Microsoft Surface Pro 3 keyboard stopped working after firmware update

Hello there,
I have a surface pro 3 running windows 10. My surface type keyboard stopped working after a FW update. Now the keyboard is not even detected neither in device manager nor in the BIOS. Flashing the BIOS with older FW may solve the problem.
Can any kind hearted person please tell me how should I go about it. To be specific:
1. Where to find an older BIOS image for SP 3?
2. How do I flash the existing BIOs and push the old FW?

Thanks in advance