How to Use Adafruit SPI Non-Volatile FRAM 8KB: Examples, Pinouts, and Specs

The Adafruit SPI Non-Volatile FRAM 8KB is a high-performance, ferroelectric random access memory (FRAM) module that provides robust, non-volatile data storage. Unlike traditional non-volatile memories like EEPROM or Flash, FRAM offers faster write speeds and a much higher endurance for write cycles. This makes it ideal for applications that require frequent or rapid data logging or updates, such as wear-leveling tasks, data caching, and real-time data collection. The module communicates with microcontrollers via the Serial Peripheral Interface (SPI) protocol.

• Data logging systems
• Real-time data collection
• Industrial control systems
• Gaming and entertainment devices
• Wearable electronics
• IoT devices requiring frequent updates

• Voltage: 3.3V to 5V logic and power
• Current: 0.3 mA (typical standby), 3 mA (maximum operating)
• Power Ratings: 15 mW (maximum operating power)
• Memory Size: 8 KBytes (64 Kbits)
• Write Endurance: 10^14 write cycles
• Data Retention: 10 years
• Operating Temperature Range: -40°C to +85°C

1. Powering the FRAM: Connect the Vcc pin to a 3.3V or 5V power supply, and the GND pin to the ground.

2. SPI Communication: Connect the CS, DI, DO, and SCK pins to the corresponding SPI pins on your microcontroller. For Arduino UNO, the connections are typically as follows:

   • CS to digital pin 10 (or any other digital pin if you change the pin number in your code)
   • DI (MOSI) to digital pin 11
   • DO (MISO) to digital pin 12
   • SCK to digital pin 13

3. Library Installation: Install the Adafruit FRAM SPI library via the Arduino Library Manager or download it from the Adafruit GitHub repository.

4. Initialization: In your code, initialize the FRAM module using the library's functions. Check for successful initialization before proceeding with read/write operations.

• Always ensure that the power supply voltage matches the FRAM module's specifications.
• Use pull-up resistors on the SPI lines if you encounter communication issues.
• Avoid exposing the FRAM to temperatures outside its operating range.
• Minimize the length of the SPI connections to reduce potential electromagnetic interference.

#include <Wire.h>
#include <Adafruit_FRAM_SPI.h>

// Pin definitions
#define CS_PIN 10

// Create an FRAM_SPI instance
Adafruit_FRAM_SPI fram = Adafruit_FRAM_SPI(CS_PIN);

void setup() {
  Serial.begin(9600);
  while (!Serial) {
    ; // Wait for serial port to connect
  }

  // Initialize SPI FRAM
  if (fram.begin()) {
    Serial.println("Found SPI FRAM");
  } else {
    Serial.println("No SPI FRAM found ... check your connections");
    while (1);
  }

  // Write example data to FRAM
  uint8_t testdata = 42;
  fram.writeEnable(true);
  fram.write8(0, testdata);
  fram.writeEnable(false);

  // Read back the data
  uint8_t result = fram.read8(0);
  Serial.print("Read: 0x"); Serial.println(result, HEX);
}

void loop() {
  // Nothing to do here
}

• FRAM not detected: Ensure that all SPI connections are secure and correct. Check that the correct CS pin is defined in your code.
• Incorrect data read/write: Verify that the write enable function is called before writing to the FRAM. Also, ensure that the power supply is stable and within the specified range.
• Communication errors: If you're experiencing sporadic communication, consider adding pull-up resistors to the SPI lines or shortening the connection wires.

• Double-check wiring against the pin configuration table.
• Use the example code provided to test basic functionality.
• Consult the Adafruit FRAM SPI library documentation for advanced functions and troubleshooting tips.

Q: Can I use this FRAM with a 5V microcontroller? A: Yes, the Adafruit SPI Non-Volatile FRAM 8KB is 5V tolerant on the SPI pins.

Q: How many write cycles can the FRAM handle? A: The FRAM can handle up to 10^14 write cycles, which is significantly higher than EEPROM or Flash.

Q: Do I need to perform any special operations before powering down the system? A: No, FRAM retains data without any special power-down sequence.

Q: Is it possible to use multiple FRAM modules on the same SPI bus? A: Yes, you can use multiple FRAM modules on the same SPI bus by assigning different CS pins for each module.