## Exercise 06: RTC Check (PCF8563)

Time is always Greenwich Mean Time ("Zulu")

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.
