Arduino

Timing Traps

• delay() blocks everything — nothing else runs, no input reading, no interrupts serviced
• millis() for non-blocking timing — compare against last action time
• millis() overflows after ~50 days — use subtraction: millis() - lastTime >= interval
• Interrupts for time-critical events — attachInterrupt() responds immediately

Memory Constraints

• Uno has only 2KB RAM — large arrays fail silently with weird behavior
• F() macro keeps strings in flash — Serial.println(F("text")) saves RAM
• PROGMEM for constant arrays — keeps data out of RAM
• String class fragments heap — prefer char arrays for stability

Serial Debugging

• Baud rate must match — mismatch shows garbage, not an obvious error
• Serial.begin() required in setup — output before this goes nowhere
• Serial printing slows execution — remove or reduce for production code

Upload Problems

• Wrong board selected — uploads but doesn't run correctly
• Serial Monitor holds port — close before uploading
• USB cable might be power-only — some cheap cables don't carry data
• Bootloader corrupted — reflash using another Arduino as ISP

Sensor Communication

• I2C devices share bus — check for address conflicts with scanner sketch
• 5V sensors on 3.3V boards give wrong readings or damage — check operating voltage
• SPI needs separate CS per device — can't share chip select lines

Converted and distributed by TomeVault Context snippets also available to append to your CLAUDE.md, GEMINI.md, and copilot-instructions.md — download at TomeVault