It's easy to use the I2C FRAM Breakout with CircuitPython and the Adafruit CircuitPython FRAM library.
CircuitPython Microcontroller Wiring
First we'll wire up the I2C FRAM Breakout to a microcontroller, as was shown in the Arduino Test page.
Here is an example of wiring the breakout to a Feather M0 Basic:
If you'd like to use the hardware write protection, connect another GPIO to the sensor's WP pad, like so:
- Board 3V to sensor VIN
- Board GND to sensor GND
- Board SDA to sensor SDA
- Board SCL to sensor SCL
- Board D5 to sensor WP
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:
import board import digitalio import adafruit_fram i2c = board.I2C() fram = adafruit_fram.FRAM_I2C(i2c)
Or, if you're using the hardware write protection:
import board import digitalio import adafruit_fram i2c = board.I2C() wp = digitalio.DigitalInOut(board.D6) fram = adafruit_fram.FRAM_I2C(i2c, wp_pin=wp)
Now you can write or read to any address locations:
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:
# SPDX-FileCopyrightText: 2021 ladyada for Adafruit Industries
# SPDX-License-Identifier: MIT
## Simple Example For CircuitPython/Python I2C FRAM Library
import board
import busio
import adafruit_fram
## Create a FRAM object (default address used).
i2c = busio.I2C(board.SCL, board.SDA)
fram = adafruit_fram.FRAM_I2C(i2c)
## Optional FRAM object with a different I2C address, as well
## as a pin to control the hardware write protection ('WP'
## pin on breakout). 'write_protected()' can be used
## independent of the hardware pin.
# import digitalio
# wp = digitalio.DigitalInOut(board.D10)
# fram = adafruit_fram.FRAM_I2C(i2c,
# address=0x53,
# wp_pin=wp)
## Write a single-byte value to register address '0'
fram[0] = 1
## Read that byte to ensure a proper write.
## Note: reads return a bytearray
print(fram[0])
## Or write a sequential value, then read the values back.
## Note: reads return a bytearray. Reads also allocate
## a buffer the size of slice, which may cause
## problems on memory-constrained platforms.
# values = list(range(100)) # or bytearray or tuple
# fram[0:100] = values
# print(fram[0:100])
