After some testing because it was impossible upload anything, I've found an error on printed circuit board (see photo) of mini-arduino marked as "Dswy-Robot".
RXD signal (on longer side) is not connected to any pin of Atmega328, so is not possible upload any program via serial port. Only the RXD on the shorter side is connected to the right pin of the Atmega328.
To solve this problem you must connect together both RXD (or use only RXD on shorter side).
During some tests I've used an AVR USB ASP programmer without any problem. Anyway... after connecting both RXD it works as expected. And yes, this model has a nice PCB layout (RXD issue excluded...).
