CSA_OB_READ_FAIL (0x10160bf7) occurring at inconsistent, sometimes high rates across fleet

[piotr063]

Summary

Multiple Kestrel loggers in the "WinterTurf - v3 International" deployment are throwing
CSA_OB_READ_FAIL (I2C error reading the onboard PAC1934 current/power monitor) at
widely varying rates. Discovered while auditing SD-dumped error packets across 6 units
after a firmware/sensor-config update.

Error details

• Code: 0x10160bf7
• Name: CSA_OB_READ_FAIL
• Class: I2C | Hardware: Kestrel | Sub-device: Sensors (CSA)
• Description (per ERRORCODES.md): "Kestrel CSA read failure" — I2C read failure on the
  onboard PAC1934 current sense amplifier

Observed occurrence (most recent error file per device, single SD dump)

Device	Firmware/config status at time of dump	CSA_OB_READ_FAIL count
41_INT	New firmware confirmed	3
53_INT	New firmware confirmed	8
68_INT	New firmware confirmed (recent switch)	27
69_INT	New firmware confirmed (recent switch)	7
79_INT	Old firmware (update hadn't taken)	0
80_INT	Old firmware/config still active	253

Notes

• Occurrence doesn't cleanly correlate with firmware version — 79_INT (old firmware)
  showed zero occurrences while 80_INT (also old firmware) showed the highest count
  of any device. This suggests it may not be a pure firmware regression, but could
  involve per-unit hardware variance (marginal solder joint, bus loading, etc.) as well.
• This error is scoped to the Kestrel's internal power-monitoring chip, not the
  field sensors (soil/CO2/O2) — it affects power/current diagnostic fields
  (PORT_V, PORT_I, AVG_P) rather than environmental data collection.

Ask

• Confirm whether this rate is expected/known, or indicates a driver timing issue
  introduced in a recent firmware release
• If hardware-related: guidance on what would cause read failures specifically on
  the onboard PAC1934 (vs. the field-sensor I2C/SDI-12 buses)
• Recommended threshold (occurrences/day?) above which a unit's CSA chip should be
  considered suspect and inspected/replaced

Reproduction data

SD dumps available on request — pulled via rtgs sd-dump dump --recent 3 per device.