1.10 FLEXCOM TWI EEPROM Emulation

This example uses the FLEXCOM TWI peripheral library in client mode and emulates an EEPROM of 512 bytes. There are two pages each of size 256 bytes. FLEXCOM TWI client expects two bytes of memory address from the FLEXCOM TWI host and the memory address can range from 0x00 to 0x1FF. FLEXCOM TWI client application supports following:

Byte Write: The FLEXCOM TWI host sends the client address, followed by two bytes of memory address. The client provides the data present at the requested memory address.

Page Write: A page write is initiated the same way as a byte write, but the FLEXCOM TWI host can write up-to 256 bytes (1 page). If more than 256 bytes are sent by the FLEXCOM TWI host to the FLEXCOM TWI client, the memory address will “roll over” and previous data will be overwritten. The address “roll over” during write is from the last byte of the current page to the first byte of the same page.

Current Address Read: The internal memory address counter maintains the last address accessed during the last read or write operation, incremented by one. Once the device address with the read/write bit set to one is clocked in and acknowledged by the EEPROM, the data byte at the current address is serially clocked out. After reading the data from the current address, the FLEXCOM TWI host sends NAK and generates a STOP condition.

Random Read: The FLEXCOM TWI host writes the 2 byte memory address and then reads the data from that memory address. After reading the data, the FLEXCOM TWI host sends NAK and generates a STOP condition.

Sequential Read: Sequential reads are initiated by either a current address read or a random address read. As long as the EEPROM receives an acknowledge, it will continue to increment the memory address and serially clock out sequential data bytes. When the memory address limit is reached (0x1FF), the memory address will “roll over” to 0x00 and the sequential read will continue. The sequential read operation is terminated when the FLEXCOM TWI host sends a NAK and generates a STOP condition.

To run the application, two evaluation kits will be required - one acting as the FLEXCOM TWI host and the other as the FLEXCOM TWI client. The FLEXCOM TWI host application to be used for this demo application is available under apps/flexcom/twi/master/flexcom_twi_eeprom/firmware folder. FLEXCOM TWI host writes an array of values to the FLEXCOM TWI client and verifies the value written by reading the values back and comparing it to the value written.

To clone or download this application from Github, go to the main page of this repository and then click Clone button to clone this repository or download as zip file. This content can also be downloaded using content manager by following these instructions.

Path of the application within the repository is apps/flexcom/twi/slave/i2c_eeprom_emulation/firmware.

To build the application, refer to the following table and open the project using its IDE.

To load the application binary onto the target device, we need to use at91bootstrap loader. Refer to the at91bootstrap loader documentation for details on how to configure, build and run bootstrap loader project and use it to bootstrap the application binaries.

The following table shows the target hardware for the application projects.

Hardware setup requires two boards, one acting as the FLEXCOM TWI Host and the other as the FLEXCOM TWI client.

1. Build FLEXCOM TWI EEPROM application from apps/flexcom/twi/master/flexcom_twi_eeprom/firmware (used as FLEXCOM TWI host) using its IDE
2. Build FLEXCOM TWI client application (used as FLEXCOM TWI client) using its IDE
3. Run application on FLEXCOM TWI client board and then run the application on FLEXCOM TWI host board
4. LED on the FLEXCOM TWI host board indicates success or failure:
   • The LED is turned ON when the value read from the FLEXCOM TWI client matches with the written value
   • The LED is turned OFF when the value read from the FLEXCOM TWI client did not match with the written value