Troubleshooting

Chip does not respond

• verify wiring and voltage levels
• verify CS pin selection
• lower SPI clock and retest
• ensure begin() is called before IO

Write failures

• erase flash region before writing
• disable HIGHSPEED while debugging
• check address boundaries and overflow configuration

Intermittent behavior

• verify shared SPI bus ownership
• verify board-core transaction compatibility
• enable diagnostics and capture error code sequence