perf(battery): increase gauge sleep measurement intervals to 60 seconds

[TobiasRoeddiger]

The BQ27220 periodically measures while the earable is off. Set its SLEEP voltage/temperature and current measurement intervals to 60 seconds instead of the 20-second defaults, reducing the measured average off-state current by about 1.6–1.9 µA (4–5%).

This adds only the two adjacent one-byte settings at 0x921E and 0x921F to the existing gauge setup transaction. Normal-mode measurement timing is unchanged. Sleep readings update less frequently, so changes detected through those measurements can take longer to appear. The standard FOTA configuration applies gauge setup when confirming a new image.

Power validation

Rechecked the archived raw PPK2 captures and their SHA-256 hashes before creating this PR:

Comparison	20-second intervals	60-second intervals	Saving
Matched 240-second windows	38.055 µA	36.180 µA	1.874 µA (4.93%)
Repeat, matched 120-second windows	38.085 µA	36.476 µA	1.609 µA (4.22%)

The sequence was 60 s → restored 20 s → repeated 60 s. Same Main v2.7 device, PPK2 source at 3.7 V replacing the battery, device USB disconnected, 100 ksample/s and matching filter settings. All samples, including measurement pulses, contribute to the means. The MCU entered OFF without an active debugger; retained journals were complete and recorded no spontaneous application wakes. Full captures were saved before endpoint debug access.

These measurements used the P0.6-fixed diagnostic reference firmware with the interval bytes changed in gauge RAM and read back. They establish the saving from the settings; they are not measurements of this PR's firmware binary. The P0.6 change is released separately as 2.2.9 in #294 (original fix: #290). No other gauge configuration changes are included here.

Registers and sleep sampling behavior: TI BQ27220 technical reference manual, data-memory table and §§4.9.54–4.9.55.

Build validation

• Clean FOTA sysbuild passed for openearable_v2/nrf5340/cpuapp using nRF Connect SDK 3.0.1 (-DFILE_SUFFIX=fota, explicit worktree BOARD_ROOT).
• Compiled driver inspection confirms a two-byte 3c 3c write at 0x921E.
• git diff --check passed.

This PR now targets 2.2.10; it remains limited to the same six added driver lines. Historical build and power results above predate the release-branch reorganization.

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✅ Unit tests passed

2 passed, 0 failed/error, 0 skipped — view workflow run

Test scenario	Platform	Result
sensor_component/openearable.unit.sensor_component	native_sim/native/64	✅ passed
ring_buffer/openearable.unit.ring_buffer	native_sim/native/64	✅ passed

Download the unit-test-results artifact for full Twister reports and logs.

[github-actions]

Build output available:
openearable_v2_firmware.elf.zip
openearable_v2_fota.zip

[github-actions]

Compiler warnings

The extended-warning build completed successfully.

Application compiler warnings

None.

View this workflow run

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CodeChecker static analysis (advisory)

Note

This report is informational. It does not block merging and does not change code.

At a glance

Scope	Result
Findings on lines changed by this PR	0
Findings in the complete codebase	2
Analyzer invocations completed	162
Analyzer invocations failed	0

Findings on changed lines

No non-style findings were reported on lines changed by this PR.

Analyzer coverage

Analyzer	Completed	Failed
clangsa	81	0
cppcheck	81	0

Complete-codebase summary

Severity: 2 high
Reported by analyzer: clangsa: 2

Complete-codebase findings

Each finding includes source context. The > line and carets identify the expression reported by the analyzer.

Show detailed findings with source context (2 of 2)

HIGH — src/SensorManager/BMX160/bosch/bmi160.c:2507 — The left operand of '&' is a garbage value

  2506 |             /* Set the FOC config for gyro */
> 2507 |             data = BMI160_SET_BITS(data, BMI160_GYRO_FOC_EN, foc_conf->foc_gyr_en);
       |                    ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  2508 | 

HIGH — src/SensorManager/BMX160/bosch/bmi160.c:5492 — The left operand of '&' is a garbage value

  5491 |     rslt |= bmi160_get_regs(addr, data, 2, dev);
> 5492 |     data[1] = data[1] & BMI160_FIFO_BYTE_COUNTER_MASK;
       |               ^^^^^^^
  5493 | 

Open the workflow run and download the complete CodeChecker report for a detailed view. Check out codechecker.html/index.html.

[github-actions]

Build output available:
openearable_v2_firmware.elf.zip
openearable_v2_fota.zip