Detailed Wiring Guide
Complete instructions for connecting the Arduino, MAX3232 level converter, Nextion display, and FTDX-10 radio.
Safety First
- Disconnect power before making any connections
- Double-check polarity on all power connections
- Verify voltage levels before connecting components
- Use proper gauge wire for power connections
- Ensure good ground connections throughout
Component Overview
1. Arduino Mega 2560
Serial Ports Used:
- Serial (USB): Debug output and programming
- Serial1 (TX1/RX1): CAT communication with radio
- Serial2 (TX2/RX2): Communication with Nextion display
Pin Assignments:
Pin 18 (TX1) - Transmit to MAX3232
Pin 19 (RX1) - Receive from MAX3232
Pin 16 (TX2) - Transmit to Nextion
Pin 17 (RX2) - Receive from Nextion
5V - Power for MAX3232 and Nextion
GND - Common ground2. MAX3232 Level Converter
Purpose: Converts Arduino TTL levels (0-5V) to RS232 levels (+/-12V)
Typical Module Pinout:
VCC - 5V power input
GND - Ground
T1_IN - TTL input from Arduino TX
T1_OUT - RS232 output to radio RX
R1_IN - RS232 input from radio TX
R1_OUT - TTL output to Arduino RX
Note: Some modules may have different labels (TXD → T1_IN, RXD → R1_OUT)
3. Nextion NX4832K035 Display
4-Wire Connection:
Red - +5V power
Black - Ground (GND)
Blue - RX (receives from Arduino TX2)
Yellow - TX (transmits to Arduino RX2)4. FTDX-10 RS232 Port
DB9 Female Connector (rear panel):
Pin 1: Not connected
Pin 2: RXD (Input to radio)
Pin 3: TXD (Output from radio)
Pin 4: Not connected
Pin 5: GND (Signal ground)
Pins 6-9: Not connectedStep-by-Step Wiring Instructions
Step 1: Power Connections
Option A: USB Power (Easiest for testing)
Computer USB → Arduino USB port- Good for initial testing
- Limited current capacity (500mA)
- Not suitable for permanent installation
Option B: External 5V Power Supply (Recommended)
5V Power Supply (+) → Arduino VIN (or 5V pin)
5V Power Supply (-) → Arduino GND- Recommended for permanent installation
- Minimum 1A supply recommended
- Use regulated 5V supply
Option C: DC Barrel Jack
7-12V Power Supply → Arduino DC barrel jack- Use 7-12V regulated supply
- Arduino onboard regulator handles conversion
- Generates some heat
Step 2: Connect MAX3232 to Arduino
Power Connections:
Arduino 5V → MAX3232 VCC
Arduino GND → MAX3232 GNDData Connections:
Arduino Pin 18 (TX1) → MAX3232 T1_IN (or TXD)
Arduino Pin 19 (RX1) → MAX3232 R1_OUT (or RXD)Wire Recommendations:
- Use solid core 22 AWG wire for breadboard
- Use stranded 22-24 AWG for permanent installation
- Keep data wires away from power wires
- Twist TX/RX pairs together to reduce noise
Step 3: Connect MAX3232 to Radio
Make RS232 Cable
You'll need:
- DB9 Female connector (solder type or crimp)
- 3-conductor shielded cable
- Heat shrink tubing
Cable Wiring:
MAX3232 T1_OUT → DB9 Pin 2 (Radio RXD)
MAX3232 R1_IN → DB9 Pin 3 (Radio TXD)
MAX3232 GND → DB9 Pin 5 (Radio GND)
Important:
- This is a straight-through cable, NOT null-modem
- Use shielded cable to reduce interference
- Keep cable length under 10 feet (3 meters)
- Connect shield to GND at ONE end only (radio end)
DB9 Connector Numbering:
Looking at pins (solder side):
5 4 3 2 1
9 8 7 6
Looking at connector (front):
1 2 3 4 5
6 7 8 9Step 4: Connect Nextion Display
Direct Connection to Arduino:
Nextion Red (5V) → Arduino 5V
Nextion Black (GND) → Arduino GND
Nextion Blue (RX) → Arduino Pin 16 (TX2)
Nextion Yellow (TX) → Arduino Pin 17 (RX2)Wire Length:
- Keep display wires under 3 feet (1 meter) if possible
- Use 22-24 AWG stranded wire for flexibility
- Can use standard jumper wires for testing
Display Mounting:
- Display draws approximately 150-200mA
- Ensure solid connections (vibration can cause issues)
- Consider panel-mount solution for permanent install
Step 5: Ground Connections
Critical: All grounds must be connected together!
