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docs: BUG-18 DS3231 installed + working (I²C 0x68), pending power-cycle test

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Mathieu Moran
2026-08-14 18:05:17 -04:00
parent c2462356e1
commit bfdd1c2285
2 changed files with 14 additions and 4 deletions
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BUGS.md
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@@ -19,10 +19,19 @@ When CLOSED, move the entire entry to Resolved — don't duplicate.
timestamp jump mid-trip. Root cause is BUG-18. timestamp jump mid-trip. Root cause is BUG-18.
### BUG-18 — Pi needs offline timekeeping (no RTC) ### BUG-18 — Pi needs offline timekeeping (no RTC)
- **Status**: `OPEN` 2026-08-13 - **Status**: `IN PROGRESS` 2026-08-14
- **Phase**: 29 - **Phase**: 29
- **Problem**: the Pi 3 has no real-time clock. Without internet (no NTP) the system clock - **Problem**: the Pi 3 has no real-time clock. Without internet (no NTP) the system clock
is wrong across power cycles, corrupting tracking/trip timestamps (BUG-16/BUG-17). is wrong across power cycles, corrupting tracking/trip timestamps (BUG-16/BUG-17).
- **Progress 2026-08-14**: DS3231 module installed + working. Pi config done:
`dtparam=i2c_arm=on` + `dtoverlay=i2c-rtc,ds3231` in `/boot/firmware/config.txt`,
`i2c-tools` installed, `fake-hwclock` disabled, `i2c-dev` added to `modules-load.d`.
The DS3231 now probes at `0x68` (`UU`), its 24C32 EEPROM at `0x57`, `/dev/rtc0` registered,
and `hwclock -r` matches system time. (First scan was an empty bus — a data-line wiring
issue, since resolved.)
**Pending**: power-cycle persistence test — unplug, replug, confirm correct time at boot
without NTP. Also: the charge diode was re-added during debugging and must be removed again
for the CR2032.
- **Fix plan (both, they complement each other)**: - **Fix plan (both, they complement each other)**:
1. **DS3231 RTC module (primary)** — battery-backed RTC on the free I²C bus (SDA pin 3, 1. **DS3231 RTC module (primary)** — battery-backed RTC on the free I²C bus (SDA pin 3,
SCL pin 5, 3.3V pin 1, GND pin 6). Enable `dtparam=i2c_arm=on` + SCL pin 5, 3.3V pin 1, GND pin 6). Enable `dtparam=i2c_arm=on` +
PLAN.md
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@@ -2273,11 +2273,12 @@ logged as `BUG-XX` entries in [BUGS.md](./BUGS.md) (BUG-16 onward) and fixed + v
across reboots; also fixed a NULL-GPS speed-only row crash in the trip builder. Verified the across reboots; also fixed a NULL-GPS speed-only row crash in the trip builder. Verified the
2026-08-13 drive now appears locally. 2026-08-13 drive now appears locally.
- **BUG-17 (trip timestamps wrong) — OPEN**: no RTC → clock drifts without internet. - **BUG-17 (trip timestamps wrong) — OPEN**: no RTC → clock drifts without internet.
- **BUG-18 (no RTC) — OPEN**: plan set — DS3231 RTC on I²C (desolder charging circuit, CR2032) - **BUG-18 (no RTC) — 🚧 IN PROGRESS**: DS3231 installed + configured + detected on I²C (`0x68`),
+ SIM868 CR1220 RTC backup; NTP online, RTC/GNSS fallback offline. `hwclock` reads correct time; `fake-hwclock` disabled; `i2c-dev` persisted. Pending the
power-cycle persistence test. Secondary: SIM868 CR1220 RTC backup still to install.
Open items from the drive — fill in as reported: Open items from the drive — fill in as reported:
- BUG-17 / BUG-18 (clock) pending. - BUG-17 (clock) — blocked on BUG-18 power-cycle verification.
## Working Notes / Environment Gotchas ## Working Notes / Environment Gotchas