1.13 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. TWI client expects two bytes of memory address from the TWI host and the memory address can range from 0x00 to 0x1FF. TWI client application supports following:

Byte Write: The 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 TWI host can write up-to 256 bytes (1 page). If more than 256 bytes are sent by the TWI host to the 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 TWI host sends NAK and generates a STOP condition.

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

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

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

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

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

1. Build and program FLEXCOM TWI EEPROM application from apps/flexcom/twi/master/flexcom_twi_eeprom/firmware onto the evaluation kit used as TWI host
2. Build and Program TWI client application onto the evaluation kit used as TWI client
3. Run application on TWI client board and then run the application on TWI host board

4. LED on the TWI host board indicates success or failure:

   • The LED is turned ON when the value read from the TWI client matches with the written value
   • The LED is turned OFF when the value read from the TWI client did not match with the written value