Adafruit SPI FRAM Breakouts

by lady ada and

published May 23, 2014, last edited January 22, 2025
last major update December 02, 2022

posted in Components Adafruit Products Breakout Boards/ Storage

Beginner

Product guide

CircuitPython

You can use the same wiring and test code for our older non-level-shifted breakout, or our newer versions which have a regulator and level shifting circuitry!

It's easy to use the SPI FRAM Breakout with Python or CircuitPython and the Adafruit CircuitPython FRAM module. This module allows you to easily write Python code that reads the humidity, temperature, pressure, and more from the sensor.

CircuitPython Microcontroller Wiring

First we'll wire up a SPI FRAM Breakout to a microcontroller.

Here is an example of wiring the breakout to a Feather M0 Basic or a Feather M4:

Board 3V to sensor VIN
Board GND to sensor GND
Board SCK to sensor SCK
Board MOSI to sensor MOSI
Board MISO to sensor MISO
Board D5 to sensor CS

If you'd like to use the hardware write protection, connect another GPIO to the sensor's WP pad, like so:

components_SPI_FRAM_original_FeatherM0_write_protect.png

Board 3V to sensor VIN
Board GND to sensor GND
Board SCK to sensor SCK
Board MOSI to sensor MOSI
Board MISO to sensor MISO
Board D5 to sensor CS
Board D6 to sensor WP

The CircuitPython library takes advantage of the software level write protection on the SPI FRAM chip, so using the hardware write protection isn't necessary. However, the hardware write protection could be useful with an external source of control, like a separate microcontroller.

CircuitPython Installation of FRAM Library

You'll need to install the Adafruit CircuitPython FRAM library on your CircuitPython board.

First make sure you are running the latest version of Adafruit CircuitPython for your board.

Next you'll need to install the necessary libraries to use the hardware--carefully follow the steps to find and install these libraries from Adafruit's CircuitPython library bundle. Our CircuitPython starter guide has a great page on how to install the library bundle.

For non-express boards like the Trinket M0 or Gemma M0, you'll need to manually install the necessary libraries from the bundle:

adafruit_fram.mpy
adafruit_bus_device

Before continuing make sure your board's lib folder or root filesystem has the adafruit_fram.mpy, and adafruit_bus_device files and folders copied over.

Next connect to the board's serial REPL so you are at the CircuitPython >>> prompt.

CircuitPython Usage

To demonstrate the usage of the breakout we'll initialize it, write data to the FRAM, and read that data from the board's Python REPL.

Run the following code to import the necessary modules and initialize the SPI connection with the breakout:

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import board
import busio
import digitalio
import adafruit_fram
spi = busio.SPI(board.SCK, board.MOSI, board.MISO)
cs = digitalio.DigitalInOut(board.D5)
fram = adafruit_fram.FRAM_SPI(spi, cs)

import board
import busio
import digitalio
import adafruit_fram
spi = busio.SPI(board.SCK, board.MOSI, board.MISO)
cs = digitalio.DigitalInOut(board.D5)
fram = adafruit_fram.FRAM_SPI(spi, cs)

Or, if you're using the hardware write protection:

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import board
import busio
import digitalio
import adafruit_fram
spi = busio.SPI(board.SCK, board.MOSI, board.MISO)
cs = digitalio.DigitalInOut(board.D5)
wp = digitalio.DigitalInOut(board.D6)
fram = adafruit_fram.FRAM_SPI(spi, cs, wp_pin=wp)

import board
import busio
import digitalio
import adafruit_fram
spi = busio.SPI(board.SCK, board.MOSI, board.MISO)
cs = digitalio.DigitalInOut(board.D5)
wp = digitalio.DigitalInOut(board.D6)
fram = adafruit_fram.FRAM_SPI(spi, cs, wp_pin=wp)

The default address space is 8 KByte for the smallest FRAM device. If you are using a larger FRAM device like the 4Mbit / 512 KByte use max_size during constructor initialization.

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fram = adafruit_fram.FRAM_SPI(spi, cs, max_size = 524288)

fram = adafruit_fram.FRAM_SPI(spi, cs, max_size = 524288)

Now you can write or read to any address locations:

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fram[0] = 1

fram[0]

fram[0] = 1

fram[0]

Reading the FRAM returns a bytearray. To get a "raw" value, use the index of the value's location. Some various ways to get values are as such:

Full Example Code

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# SPDX-FileCopyrightText: 2021 ladyada for Adafruit Industries
# SPDX-License-Identifier: MIT

## Simple Example For CircuitPython/Python SPI FRAM Library

import board
import busio
import digitalio
import adafruit_fram

## Create a FRAM object.
spi = busio.SPI(board.SCK, board.MOSI, board.MISO)
cs = digitalio.DigitalInOut(board.D5)
fram = adafruit_fram.FRAM_SPI(spi, cs)

## Write a single-byte value to register address '0'

fram[0] = 1

## Read that byte to ensure a proper write.
## Note: 'read()' returns a bytearray

print(fram[0])

## Or write a sequential value, then read the values back.
## Note: 'read()' returns a bytearray. It also allocates
##       a buffer the size of 'length', which may cause
##       problems on memory-constrained platforms.

# values = list(range(100))  # or bytearray or tuple
# fram[0:100] = values
# print(fram[0:100])

# SPDX-FileCopyrightText: 2021 ladyada for Adafruit Industries
# SPDX-License-Identifier: MIT

## Simple Example For CircuitPython/Python SPI FRAM Library

import board
import busio
import digitalio
import adafruit_fram

## Create a FRAM object.
spi = busio.SPI(board.SCK, board.MOSI, board.MISO)
cs = digitalio.DigitalInOut(board.D5)
fram = adafruit_fram.FRAM_SPI(spi, cs)

## Write a single-byte value to register address '0'

fram[0] = 1

## Read that byte to ensure a proper write.
## Note: 'read()' returns a bytearray

print(fram[0])

## Or write a sequential value, then read the values back.
## Note: 'read()' returns a bytearray. It also allocates
##       a buffer the size of 'length', which may cause
##       problems on memory-constrained platforms.

# values = list(range(100))  # or bytearray or tuple
# fram[0:100] = values
# print(fram[0:100])

Page last edited January 22, 2025