MB85RC256V-FRAM-RK (community library)
|All Versions||0.0.5, 0.0.4, 0.0.2, 0.0.1|
Particle driver for DS75 temperature sensor
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Library Read Me
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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:
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.
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:
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.
- Fix compile error for ambiguous receiveFrom() with 1.5.0.rc.2.
- Added moveData() method to efficiently move data. Supports overlap.
- 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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