Log Mysql errors

[eluser]Unknown[/eluser]
there is a way to log all the mysql log? or increse the show error level?

im recibin
A Database Error Occurred
Unable to connect to your database server using the provided settings.

i check the databse.php and all the atributes are ok

$db['default']['hostname'] = "localhost";
$db['default']['username'] = "maternet_db";
$db['default']['password'] = "cagaste";
$db['default']['database'] = "maternet_db";
$db['default']['dbdriver'] = "mysql";
$db['default']['dbprefix'] = "";
$db['default']['pconnect'] = TRUE;
$db['default']['db_debug'] = TRUE;
$db['default']['cache_on'] = FALSE;
$db['default']['cachedir'] = "";
$db['default']['char_set'] = "utf8";
$db['default']['dbcollat'] = "utf8_general_ci";