Radio configuration register interface

[mossmann]

This implements a new firmware API for unified control of the radio section with a register interface. Requested configuration changes are written to the active register bank. Settings in the active bank are periodically applied and written to the applied bank. Additional banks for specific operating modes store settings that will be copied to the active bank and then applied when switching to that operating mode. For example, settings in the RX bank are copied and applied when starting RX. This effectively implements most of #906.

This initial implementation replaces the underlying structure without changing function from the perspective of host software. It aims to enable future work:

• Make all radio settings retrievable by the host. (Some of this is already done, but additional work will enable, for example, retrieval of the precise tuned frequency instead of the requested frequency.)
• Consolidate radio elements under radio.c, moving them out of hackrf_core.c.
• Update libhackrf and documentation to make the register interface useful to host software.
• Implement additional radio configuration modes that use alternative FPGA bitstreams on HackRF Pro.

Additionally, by moving the application of radio configuration changes outside of interrupt handlers, this eliminates a class of concurrency bug that can cause tuning failure or other configuration errors.

Fix #1681
Fix #1683

[antoinevg]

👌 I think this is the elegant solution.

Tested:

• hackrf_debug --selftest
• hackrf_debug read/write registers
• hackrf_transfer tx/rx, verify all settings function
• SDRAngel tx/rx, all settings, verify all settings function

On:

• HackRF One r4
• Praline r1.0
• HackRF Pro 1.2

[martinling]

I was just doing some testing with the rad1o badge, and found that sweep mode has been broken there since commit b1bfc24. I don't know the cause yet.