
    const uart_port_t uart_num = ECHO_UART_PORT;
    uart_config_t uart_config = {
        .baud_rate = BAUD_RATE,
        .data_bits = UART_DATA_8_BITS,
        .parity = UART_PARITY_DISABLE,
        .stop_bits = UART_STOP_BITS_1,
        .flow_ctrl = UART_HW_FLOWCTRL_DISABLE,
        .rx_flow_ctrl_thresh = 122,
    };

    Serial.println("Start RS485 application test and configure UART.");

    // Configure UART parameters
    uart_param_config(uart_num, &uart_config);

    Serial.println("UART set pins, mode and install driver.");
    // Set UART1 pins(TX: IO23, RX: I022, RTS: IO18, CTS: IO19)
    uart_set_pin(uart_num, ECHO_TEST_TXD, ECHO_TEST_RXD, ECHO_TEST_RTS, ECHO_TEST_CTS);

    // Install UART driver (we don't need an event queue here)
    // In this example we don't even use a buffer for sending data.
    uart_driver_install(uart_num, BUF_SIZE * 2, 0, 0, NULL, 0);

    // Set RS485 half duplex mode
    uart_set_mode(uart_num, UART_MODE_RS485_HALF_DUPLEX);

    ESP_LOGI(TAG, "UART start recieve loop.\r\n");
    uart_write_bytes(uart_num, "Start RS485 UART test.\r\n", 24);
}

void loop() {
    const uart_port_t uart_num = ECHO_UART_PORT;
    // Allocate buffers for UART
    uint8_t* data = (uint8_t*) malloc(BUF_SIZE);

    //Read data from UART
    int len = uart_read_bytes(uart_num, data, BUF_SIZE, PACKET_READ_TICS);

    //Write data back to UART
    if (len > 0) {
        uart_write_bytes(uart_num, "\r\n", 2);
        char prefix[] = "RS485 Received: [";
        uart_write_bytes(uart_num, prefix, (sizeof(prefix) - 1));

        Serial.println("Received "+  String(len) + "  bytes:");
        printf("[ ");
        for (int i = 0; i < len; i++) {
            printf("0x%.2X ", (uint8_t)data[i]);
            uart_write_bytes(uart_num, (const char*)&data[i], 1);
            // Add a Newline character if you get a return charater from paste (Paste tests multibyte receipt/buffer)
            if (data[i] == '\r') {
                uart_write_bytes(uart_num, "\n", 1);
            }
        }
        printf("] \n");
        uart_write_bytes(uart_num, "]\r\n", 3);
    } else {
        // Echo a "." to show we are alive while we wait for input
        uart_write_bytes(uart_num, ".", 1);
    }
}