TP LINK W9980 Openwrt uboot problem

First of all, I apologize for bad English. The t key does not respond on the w9980 uboot display.
I press the tpl keys. I am copy and paste. but there is no reaction.
so i can't stop the auto boot. I can't enter code.
Trials were done with different usb serial port devices.
When I shorts with the r225 pin, the device switches to UART mode.