What does v2 in px4fmu-v2 firmware stand for?

I have pixhawk hardware. I know pixhawk hardware is px4 fmu + px4 io.

As per what I studied at link px4 fmu contains the arm cortex m4f chip which will have the autopilot firmware. px4 io is the input output module.

So when I installed px4 firmware on my pixhawk I saw px4fmu-v2 version being downloaded. What does v2 stand for? Is it version of firmware for pixhawk or is it version of fmu chip in pixhawk

px4fmu-v2 is a “board configuration”. One example of a board which uses this configuration is the 3DR Pixhawk http://dev.px4.io/hardware-pixhawk.html

Thanks @Mark_Whitehorn for the reply. What do you mean by ‘board configuration’?

And I did searched a bit more. According to https://groups.google.com/forum/#!topic/px4users/lk3Tz5F2cRI it looks like v2 is version 2 of px4fmu which is used in pixhawk. So v1 for 1.6/1.7 px4fmu and v2 for fused px4fmu anf px4 io present in pixhawk. What do you think?

There is a board configuration for each version of hardware. Each different hardware target has its own configuration which deals with board-specific items such as I/O pin assignments. To port PX4 to a new board, you create a new configuration and associated build target for the firmware.