This is the standard method for flashing via USB.
If the PC method fails, use PhoenixCard to create a "Burn" card: Insert a MicroSD card into your PC.
$ sunxi-fel write 0x2000 bootloader-sram.bin $ sunxi-fel exec 0x2000
Once a "Firmware Update Succeeds" message appears, the device will reboot automatically. ⚡ Troubleshooting