[FAQ] AM263P4: I2C OWN TArget Address

Hi

This FAQ clarifies the different I2C addresses used in the AM261x MCU+ SDK, which is a common source of confusion for developers. There are two types of addresses you will come across when working with I2C in MCU_PLUS_SDK. 

- Own Target Address (As highlighted in the image above)

- Target address

AM26x I2C can operate in two modes, Controller and Peripheral (Transmitter). The addressing depends on what mode the I2C is operating in.\

Controller mode:

AM26x I2C starts the I2C transaction, for e.g. AM261x talks to EEPROMs, LED Arrays etc. This is where the remote device's address is used.

Peripheral mode:

AM26x I2C waits for another Controller to initiate a transaction (for e.g. another MCU starts the transaction). This is when Own target address is used.

In summary,

YOUR AM26x's address -> Use "Own Target Address" in SysConfig
REMOTE device's address -> Use "Target Address" field in i2cTransaction.targetAddress in application code.

To dive deeper, 

Own Target Address

• What it is: The I2C address that YOUR AM26x will respond to when in peripheral mode.
• When to use:
  When AM26x is in peripheral/target mode. When another controller needs to talk to YOUR AM26x. 
  
  
• Where to set:
  In SysConfig as shown in the image below:
  
• COMMON MISTAKE:
  • WRONG: "I want to talk to EEPROM at 0x51, so I set ownTargetAddr to 0x51"
  • RIGHT: You should set targetAddress to 0x51 in controller mode! ownTargetAddr is only for when YOUR AM26x is the peripheral.

Target Address

• What it is:The I2C address of the REMOTE device you want to communicate with.
• When to use: When AM26x is in controller mode. When YOU initiate communication with an I2C device. For sensors, EEPROMs, LED drivers, temperature sensors, etc.
• Where to set:
  In application code, in the I2C_Transaction structure
  

  I2C_Transaction i2cTransaction;
  I2C_Transaction_init(&i2cTransaction);
  
  i2cTransaction.targetAddress = 0x4C; // for e.g.Temperature sensor address
  i2cTransaction.readBuf = rxBuffer;
  i2cTransaction.readCount = 2;
  
  I2C_transfer(i2cHandle, &i2cTransaction);

  
  
  How to find target address:
  1. Check the I2C device datasheet
  2. Check your board schematic for address pin settings
  
  
• COMMON MISTAKE:
  • WRONG: Setting ownTargetAddr to talk to a device
  • RIGHT: Set targetAddress in your I2C_Transaction in controller mode

Regards,
Shaunak