microReticulumTbeam/exercises/07_SD_Startup_Watcher/README.md

Exercise 07: SD Startup Watcher

This exercise is derived from Exercise 05 and keeps that original exercise intact. The focus here is isolating reusable SD startup and hot-insert watcher logic into a library-style structure.

This exercise now has two parts:

1. A reusable SD startup/watcher library in lib/startup_sd.
2. A harness app in src/main.cpp that demonstrates how to use that library.

Watcher behavior:

1. Initializes PMU and enables SD power rail (AXP2101 BLDO1).
2. Polls for card changes with debounced state transitions.
3. Emits events only on change:
   • EVENT: card inserted/mounted
   • EVENT: card removed/unavailable
   • EVENT: no card detected
4. On mount event, emits callback status (SdEvent) and runs SD write workflow.
5. Every 15 seconds while mounted, runs a periodic write/permission check.
6. Uses fast preferred probe (HSPI @ 400k) and occasional full fallback scan.

Status callback usage:

• SdEvent::NO_CARD -> show "Missing SD card / Please insert card to proceed"
• SdEvent::CARD_MOUNTED -> card ready
• SdEvent::CARD_REMOVED -> card removed, wait for insert

Files used in this exercise:

• /Exercise_07_test.txt
• /test/testsub1/testsubsub1/Exercise_07_test.txt

Build

source /home/jlpoole/rnsenv/bin/activate
pio run -e node_a

Upload

source /home/jlpoole/rnsenv/bin/activate
pio run -e node_a -t upload --upload-port /dev/ttyACM0

Monitor

screen /dev/ttyACM0 115200