PICO_LCD16x2_ENCODER

QN8066 with Raspberry Pi Pico, LCD16x2 and Rotary Encoder

This example demonstrates a complete FM transmitter control system using:

• Raspberry Pi Pico as the main controller
• QN8066 FM transceiver
• 16x2 LCD display with I2C backpack
• Rotary encoder with push button for navigation

Circuit Diagram

                    Raspberry Pi Pico
                   ┌───────────────────┐
                   │                   │
             ┌─────┤ 3.3V (36)         │
             │     │                   │
     ┌───────┼─────┤ GND (38)          │
     │       │     │                   │
     │   ┌───┼─────┤ GP0 (1)  SDA      │ ← I2C Bus
     │   │   │     │                   │
     │   │   │ ┌───┤ GP1 (2)  SCL      │ ← I2C Bus
     │   │   │ │   │                   │
     │   │   │ │ ┌─┤ GP2 (4)  ENC_A    │ ← Encoder A
     │   │   │ │ │ │                   │
     │   │   │ │ │ ┌┤ GP3 (5)  ENC_B   │ ← Encoder B
     │   │   │ │ │ ││                  │
     │   │   │ │ │ │┌┤ GP4 (6)  ENC_BTN│ ← Encoder Button
     │   │   │ │ │ │││                 │
     │   │   │ │ │ │││ GP16(21) CEN    │ ← QN8066 Enable
     │   │   │ │ │ │││                 │
     │   │   │ │ │ │││                 │
     │   │   │ │ │ │││                 │
     │   │   │ │ │ │││                 │
     │   │   │ │ │ │││                 │
     │   │   │ │ │ │├┘                 │
     │   │   │ │ │ ├┘                  │
     │   │   │ │ ├┘                    │
     │   │   │ ├┘                      │
     │   │   ├┘                        │
     │   │   │                         │
     │   │   │                         │
     │   │   │    ┌─────────────┐      │
     │   │   └────┤ SDA    VCC  ├──────┘
     │   │        │             │
     │   └────────┤ SCL    GND  ├──┐
     │            │             │  │
     │            │    LCD16x2  │  │
     │            │   I2C 0x27  │  │
     │            └─────────────┘  │
     │                             │
     │                             │
     │        ┌─────────────┐      │
     │   ┌────┤ SDA    VCC  ├──────┼──┘
     │   │    │             │      │
     │   │ ┌──┤ SCL    GND  ├──────┼──┐
     │   │ │  │             │      │  │
     │   │ │  │   QN8066    │      │  │
     │   │ │  │             │      │  │
     │   │ │  │ CEN   XCLK  ├──────┼──┼──── 32.768kHz
     │   │ │  │             │      │  │     Crystal
     │   │ │  │ ALI    RFO  ├──────┼──┼──── Antenna
     │   │ │  │             │      │  │
     │   │ │  │ ARI         │      │  │
     │   │ │  └─────────────┘      │  │
     │   │ │                       │  │
     │   │ └───────────────────────┘  │
     │   └───────────────────────────┼──┘
     │                               │
     │                               │
     │   ┌─────────────────────┐     │
     │   │    Rotary Encoder   │     │
     │   │                     │     │
     ├───┤ A                   │     │
     │   │                     │     │
     ├───┤ B                   │     │
     │   │                     │     │
     ├───┤ BTN                 │     │
     │   │                     │     │
     └───┤ GND                 │     │
         │                     │     │
         └─────────────────────┘     │
                                     │
     ┌───────────────────────────────┘
     │
     │   Common Ground
     └───────────────────────────────────

Hardware Components

Required Components:

1. Raspberry Pi Pico - Main microcontroller
2. QN8066 Module - FM transceiver
3. LCD 16x2 with I2C backpack - Display (address usually 0x27)
4. Rotary Encoder with push button - User interface
5. 32.768 kHz Active Crystal - Clock reference
6. Breadboard and jumper wires - Connections

Optional Components:

• Audio source - Connect to ALI/ARI pins
• Antenna or dummy load - Connect to RFO pin
• Pull-up resistors - 4.7kΩ for I2C (usually built into modules)

Pin Assignments

Raspberry Pi Pico	Component	Pin/Signal	Description
3.3V (Pin 36)	All modules	VCC	Power supply
GND (Pin 38)	All modules	GND	Common ground
GP0 (Pin 1)	I2C Bus	SDA	I2C Data
GP1 (Pin 2)	I2C Bus	SCL	I2C Clock
GP2 (Pin 4)	Encoder	A	Encoder channel A
GP3 (Pin 5)	Encoder	B	Encoder channel B
GP4 (Pin 6)	Encoder	Button	Push button
GP16 (Pin 21)	QN8066	CEN	Chip enable (optional)

Software Features

Display Information:

• Line 1: Current frequency (MHz) and stereo/mono indicator
• Line 2: Transmission power and current menu mode
• Menu indicator: Shows current selection mode (FRQ/PWR/MOD)

User Interface:

• Rotate encoder: Adjust current parameter
• Press button: Switch between modes (Frequency → Power → Mode → Frequency...)
• Serial monitor: Detailed status information

Operating Modes:

1. FRQ Mode: Adjust transmission frequency (87.5 - 108.0 MHz)
2. PWR Mode: Adjust transmission power (20 - 120)
3. MOD Mode: Toggle between Stereo and Mono

Libraries Required

Install these libraries through Arduino IDE Library Manager:

1. QN8066 - by PU2CLR
2. LiquidCrystal I2C - by Frank de Brabander

Usage Instructions

1. Upload the sketch to your Raspberry Pi Pico
2. Open Serial Monitor (115200 baud) for debugging
3. Use the encoder to navigate:
   • Turn to adjust current parameter
   • Press to switch between modes
4. Monitor the LCD for real-time information
5. Check serial output for detailed status

Troubleshooting

LCD Issues:

• Blank display: Check I2C address (try 0x3F instead of 0x27)
• Garbled text: Check I2C connections and power
• No backlight: Verify LCD I2C module power

Encoder Issues:

• No response: Check pin connections and pull-up resistors
• Erratic behavior: Add debouncing delay or hardware debouncing
• Button not working: Verify button pin and interrupt setup

QN8066 Issues:

• Device not detected: Check I2C connections and crystal
• No transmission: Verify frequency range and power settings
• Poor audio: Check audio input connections and levels

Advanced Features

This example can be extended with:

• RDS transmission - Add station name and text
• Frequency presets - Store favorite frequencies
• Audio level meters - Real-time audio monitoring
• Web interface - Use Pico W for remote control
• EEPROM storage - Save settings between power cycles

Serial Monitor Output Example

QN8066 Pico LCD Control Starting...
System ready!
Freq: 106.9 MHz | Power: 73 | Mode: Stereo | FSM: 10 | Audio: 45 mV
Freq: 107.5 MHz | Power: 73 | Mode: Stereo | FSM: 10 | Audio: 52 mV
Freq: 107.5 MHz | Power: 83 | Mode: Stereo | FSM: 10 | Audio: 52 mV

This example provides a complete, interactive FM transmitter control system with professional-grade user interface and monitoring capabilities.