Yesterday I spended some time with this but with no luck. The input from serial is not working properly and I can not do login. Perhaps my usb ttl is broken, I'll try again with other just in case.
Finally I acomplished to get the login prompt.
I will put a photo later, from right to left - being left the pinhole nearest to the heatsink - the pins are Gnd, Rx and Tx, both Rx and Tx have a square painted under the pinhole.
Default user and password are "admin" "admin" but instead of login the shell gets disabled and the "press enter to enable the shell" (or something) appears on screen. I've attempted to login with different combinations but as expected without any luck.
uBoot seems locked, or at least the "press any key to interrupt" doesn't show so ATM i'm unable to go further with this.