Multiple I2C slaves on one bus / adl_busSubscribe()


There are two I2C slaves attached to the same I2C bus on a Q2686RD based design.

From within my OpenAT application, I am using adl_busSubscribe(ADL_BUS_ID_I2C, 1, …) to obtain a handle to communicate with them.

As long as I am only issuing one adl_busSubscribe() for one of the two slave addresses, I can use adl_busRead() and adl_busWrite() to communicate with the slaves.

However, if I use adl_busSubscribe() twice, one for each of the I2C slave adresses, the second one fails, and subsequent adl_busRead/Write only work for the I2C slave that I specified in the first adl_busSubscribe().

Given that I2C is a bus and many slaves on one bus are frequent, this seems strange to me. There is no hardware/electrical limitation in talking to multiple slaves, so there shouldn’t be any limitations in OpenAT / ADL either. Did anyone succeed talking to multiple slaves from and OpenAT application? Any help is appreciated.

My environment is Q2686RD with Firmware and OpenAT OS




You have to unsubscribe after communication. Documentation is not that detailed about it.

sI2c_Config.ChipAddress = u8Adr >> 1;
  s32Handle = adl_busSubscribe(ADL_BUS_ID_I2C, 1, &sI2c_Config);

  s32Result = OK;
    s32Result = adl_busWrite(s32Handle, &sAccessCfg, u8TxLen, pu8Data);
  if((s32Result >= OK) && u8RxLen)
    s32Result = adl_busRead(s32Handle, &sAccessCfg, u8RxLen, pu8Data);


best regards,
Gregor Bader


Really :question: :exclamation: :open_mouth:

What a truly bizarre idea :exclamation: :open_mouth:

As laf0rge says, the whole point of a bus is exactly that it should support multiple devices :exclamation:


:laughing: We both know ADL for a long time.