Errors with SB ADMIN and CG

I'am going to develop an app that performs a set of CRUD operations on a set of mysql tables for an office application. I decided to integrate coddeigniter+grocerycrud into sb admin 2. I followed the tutorial available on this web site: http://www.tutorials.kode-blog.com/codeigniter-admin-panel, dowloading from the discussion a file with the whole sample (it is a package that merges codeigniter, sb admin 2, hmvc codeigniter and templates.

my controller is disigned in this way:

<?php
class Tests extends Admin_Controller {


    function __construct() {
        parent::__construct();
$this->load->database();
        $this->load->helper('url');
        $this->load->library('grocery_CRUD');
    }


    public function index() {
$crud = new grocery_CRUD();
        $crud->set_table('test'); 
$output = $crud->render();
        
$data['output'] = $output;
        $data['page'] = $this->config->item('ci_my_admin_template_dir_admin') . "tests_view";
        $this->load->view($this->_container, $data);
}
}

My view is designed as:

<div id="page-wrapper">
    <div class="row">
        <div class="col-lg-12">
            <div class="page-header users-header">
                <h2>Test</h2>
            </div>
        </div>
        <!-- /.col-lg-12 -->
    </div>
    <!-- /.row -->
    <div class="row">
        <div class="col-lg-12">
            <div class="panel panel-default">
                <div class="panel-heading">
                    Test
                </div>
                <!-- /.panel-heading -->
                <div class="panel-body">
                    <div class="dataTable_wrapper">


                                <?php echo $output; ?>


                    </div>
                </div>
                <!-- /.panel-body -->
            </div>
            <!-- /.panel -->
        </div>
        <!-- /.col-lg-12 -->
    </div>
</div>
</div>




<!-- /#page-wrapper -->

but I got this error

A PHP Error was encountered

Severity: 4096

Message: Object of class stdClass could not be converted to string

I realized that the usual call

:
$output = $crud->render();
$this->_example_output($output);:

public function _example_output($output = null) {
$this->load->view('example.php',$output);
}

is different from the new code.

Please could you help me?

Is there some developer that has tested the integration of Codeigniter+GroceryCrud with sb admin 2 (Bootstrap, jquery, etc)?

thanks in advance

Alex

acor