Schematic Notes – DIY 3D Printer (RAMPS 1.4 + Arduino Mega 2560 + TMC2209)

Power System:
- Main PSU: 24V DC input from AC (Live/Neutral).
- A buck converter steps 24V down to 12V and powers the Arduino Mega via the barrel jack (VIN).
- The 24V rail powers motors, hotend, heated bed, and fans.
- 5V logic power is generated by the Arduino Mega’s onboard regulator.

Motor Drivers – TMC2209 (Legacy Mode):
- STEP, DIR, and EN pins are used; no UART communication for now.
- PDN/DIAG left unconnected for future UART upgrade.
- Motors powered by 24V; logic powered by 5V from Mega.
- Dual Z motors use separate TMC2209 drivers but share STEP, DIR, and EN pins.
- MS1/MS2 left floating (defaults used).

Thermistors:
- Hotend thermistor (THERM0) → A13.
- Heated bed thermistor (THERM1) → A14.
- 10k NTC type. RAMPS includes internal pull-up resistors.

Heaters and Fans:
- Hotend heater → D10.
- Heated bed heater → D8.
- Fan0 (hotend cooling) → D9.
- Fan1 added for board/driver cooling.

LCD Display (RRD12864):
- Connected via EXP1 and EXP2 headers.
- Includes SD card and rotary encoder.
- Match wiring to specific display module.

Limit Switches:
- X, Y, Z limit switches wired to MIN pins.
- Normally Open (NO) type. COM → GND, NO → signal.
- Pull-ups handled by firmware or RAMPS.

Labeling and Connections:
- Use clear labels: +24V, +5V, GND.
- VIN not shown on Mega symbol; powered through buck to barrel jack.

Additional Notes:
- PDN/DIAG left unconnected for now.
- EN pins can be shared and labeled "EN".
- Microstepping (MS1/MS2) unused for now.
- PSU symbol uses 4 pins: L, N, +V (24V), GND.

Future Expansion:
- UART mode (connect PDN/DIAG to TX/RX).
- Optional: filament sensor, bed leveling probe, extra fans.
- Add inline fuses, TVS diodes for protection.
- Optional indicator LEDs.

Final Remarks:
- Schematic assumes RAMPS is stacked on the Arduino Mega.
- RAMPS is not shown as a separate symbol; Mega is wired directly.
- Compatible with Marlin firmware (legacy mode).