Distributors: Atmel Corp
ABOUT:
- External EEPROM is used to store data, much like storing information on you harddrive. The information won't be lost during once the power is turned off and will only be lost if give specific instructions to erase the data.
- The Atmega microcontroller series (the microcontroller used on the Arduino board), contains internal EEPROM, but it is very small. (on the Atmega8, the EEPROM can hold 512 bytes only). This is the reason we're adding external EEPROM for our project.
- We will use the external EEPROM to store the collected pollution and GPS information, and will later download this data to our PC's.
COMMUNICATING WITH THE EEPROM:
- In order to communicate with the external EEPROM, we will be using the Serial Peripheral Interface (SPI) protocol. This is a very common protocol used to communicate between the Atmega (and other) microcontroller with external devices. The Atmega 8 microcontroller contains a special register (SPI Control Register (SPCR)), to allow for this type of communication.
- With an SPI connection there is always one master device (usually a microcontroller) which controls the peripheral devices.
Typically there are four lines common to all the devices:
- Master In Slave Out (MISO) - The Slave line for sending data to the master,
- Master Out Slave In (MOSI) - The Master line for sending data to the peripherals,
- Serial Clock (SCK) - The clock pulses which synchronize data transmission generated by the master, and
- Slave Select pin - allocated on each device which the master can use to enable and disable specific devices and avoid false transmissions due to line noise.
- During our final kit assembly we will learn how to interface the external EEPROM with the Arduino and use the SPI protocol.
- Also see the full interfacing tutorial provided on the Arduino Website: EEPROM Tuturial .