Power off the Atmel STK500
On the STK500, push the PROGRAM button while turning on the power.
Make sure there is a serial connection between the PC and the STK500 DSUB9 marked RS232 CTRL
Start AVR Studio 4, and from the Tools menu start the program 'Avr Prog'
Locate the firmware upgrade hex-file stk500.ebn by pushing the button in the Avr Prog Hex File window. The path for the stk500.ebn for a normal AVR Studio 4 installation is
C:\Program Files\Atmel\AVR Tools\STK500\STK500.ebn.
Push the Avr Prog Flash window. A progress bar will now appear while showing additional information messages. Wait until the verify operation is finished.button in the
Close the Avr Prog program
Power off and on the STK500 PCB. The STK500 is now ready to be used with the new firmware.