How to Use Adafruit FONA - Mini Cellular GSM uFL Breakout: Examples, Pinouts, and Specs

The Adafruit FONA is a compact cellular GSM breakout board designed to bring wireless network connectivity to your projects. It supports GSM/GPRS on 850/900/1800/1900MHz bands, enabling voice calls, SMS messages, and data connections in a tiny package. This breakout is perfect for IoT devices, remote sensors, wearables, and any application where cellular communication is needed.

• Remote monitoring and control systems
• IoT devices requiring 2G/3G connectivity
• Wearable devices with cellular capabilities
• SMS alert systems
• Voice communication systems

• Network Support: Quad-band 850/900/1800/1900MHz
• Data Support: GPRS multi-slot class 12/10, GPRS mobile station class B
• Connectivity: 2G GSM/GPRS
• Voltage Requirements: 3.4-4.4VDC
• Current Consumption: 250mA average during transmission
• Antenna Connector: uFL
• Interfaces: UART, I2C, SPI, GPIO, ADC, PWM

1. Power Supply: Connect a stable power source to the Vio and GND pins. Ensure the voltage is within the specified range.
2. Antenna: Attach a GSM antenna to the uFL connector for network communication.
3. UART Communication: Connect the RX and TX pins to your microcontroller's UART interface for serial communication.
4. Power On/Off: The Key pin can be used to turn the module on or off by applying a low signal for a short duration.
5. Network Status: Monitor the NS pin for network status indication.

• Ensure the power supply is clean and within the specified voltage range to avoid damaging the module.
• Use a level shifter if your microcontroller operates at a different logic level than the FONA's 3.3V-5V range.
• Place the antenna in a position with minimal obstructions to ensure good signal reception.
• Always disconnect the power before making or changing connections to prevent accidental shorts or damage.

• No Network Connection: Ensure the antenna is properly connected and the SIM card is activated and inserted correctly.
• Module Not Powering On: Check the power supply and connections to the Key and RST pins.
• Serial Communication Failure: Verify the UART connections and baud rate settings.

• Power Issues: Use a multimeter to check the voltage at the Vio pin.
• Signal Strength: Use the AT command AT+CSQ to check signal quality.
• SIM Card: Ensure the SIM card is not PIN-locked and is compatible with the GSM bands supported by the module.

• Q: Can I use the Adafruit FONA with an Arduino UNO? A: Yes, you can connect the FONA to an Arduino UNO using the UART interface.

• Q: What is the default baud rate for the FONA? A: The default baud rate is 9600 bps.

• Q: How do I send an SMS using the FONA? A: You can send an SMS using the AT command AT+CMGS.

#include <SoftwareSerial.h>

// Define the serial connection to the FONA
SoftwareSerial fonaSerial(2, 3); // RX, TX
int FONA_PWR = 4; // FONA Key pin connected to digital pin 4

void setup() {
  pinMode(FONA_PWR, OUTPUT);
  digitalWrite(FONA_PWR, LOW);
  delay(1000); // Hold the key low for 1 second
  digitalWrite(FONA_PWR, HIGH);

  // Start serial communication with FONA
  fonaSerial.begin(9600);
  Serial.begin(9600); // Start serial communication with PC
}

void loop() {
  // Check if data has been received from the FONA
  if (fonaSerial.available()) {
    Serial.write(fonaSerial.read());
  }

  // Check if data has been received from the PC's serial monitor
  if (Serial.available()) {
    fonaSerial.write(Serial.read());
  }
}

This example demonstrates how to establish a basic serial communication between an Arduino UNO and the Adafruit FONA. The SoftwareSerial library is used to create a secondary serial connection on digital pins 2 and 3, while the FONA's Key pin is toggled to power on the module. Data received from the FONA is sent to the PC's serial monitor, and vice versa.