r82xx: improved tuning speed and accuracy #6

Merged

steve-m merged 3 commits from sultanqasim/rtl-sdr:upstream_fast_retune into master

2024-03-08 20:18:37 +00:00

sultanqasim commented

2024-03-07 23:00:31 +00:00

Contributor

Avoid register writes when there is no change to the value, batch writes to adjacent registers during tuning to reduce the number of operations, and use Oliver Jowett's VCO divisor calculation.

Avoid register writes when there is no change to the value, batch writes to adjacent registers during tuning to reduce the number of operations, and use [Oliver Jowett's VCO divisor calculation](https://github.com/steve-m/librtlsdr/pull/10).

sultanqasim added 3 commits 2024-03-07 23:00:32 +00:00

f5978e8871 r82xx: improve tuner precision

Improve tuner precision by calculating the VCO divisor at full precision, not
at kHz resolution. Also replace the manual divison loop with a simpler
fixed-point calculation.

0b64f07fd5 r82xx: avoid redundant register writes for speed

2acb75cff3 r82xx: batch register writes for tuning

Batch six register writes into a single step to speed up retuning.

sultanqasim commented

2024-03-07 23:09:31 +00:00

Author

Contributor

These changes reduce retuning time between nearby frequencies from around 51 ms to around 26 ms.

I also have some potentially more controversial or less well understood changes to further speed up tuning here, in case people are curious. With that branch, retuning time is reduced to 5 ms, which allows quite fast frequency sweeps.

These changes reduce retuning time between nearby frequencies from around 51 ms to around 26 ms. I also have some potentially more controversial or less well understood changes to further speed up tuning [here](https://gitea.osmocom.org/sultanqasim/rtl-sdr/src/branch/fast_retune), in case people are curious. With that branch, retuning time is reduced to 5 ms, which allows quite fast frequency sweeps.