Hardware documentation improvements

Preamble

After checking out portapack I got quite an inspiration to use hackrf portably. Since hackrf doesn't have powerful enough hardware to do for example digital voice processing, it has to be done on the external hardware.
I would like to keep it as portable as possible and this means not using usb, but instead hackrf's motherboard headers.

I am, to say at least, not an expert in modern electronics. Devices like hackrf, raspberry pi and some arduino-like boards, are my toys on the way to proper understanding, but it contributes to a lot of questions.

Main problem

Hardware documentation and especially pin headers usage lacks information about my use case. Things that would be cool to see:

• More information about pins. ADC0_2, VBUSCTRL, WAKEUP, VBAT(hackrf doesn't have battery), B1AUX13, BANK2F3M2 are making me confused 😅.
• What each major part actually does.

Actual questions

For some of them there are conjectures in my brain but it would cool to clarify them and maybe help create hardware FAQ section in documentation.

1. What should be done to start rx or tx operation? Is just passing signals to ADC/DAC on P9 header enough?
2. How can RF gains, baseband filter and sampling rate be set trough pin headers?
3. What is CPLD used for in hackrf? (i actually don't know what it's practical applications in general and have hard time understanding)
4. How does mixer rated to such wide frequency range work with transceiver rated only to 2.3-2.7ghz?
5. What is the proper way to supply power for hackrf trough pin headers and where can be power taken on hackrf to supply it to pheripherials?

Start by reviewing the existing hardware documentation for the pin headers, especially P9, and the listed signals such as ADC0_2, VBUSCTRL, WAKEUP, and VBAT. Trace the questions about CPLD, mixer, transceiver, RF control, and power connections, then define the documentation sections or FAQ entries needed to answer them.