hit CTRL+C in serial console connected to WRT

serial console (don't forget the trailing colon, but don't press enter yet!):
load -tftp -raw -addr=0xXXXXXXX -max=0x800000 :

workstation:
atftp --option "mode octet" --option "timeout  60" --verbose --trace -p -l openwrt-wrt610n_v1-squashfs.bin 192.168.1.1

serial console:
(press enter now!)
flash -ctheader -mem -size=0xYYYYYY 0xZZZZZZZ flash1.trx
reboot



0xXXXXXXX: location of current firmware, get it from the bootloader's output
0xYYYYYY:  size of new firmware, get it from the output of the load command
0xZZZZZZZ: location of new firmware, get it from the output of the load command