Breadboard layout

🎛️ Wire Color Key

• Red → +12 V input
• Orange → +5 V regulated
• Black → Ground
• Yellow → MIDI signal lines (raw + clean)
• Blue → Logic connections (inverter inputs/outputs)
• Green → LED wiring
• White → Misc short links / regulator wiring

🧱 FULL STEP‑BY‑STEP ASSEMBLY

1. Build the 12 V → 5 V Regulator Block

Place the 78L05

Flat face toward you:
(1) IN — (2) GND — (3) OUT

Wire the input

• Red wire: 12 V → 1N4007 → 78L05 pin 1
• Black wire: 12 V ground → GND rail

Add capacitors

• 100 µF: 78L05 pin 1 → GND
• 10 µF: 78L05 pin 3 → GND
• 100 nF: 78L05 pin 3 → GND

Create rails

• Orange wire: 78L05 pin 3 → +5 V rail
• Black wire: 78L05 pin 2 → GND rail

2. Add the 5 V Power‑On LED

Place this near the regulator block.

• Green wire: +5 V rail → 1 kΩ resistor → LED anode
• LED cathode → Black wire → GND

This LED lights whenever the regulator is producing 5 V.

3. Place the ICs

• 6N138 left‑center, straddling the trench
• 74HC14 right‑center, straddling the trench

4. Power the ICs

• Orange wire: 6N138 pin 8 → +5 V
• Black wire: 6N138 pin 5 → GND
• Orange wire: 74HC14 pin 14 → +5 V
• Black wire: 74HC14 pin 7 → GND

Pull‑up

• 10 kΩ: 6N138 pin 6 → +5 V (orange)

5. Place and Wire the MIDI IN Header

Header pin mapping:

• Pin 1 = DIN pin 4
• Pin 2 = DIN pin 5
• Pin 3 = DIN pin 2 (GND)

Wire it

• Yellow wire: IN pin 1 → 220 Ω → 6N138 pin 2
• Yellow wire: IN pin 2 → 6N138 pin 3
• Black wire: IN pin 3 → GND

Protection diode

• Between 6N138 pins 2 and 3
• Stripe toward pin 2

6. Connect 6N138 Output to 74HC14 and MatrixPortal RX

• Yellow wire: 6N138 pin 6 → 74HC14 pin 1
• Blue wire: 74HC14 pin 2 → MatrixPortal RX

⭐ Important clarification:

74HC14 pin 2 is the “clean MIDI” signal.
All THRU inverter inputs will connect to this exact pin.

7. Connect ALL THRU Inverter Inputs to 74HC14 Pin 2

Use blue wires to tie each inverter input to the clean MIDI node at pin 2:

• 74HC14 pin 3 → pin 2
• 74HC14 pin 5 → pin 2
• 74HC14 pin 9 → pin 2
• 74HC14 pin 11 → pin 2

This means:

Pin 2 is the single source feeding all four THRU inverters.

8. Add THRU/OUT Activity LED

This LED shows the buffered MIDI signal feeding all THRUs and your internal OUT.

• Green wire: 74HC14 pin 2 → 1 kΩ → LED anode
• LED cathode → Black wire → GND

9. Place THRU Headers (THRU1–4)

Each header:

• Pin 1 = DIN pin 4 (from +5 V via 220 Ω)
• Pin 2 = DIN pin 5 (from inverter output via 220 Ω)
• Pin 3 = DIN pin 2 (GND)

Place them along the bottom right of the breadboard.

10. Wire THRU Outputs

THRU1 (inverter B)

• Blue wire: 74HC14 pin 4 → 220 Ω → THRU1 pin 2
• Orange wire: +5 V → 220 Ω → THRU1 pin 1
• Black wire: THRU1 pin 3 → GND

THRU2 (inverter C)

• Blue wire: 74HC14 pin 6 → 220 Ω → THRU2 pin 2
• Orange wire: +5 V → 220 Ω → THRU2 pin 1
• Black wire: THRU2 pin 3 → GND

THRU3 (inverter D)

• Blue wire: 74HC14 pin 8 → 220 Ω → THRU3 pin 2
• Orange wire: +5 V → 220 Ω → THRU3 pin 1
• Black wire: THRU3 pin 3 → GND

THRU4 (inverter E)

• Blue wire: 74HC14 pin 10 → 220 Ω → THRU4 pin 2
• Orange wire: +5 V → 220 Ω → THRU4 pin 1
• Black wire: THRU4 pin 3 → GND

11. Internal MIDI OUT (No DIN Jack)

Use the last inverter (F):

• Yellow wire: MatrixPortal TX → 74HC14 pin 13
• Blue wire: 74HC14 pin 12 → internal OUT node (your choice)

This gives you a clean, buffered logic‑level MIDI OUT.