# Lappy v0.7.4 receiver diagnostics candidate

Builds on v0.7.3 with better handling and diagnosis of Dragy telemetry and rate configuration. The existing Dragy Pro FD03 challenge/response, subscription and CCCD verification remain unchanged. DRG70/DRG70-C and Lite support remains provisional.

- **UBX messages:** validates complete messages with payloads up to 512 bytes. Other valid messages are skipped as complete units; only checksum-valid 92-byte NAV-PVT produces GPS samples. Unknown valid payloads within that bound cannot inject a nested NAV-PVT frame into timing.
- **25 Hz setup:** reports command request, Bluetooth delivery, matching receiver ACK/NAK and measured receiver cadence separately. A NAK retains the actual stream. A missing ACK permits cadence confirmation, preserving the existing Pro behavior. Configuration stays RAM only.
- **Receiver identity:** logs bounded model/firmware values as readable text and exact hex prefixes, plus FD01–FD04 properties. Firmware reads are optional and follow rate setup so a slow identity read cannot postpone the rate request.
- **GPS diagnosis:** `status` and `diag` include `GPS_PROTOCOL` and `GPS_QUALITY` counters for other UBX traffic, checksum/length errors, configuration replies and overlapping sample rejection reasons. Position, accuracy, UTC and timing acceptance requirements are retained.

Software validation includes bounded parser/reply tests, 69 production BLE worker scenarios, the public-export-inspired regression, full host regression checks with ASan/UBSan, five simulator suites, the V2 target build and linked ATT/stack audits. The signed package is verified with the updater's production trust anchor.

This candidate has not been flashed or tested with a physical receiver. Pro radio regression and DRG70/Lite hardware acceptance remain required. See [implementation details](IMPLEMENTATION_v0.7.4.md) and [hardware scope](HARDWARE_BENCH_v0.7.4.md).