I tried different baud rate but it is not working.
I have found following on Serial Tutorial
Changing operating modes with USB Serial
Normally you press buttons to enter listening or DFU mode on the Photon or Electron. You can also trigger it by making a USB Serial connection at a specific baud rate.
For example, on the Mac you can use this command to enter DFU mode:
stty -f /dev/cu.usbmodemFD1141 14400
(The device name, cu.usbmodemFD1141 in this example, may be different on your computer.)
The special baud rates are:
14400 DFU mode (blinking yellow)
28800 Listening mode (blinking dark blue)
But I am not sure why these modes are not working. I tried for Listening mode also but it is not working.
Regards