RTC keeps time between POWER OFF & ON, SD Card at start still needs work -- if card is in the slot, it is not readable until it is pulled on and then inserted.

exercises/06_RTC_check/README.md

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+## Exercise 06: RTC Check (PCF8563)
+
+This exercise validates RTC read/write and power-off persistence on the T-Beam Supreme.
+
+It:
+- Initializes PMU + I2C bus used by RTC.
+- Reads RTC at startup.
+- Prints RTC every 10 seconds.
+- Accepts serial commands:
+  - `show`
+  - `set YYYY-MM-DD HH:MM:SS`
+  - `help`
+
+## 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
+```
+
+## Monitor
+
+```bash
+screen /dev/ttyACM0 115200
+```
+
+## Suggested Persistence Test
+
+1. Set the RTC:
+   - `set 2026-02-14 17:30:00`
+2. Confirm:
+   - `show`
+3. Power off the unit for a few minutes.
+4. Power on and run:
+   - `show`
+5. Compare expected elapsed time vs RTC output.