esp32 rs485一对多通信 idf代码

以下是使用 ESP-IDF 实现 ESP32 RS485 一对多通信的示例代码：

#include <stdio.h>
#include "driver/uart.h"
#include "driver/gpio.h"

#define UART_NUM UART_NUM_1
#define TXD_PIN (GPIO_NUM_4)
#define RXD_PIN (GPIO_NUM_5)
#define RS485_EN_PIN (GPIO_NUM_21)

#define RS485_BAUD_RATE 9600
#define RS485_DATA_BITS UART_DATA_8_BITS
#define RS485_PARITY UART_PARITY_DISABLE
#define RS485_STOP_BITS UART_STOP_BITS_1
#define RS485_FLOW_CTRL UART_HW_FLOWCTRL_DISABLE

#define RS485_FRAME_SIZE 8
#define RS485_DEVICE_COUNT 4

static void rs485_init() {
    uart_config_t uart_config = {
        .baud_rate = RS485_BAUD_RATE,
        .data_bits = RS485_DATA_BITS,
        .parity = RS485_PARITY,
        .stop_bits = RS485_STOP_BITS,
        .flow_ctrl = RS485_FLOW_CTRL,
    };
    uart_param_config(UART_NUM, &uart_config);
    uart_set_pin(UART_NUM, TXD_PIN, RXD_PIN, UART_PIN_NO_CHANGE, UART_PIN_NO_CHANGE);
    uart_driver_install(UART_NUM, RS485_FRAME_SIZE * RS485_DEVICE_COUNT, 0, 0, NULL, 0);
    gpio_set_direction(RS485_EN_PIN, GPIO_MODE_OUTPUT);
}

static void rs485_enable_tx() {
    gpio_set_level(RS485_EN_PIN, 1);
}

static void rs485_disable_tx() {
    gpio_set_level(RS485_EN_PIN, 0);
}

static void rs485_send_frame(uint8_t device_id, uint8_t *data) {
    rs485_enable_tx();
    uart_write_bytes(UART_NUM, (const char *)&device_id, 1);
    uart_write_bytes(UART_NUM, (const char *)data, RS485_FRAME_SIZE - 1);
    rs485_disable_tx();
}

void app_main() {
    rs485_init();

    uint8_t data[RS485_FRAME_SIZE - 1] = { 0x01, 0x02, 0x03, 0x04, 0x05, 0x06, 0x07 };
    for (int i = 1; i <= RS485_DEVICE_COUNT; i++) {
        rs485_send_frame(i, data);
    }
}

在这个示例中，我们使用 `uart_driver_install()` 函数配置 UART 驱动程序，以便能够发送 RS485 帧。我们使用 GPIO 配置 RS485 发送使能引脚，并使用 `rs485_enable_tx()` 和 `rs485_disable_tx()` 函数控制该引脚的状态。`rs485_send_frame()` 函数用于发送带有设备 ID 的 RS485 帧。

在 `app_main()` 函数中，我们发送相同的数据帧到四个不同的设备。你可以根据需要修改此代码以适应你的特定应用程序。