33 lines
1.2 KiB
Markdown
33 lines
1.2 KiB
Markdown
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## Exercise 11: Set RTC to GPS (1PPS Discipline)
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This exercise extends Exercise 9 behavior (GPS + SD + OLED) and disciplines the onboard RTC from GPS UTC using the GPS `1PPS` (pulse-per-second) timing signal.
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Implemented behavior:
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1. Boots PMU, OLED, SD watcher, and GPS UART using the same T-Beam Supreme pin mapping from prior exercises.
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2. Parses NMEA (`RMC`, `GGA`, `GSV`) to track UTC validity and satellite counts.
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3. Every 1 minute, attempts to set RTC from GPS:
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- Uses latest valid GPS UTC.
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- Waits for next `1PPS` rising edge.
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- Sets RTC to GPS time aligned to that edge (UTC + 1 second).
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4. Appends event records to SD file:
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- Path: `/gps/discipline_rtc.log`
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- Append-only writes (`FILE_APPEND`)
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- Format:
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- `YYYYMMDD_HH24MISS_z\t set RTC to GPS using 1PPS pulse-per-second discipline\trtc-gps drift=+/-Ns`
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5. OLED success message shows RTC disciplined confirmation and timestamp.
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6. If GPS time cannot be determined (or 1PPS edge is not seen in timeout), OLED shows failure status and the loop delays 30 seconds before retry.
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## Build
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```bash
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source /home/jlpoole/rnsenv/bin/activate
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pio run -e node_a
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```
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## Upload
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```bash
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source /home/jlpoole/rnsenv/bin/activate
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pio run -e node_a -t upload --upload-port /dev/ttyACM0
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```
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