ESP32的串口使用队列接收256字节数据正常，但是将串口配置成485接收数据超过120字节后会自动分包，这是底层限制了485接收的数据长度还是配置上出现问题？
485配置如下：uart_config_t uart_config = {
        .baud_rate = baudrate,
        .data_bits = UART_DATA_8_BITS,
        .parity = uartparity,
        .stop_bits = UART_STOP_BITS_1,
        .flow_ctrl = UART_HW_FLOWCTRL_DISABLE,
        //.rx_flow_ctrl_thresh = 127
        .rx_flow_ctrl_thresh = 255
    };
    uart_param_config(EX_UART_NUM0, &uart_config);
    uart_set_pin(EX_UART_NUM0, HAL_RS485_TX_0, HAL_RS485_RX_0, HAL_RS485_DE_0, UART_PIN_NO_CHANGE);
    uart_driver_install(EX_UART_NUM0, BUF1_SIZE * 2, BUF1_SIZE * 2, 20, &uart_queue, 0);

    uart_set_mode(EX_UART_NUM0, UART_MODE_RS485_HALF_DUPLEX);
    //Set uart pattern detect function.
    uart_enable_pattern_det_intr(EX_UART_NUM0, '+', PATTERN_CHR_NUM1, 10000, 10, 10);
    //Reset the pattern queue length to record at most 20 pattern positions.
    uart_pattern_queue_reset(EX_UART_NUM0, 20);