A RadioLib-based POCSAG transmitter implementation for the CC1101 radio module with configurable frequency offset capability.

Author: Anders Isaksson (SA7BNB)
Hardware Design: Anders Isaksson
Software Development: Anders Isaksson (based on RadioLib)

This project enables transmission of POCSAG (Post Office Code Standardisation Advisory Group) pager messages using a CC1101 radio transceiver module connected to a Wemos D1 Mini Pro. The implementation includes a frequency offset feature for precise frequency calibration.

• Wemos D1 Mini Pro (or compatible ESP8266 board)
• CC1101 transceiver module
• LED (optional, for transmission indicator)

LED: Connect to GPIO 5 (optional)

• Interactive Serial Interface: Send messages via serial monitor with real-time input
• Flexible Message Format: Support for both default and custom RIC (Radio Identity Code) addressing
• Frequency Offset Calibration: Adjustable frequency offset for precise tuning
• Maximum Power Output: Configured for +10 dBm output power
• Visual Feedback: LED indicator for successful transmissions
• Input Validation: Built-in checks for RIC and message validity

• Arduino IDE or PlatformIO
• RadioLib library

1. Install the RadioLib library in your Arduino IDE:

   • Go to Sketch → Include Library → Manage Libraries
   • Search for "RadioLib"
   • Install the latest version

2. Clone or download this repository

3. Open the .ino file in Arduino IDE

4. Configure your board settings:

   • Board: "LOLIN(WEMOS) D1 mini Pro"
   • Upload Speed: 921600
   • CPU Frequency: 80 MHz

5. Upload to your Wemos D1 Mini Pro

Adjust these parameters at the top of the code:

float BASE_FREQUENCY = 433.92;      // Nominal frequency (MHz)
float FREQUENCY_OFFSET = 0.015;     // Offset in MHz (15 kHz)

• BASE_FREQUENCY: The nominal operating frequency
• FREQUENCY_OFFSET: Fine-tuning offset in MHz
  • Positive values increase frequency
  • Negative values decrease frequency

The transmitter is configured for maximum power (+10 dBm, approximately 10 mW). Modify the power setting in the code if needed:

radio.setOutputPower(10);  // Range: -30 to +10 dBm

The transmitter supports two input formats:

1. With custom RIC: RIC::Message

   • Example: 123456::Hello World
   • RIC must be between 1 and 2,097,151

2. Without RIC: Message

   • Example: Test message
   • Uses default RIC 123456

1. Open the Serial Monitor (115200 baud)
2. Wait for the prompt: Enter command:
3. Type your message in one of the supported formats
4. Press Enter to transmit
5. Watch for transmission confirmation

• Maximum message length: 40 characters
• Longer messages are automatically truncated
• Only ASCII characters are supported

RadioLib POCSAG Transmitter Starting...
Base frequency: 433.92000 MHz
Frequency offset: 0.01500 MHz
Actual transmit frequency: 433.93500 MHz
[CC1101] Initializing ... success!
[Pager] Initializing ... success!
[CC1101] Setting maximum power ... MAX POWER SET!

=== POCSAG Message Sender ===
Format: RIC::Message (e.g., '123456::Hello World')
Or just: Message (uses default RIC 123456)
TX Frequency: 433.93500 MHz
Enter command: 123456::Test message
Sending: 'Test message' to RIC 123456
[Pager] Transmitting ... SUCCESS!
Message sent successfully!

• Protocol: POCSAG
• Baud Rate: 1200 bps
• Modulation: FSK (Frequency Shift Keying)
• Encoding: ASCII
• Default Frequency: 433.92 MHz (adjustable)
• RIC Range: 1 to 2,097,151 (21-bit addressing)

⚠️ Important:

• Ensure you have the appropriate license to transmit on your chosen frequency
• Respect local regulations regarding radio transmissions
• Be aware of frequency allocations in your country
• This project is intended for educational and amateur radio use only
• The author assumes no liability for misuse or regulatory violations

• Check wiring connections
• Verify power supply (3.3V for CC1101)
• Confirm antenna is connected
• Check serial monitor for error codes

• Use an SDR or spectrum analyzer to verify actual transmission frequency
• Adjust FREQUENCY_OFFSET in small increments (0.001 MHz)
• Temperature can affect frequency stability

• Verify RIC matches receiver configuration
• Confirm receiver is tuned to the correct frequency
• Check transmission power and antenna placement

This project is provided as-is for educational purposes. Please check RadioLib's license for library-specific terms.

• Hardware design and software implementation by Anders Isaksson (SA7BNB)
• Built using the excellent RadioLib by Jan Gromeš
• POCSAG protocol implementation by RadioLib contributors

• POCSAG Protocol Information
• CC1101 Datasheet
• RadioLib Documentation
• https://github.com/sa7bnb/Wemos-Mini-Pro-Pocsag-Transmitter-v1.0