MB85RC256V-FRAM-RK (community library)

Summary

Particle driver for DS75 temperature sensor

Example Build Testing

Library Read Me

This content is provided by the library maintainer and has not been validated or approved.

MB85RC256V-FRAM-RK

Particle driver for MB85RC FRAMs (64, 256, 512, and 1M)

This little board is a FRAM (Ferroelectric RAM). I got mine from Adafruit.

It's 32 Kbytes in size, and the main benefit is that it's non-volatile like EEPROM so the contents are preserved if you remove power, but it's also very fast and doesn't have the limited wear cycles of EEPROM.

There are also a bunch of other variations in different sizes for just the chip part:

Circuit

The pins on the Adafruit breakout connect as typical for an I2C device:

• VCC to 3V3 (can also use VIN for a 5V I2C bus)
• GND to GND
• WP not connected (connect to VCC to prevent writes to the memory)
• SCL connect to D1 (SCL) (blue in the picture)
• SDA connect to D0 (SDA) (green in the picture)
• A2 not connected. Connect to VCC to change the I2C address.
• A1 not connected. Connect to VCC to change the I2C address.
• A0 not connected. Connect to VCC to change the I2C address.

Circuit (image removed)

The Adafruit board has built-in pull-ups on SDA and SCL so you don't need to add them. You will need pull-ups with a bare chip.

It also has pull-downs on A2, A1, and A0, so you can leave them unconnected.

Using the code

Typically you create a global variable for the FRAM:

MB85RC256V fram(Wire, 0);

The first parameter is the Wire interface to use, typically Wire (D0/D1). On the Electron you can also use Wire1 (C4/C5).

The second parameter is the address. Pass 0 if you left the A0-A3 pins unconnected. It can be 0-7 depending on the value set on A0-A3.

From setup you typically call:

fram.begin();

To read and write data you use the readData and writeData methods:

bool readData(size_t framAddr, uint8_t *data, size_t dataLen);
bool writeData(size_t framAddr, const uint8_t *data, size_t dataLen);

You can also use get and put like the EEPROM API. This makes it easy to convert code between using the built-in EEPROM and FRAM as you can use the calls nearly identically.

This also works with other chips:

MB85RC64 fram(Wire, 0);
MB85RC512 fram(Wire, 0);
MB85RC1M fram(Wire, 0);

Note that with the MB85RC1M chip, the A0 pin is N/C. You can leave it unconnected, or connect it to VCC or GND. Because of this, the only acceptable address values for the MB85RC1M are 0, 2, 4, and 6.

Version History

0.0.5 (2020-03-10)

• Fix compile error for ambiguous receiveFrom() with 1.5.0.rc.2.

0.0.4 (2019-11-18)

• Added moveData() method to efficiently move data. Supports overlap.

0.0.3 (2019-11-18)

• Added support for MB85RC64, MB85RC512, MB85RC1M
• Now surrounds transactions with WITH_LOCK(wire) for thread safety
• Minimum support Device OS version is now 1.0.0

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