Das habe ich auch gelesen:
Note: the TFTP flashing process requires that the product hardware id and version in the new image header match those in the existing image in flash, otherwise the new image is rejected, flashing is cancelled and the bootloader proceeds to boot the old image. When this happens, the following output is seen on the serial console:
original_product_id = ffffffff
original_product_ver = ffffffff
recovery_product_id = c7000002
recovery_product_ver = 01
auto update firmware: product id verify fail!
Autobooting in 1 seconds
Also komme ich nicht um Seriell herum? 