Setting RTC to GPS with 1PPS precision working. Here is an example log:

20260217_200901_z	 set RTC to GPS using 1PPS pulse-per-second discipline	rtc-gps drift=-28 s
20260217_201001_z	 set RTC to GPS using 1PPS pulse-per-second discipline	rtc-gps drift=+0 s
20260217_201119_z	 set RTC to GPS using 1PPS pulse-per-second discipline	rtc-gps drift=+0 s
20260217_201219_z	 set RTC to GPS using 1PPS pulse-per-second discipline	rtc-gps drift=+0 s

exercises/11_Set_RTC2GPS/README.md

@@ -0,0 +1,33 @@
+## Exercise 11: Set RTC to GPS (1PPS Discipline)
+
+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.
+
+Implemented behavior:
+
+1. Boots PMU, OLED, SD watcher, and GPS UART using the same T-Beam Supreme pin mapping from prior exercises.
+2. Parses NMEA (`RMC`, `GGA`, `GSV`) to track UTC validity and satellite counts.
+3. Every 1 minute, attempts to set RTC from GPS:
+   - Uses latest valid GPS UTC.
+   - Waits for next `1PPS` rising edge.
+   - Sets RTC to GPS time aligned to that edge (UTC + 1 second).
+4. Appends event records to SD file:
+   - Path: `/gps/discipline_rtc.log`
+   - Append-only writes (`FILE_APPEND`)
+   - Format:
+     - `YYYYMMDD_HH24MISS_z\t set RTC to GPS using 1PPS pulse-per-second discipline\trtc-gps drift=+/-Ns`
+5. OLED success message shows RTC disciplined confirmation and timestamp.
+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.
+
+## Build
+
+```bash
+source /home/jlpoole/rnsenv/bin/activate
+pio run -e node_a
+```
+
+## Upload
+
+```bash
+source /home/jlpoole/rnsenv/bin/activate
+pio run -e node_a -t upload --upload-port /dev/ttyACM0
+```