Arduino GND ─┬─ MAX3232 GND
├─ Nextion GND
├─ Radio GND (DB9 Pin 5)
└─ Power Supply GNDGround Loop Prevention:
- Use a star ground configuration if possible
- Connect shield of RS232 cable to ground at radio end only
- If experiencing noise, try ferrite beads on cables
Verification and Testing
Visual Inspection Checklist
Before applying power:
- All power connections are correct (5V to 5V, GND to GND)
- No short circuits between power and ground
- TX and RX connections are not swapped
- DB9 connector pins are correct
- All solder joints are solid (if applicable)
- No loose wires
- Proper wire gauge used throughout
Initial Power-On Test
- Disconnect radio cable (test Arduino and display first)
- Power on Arduino
- Check 5V LED on Arduino is lit
- Check MAX3232 power LED (if present)
- Check Display
- Display should power on and show startup screen
- If blank, check power connections
- If garbage, check serial connections
- Connect USB and Check Serial Monitor
Arduino IDE → Tools → Serial Monitor Set baud rate to 115200 Should see: "FTDX-10 Controller Starting..." - Connect radio cable
- Power on FTDX-10 radio
- Wait 5 seconds
- Should see frequency appear on display
Troubleshooting Test Points
Voltage Measurements (Power ON):
| Location | Expected | Tolerance |
|---|---|---|
| Arduino 5V pin | 5.0V | ±0.25V |
| MAX3232 VCC | 5.0V | ±0.25V |
| Nextion red wire | 5.0V | ±0.25V |
Continuity Tests (Power OFF):
| Between | Expected |
|---|---|
| Arduino GND ↔ MAX3232 GND | 0Ω |
| Arduino GND ↔ Nextion GND | 0Ω |
| Arduino GND ↔ Radio GND | 0Ω |
Common Wiring Mistakes
| Mistake | Symptom | Fix |
|---|---|---|
| Swapped TX/RX | No communication | Swap TX and RX connections |
| Wrong Baud Rate | Garbage data | Check baud rates in code and radio |
| Missing Ground | Erratic behavior | Connect all grounds together |
| Null-Modem Cable | Radio doesn't respond | Use straight-through cable |
| Wrong MAX3232 Pins | No RS232 communication | Verify T1_IN/T1_OUT, R1_IN/R1_OUT |
Professional Installation Tips
Enclosure Considerations
Panel Cutouts:
- Nextion display: 93mm x 70mm rectangular cutout
- USB access for Arduino programming
- DB9 connector mounting hole
- Power input jack
- Ventilation holes
Component Mounting:
- Use standoffs for Arduino to prevent shorts
- Secure MAX3232 module with adhesive or standoffs
- Mount display with screws and gasket
- Strain relief for all cables
Cable Management
- Use cable ties to secure wiring
- Route power and signal cables separately
- Label all connections
- Use color-coded wires:
- Red: +5V
- Black: Ground
- Yellow/White: TX signals
- Blue/Green: RX signals
EMI/RFI Considerations
For HF radio use:
- Use ferrite cores on cables
- Keep wiring away from antenna connections
- Shield enclosure if possible
- Use shielded cables for RS232
- Ensure good grounding
Ferrite Placement:
- Place on USB cable near Arduino
- Place on RS232 cable near radio
- Place on display power cable
- Use Type 43 material ferrites
Permanent Installation Diagram
┌─────────────────────────────────────────────┐
│ FTDX-10 CONTROLLER │
│ │
│ ┌───────────────┐ ┌─────────────┐ │
│ │ NEXTION │ │ ARDUINO │ │
│ │ DISPLAY │◄───────►│ MEGA │ │
│ │ NX4832K035 │ 4-wire │ 2560 │ │
│ └───────────────┘ └─────────────┘ │
│ ▲ │ │
│ │ │ │
│ │ 5V/GND │ Serial │
│ │ ▼ │
│ ┌──────┴─────────────────┬──────────────┐ │
│ │ │ MAX3232 │ │
│ │ 5V POWER SUPPLY │ LEVEL │ │
│ │ │ CONVERTER │ │
│ └────────────────────────┴──────────────┘ │
│ │ │
│ │ RS232 │
└──────────────────────────────────┼──────────┘
│
▼
┌─────────────────┐
│ YAESU FTDX-10 │
│ DB9 RS232 │
└─────────────────┘Testing Procedure Summary
- Visual inspection of all connections
- Continuity test all grounds (power off)
- Voltage test all power connections (power on, radio disconnected)
- Test Arduino USB serial output
- Test Nextion display response
- Connect radio and verify CAT communication
- Test all control functions
- Verify TX/RX operation (at low power!)
Always double-check connections before applying power!
If you're unsure about any wiring, consult with an experienced electronics technician or amateur radio operator.