LibreVNA/FPGA
Roger Henderson 1ea012aa57 implement FPGA-based CDS to avoid BRAM overflow
Move CDS phase computation from per-point config storage to FPGA logic.
The FPGA now computes the 180° phase shift internally (M/2) and loops
twice per point when CDS is enabled. This keeps config memory at 96 bits
instead of 112, avoiding BRAM overflow on the Spartan 6.

FPGA changes:
- Add CDS_ENABLED input to Sweep module (controlled via SPI register 6)
- Compute source_phase = M/2 for 180° shift when cds_phase=1
- State machine loops through all stages twice per point when CDS enabled
- RESULT_INDEX now includes cds_phase bit: stage[2:0] & point[11:0] & cds_phase

Firmware changes:
- Add FPGA::SetCDSEnabled() to control CDS via register 6 bit 11
- Update SamplingResult to include cdsPhase field (1 bit)
- Simplify VNA.cpp: FPGA handles phase switching, MCU combines results

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>
2026-02-01 21:19:57 +13:00
..
Generator/ipcore_dir WIP: device synchronization 2022-08-07 03:01:22 +02:00
VNA implement FPGA-based CDS to avoid BRAM overflow 2026-02-01 21:19:57 +13:00
.gitignore Window coefficient files added 2020-10-29 20:07:41 +01:00
AMAttenuationCalculator.py WIP: device synchronization 2022-08-07 03:01:22 +02:00
WindowCoefficientGenerator.py Window coefficient files added 2020-10-29 20:07:41 +01:00