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#include <stdio.h>
#include <stdint.h>
#include "driver/uart.h"
#include "driver/gpio.h"
#include "freertos/FreeRTOS.h"
#include "freertos/task.h"
#include "esp_log.h"

#define ZONE_READ_REG_VAL 7000
#define MAX_ZONES 64
#define FRAME_SIZE 8
#define UART_NUM UART_NUM_2
#define TXD_PIN GPIO_NUM_41
#define RXD_PIN GPIO_NUM_42
#define RS485_ENABLE_PIN GPIO_NUM_2
#define SLAVE_ID 01
#define BAUD_RATE 9600
#define BUF_SIZE 1024

static void poll_all_zones(void) {
    uint8_t rx_data[135];
    uint8_t frame[FRAME_SIZE];

    uint16_t reg = ZONE_READ_REG_VAL;
    frame[0] = SLAVE_ID;
    frame[1] = 0x03;
    frame[2] = (reg >> 8) & 0xFF;
    frame[3] = reg & 0xFF;
    frame[4] = 0x00;
    frame[5] = MAX_ZONES & 0xFF;
    //uint16_t crc = modbus_crc16(frame, 6);
    frame[6] = 0xC3;//crc & 0xFF;
    frame[7] = 0x0D;//(crc >> 8) & 0xFF;

    gpio_set_level(RS485_ENABLE_PIN, 1);
    vTaskDelay(pdMS_TO_TICKS(10));
    uart_write_bytes(UART_NUM, (const char *)frame, FRAME_SIZE);
    uart_wait_tx_done(UART_NUM, pdMS_TO_TICKS(50));
    vTaskDelay(pdMS_TO_TICKS(10));
    gpio_set_level(RS485_ENABLE_PIN, 0);
    //vTaskDelay(pdMS_TO_TICKS(5));
    int len = uart_read_bytes(UART_NUM, rx_data, sizeof(rx_data), pdMS_TO_TICKS(100));
    printf("\n");
    if (len > 0) {
        
        for (int i = 0; i < sizeof(rx_data); i++) {
            printf("%02X ", rx_data[i]);
        }
        printf("\n");
    }
}

void rs485_task(void *arg) {
//    ESP_LOGI(TAG_RS485_DATA, "Zone polling task started");
    for (;;) {
        poll_all_zones();
        vTaskDelay(pdMS_TO_TICKS(200));
    }
}

void app_main(void) {
    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
    };

    // Init UART
    ESP_ERROR_CHECK(uart_driver_install(UART_NUM, 256, 0, 0, NULL, 0));
    ESP_ERROR_CHECK(uart_param_config(UART_NUM, &uart_config));
    ESP_ERROR_CHECK(uart_set_pin(UART_NUM, TXD_PIN, RXD_PIN, UART_PIN_NO_CHANGE, UART_PIN_NO_CHANGE));

    // Init RS485 direction control pins
    gpio_set_direction(RS485_ENABLE_PIN, GPIO_MODE_OUTPUT);

    gpio_set_level(RS485_ENABLE_PIN, 0);   // Default to RX mode
    vTaskDelay(50);
    xTaskCreate(rs485_task, "rs485_task", 8192, NULL, 5, NULL);
}

Code: Select all

static uint16_t modbus_crc16(uint8_t *buf, int len) {
    uint16_t crc = 0xFFFF;
    for (int pos = 0; pos < len; pos++) {
        crc ^= (uint16_t)buf[pos];
        for (int i = 0; i < 8; i++) {
            if (crc & 0x0001) {
                crc >>= 1;
                crc ^= 0xA001;
            } else {
                crc >>= 1;
            }
        }
    }
    return crc;
}

static void poll_all_zones(void) {
    uint8_t rx_data[256];
    uint8_t frame[FRAME_SIZE];

    uint16_t reg = ZONE_READ_REG_VAL;
    frame[0] = SLAVE_ID;
    frame[1] = 0x03;
    frame[2] = (reg >> 8) & 0xFF;
    frame[3] = reg & 0xFF;
    frame[4] = 0x00;
    frame[5] = MAX_ZONES & 0xFF;

    uint16_t crc = modbus_crc16(frame, 6);
    frame[6] = crc & 0xFF;          // CRC Low
    frame[7] = (crc >> 8) & 0xFF;   // CRC High

    uart_flush_input(UART_NUM); // clear old data

    gpio_set_level(RS485_ENABLE_PIN, 1);   // TX mode
    vTaskDelay(pdMS_TO_TICKS(2));          // guard time
    uart_write_bytes(UART_NUM, (const char *)frame, FRAME_SIZE);
    uart_wait_tx_done(UART_NUM, pdMS_TO_TICKS(50));
    vTaskDelay(pdMS_TO_TICKS(2));          // allow last byte to shift out
    gpio_set_level(RS485_ENABLE_PIN, 0);   // RX mode

    int len = uart_read_bytes(UART_NUM, rx_data, sizeof(rx_data), pdMS_TO_TICKS(200));

    if (len > 0) {
        printf("Received %d bytes: ", len);
        for (int i = 0; i < len; i++) {
            printf("%02X ", rx_data[i]);
        }
        printf("\n");
    } else {
        printf("No response\n");
    }
}