Embedis: I2C EEPROM Keystore

We needed a simple and efficient way to store configuration settings and values between projects, using common, low-cost, external I2C EEPROM memory.

The Embedis database is persistent, and can be used across multiple projects to configure your program settings for the specific hardware and network configuration that you are using. The Embedis database supports the internal CPU EEPROM storage by default, but you can also add other external memory devices easily, as we show with this example, by adding an external I2C EEPROM such as the 24AA64 (8K bytes) or the 24LC256 (32K bytes).

Now, you don't need to recompile your program and re-flash your device in order to change your device and project settings anymore. Project settings can be changed "on-the-fly" with just a serial or wireless interface! (some settings changes however, will require a restart/reboot to take effect.)

Installing Embedis

To Install Embedis in the Arduino IDE, please see the Detailed Install Directions. Embedis is installed using the Arduino Library Manager, from the top menu bar:

Sketch -> Include Library -> Manage Libraries -> Embedis

You will also need the ESP8266 tools and ESP8266 sketch data download utility installed with Arduino IDE 1.6.7 or later. For more information, please follow the board manager install directions at esp8266/Arduino.

Installing the extEEPROM Library

The extEEPROM library is installed using the Arduino Library Manager, from the top menu bar:

Sketch -> Include Library -> Manage Libraries -> extEEPROM

Loading the Example Project

After installing the Embedis library in the Arduino IDE, the Embedis examples will be available under the menu as:

File ->  Examples -> Embedis -> esp8266 -> Embedis_I2C_EEPROM

Make sure to select your specific ESP8266 board model under the Board Manager, and set the "port" to the correct COM: port for your board. Then just press the "Download" button to compile and download your project.

Using the Example Embedis_I2C_EEPROM Project

Once you have flashed your board using the Upload command, open the Arduino Serial Monitor and you can begin giving commands to Embedis. Type "commands" into the Arduino Serial Monitor, and get a list of commands:

Now this is where it gets really interesting, you have two (2) different memories available to you to store your data in, which in Embedis are referred to as "DICTIONARIES" and these are named EEPROM (internal to the CPU) and I2C_EEPROM (external chip on the I2C bus):

By using the Embedis "select" command, you can select which memory you are going to use to read and write, for example when you type "select EEPROM", then Embedis will return the number of bytes of free space in the EEPROM dictionary. The ESP8266 normally gives you 4096 bytes of "emulated" EEPROM, and two (2) of those bytes are used by Embedis for a pointer, so you have 4094 bytes to work with.

Similarly, when you "select I2C_EEPROM", Embedis will select the I2C_EEPROM and return the number of free bytes in that Embedis Keystore. If you are using a 24AA64, you will see that you have almost 8K bytes of storage to work with, and if using a 24AA256 you will have almost 32K of storage space! In the example below, we are using an 8K x 8 (24AA64) I2C EEPROM part:

Now you can start to add data to your Embedis Keystore using the "set" and "get" commands. Since the last "Dictionary" that was selected was the I2C_EEPROM, that is where our data will be written, for example:

So we created a key named "IPADDR" and set it to "192.168.1.127" . Make sure to use quotes around any string with spaces or special characters. Now let's use the "get IPADDR" command to retrieve the data from the Embedis Keystore.

There are many advanced features of Embedis, including the ability to publish and subscribe to changes in keys and the logging system. We'll cover those in upcoming projects here at the thingSoC platform!

You can use the Embedis keystore to hold all kinds of setup and configuration information, such as device pins, mode and baud rate settings, as well as sensor calibration data.

Happy Hacking!