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A71CH on stm32, keep getting "Unexpected Sequence" error

Question asked by Dogus Ural on Mar 11, 2019
Latest reply on Mar 19, 2019 by Estephania Martinez

Hello, I have been trying to interface A71CH with my STM board B-L475E-IOT01a over i2C for the last two weeks without success. I am stuck on some parts and I could your guidance on the topics below.


  • Altough my i2c signals match the ones in your datasheet (AN12207) .I am getting 167 to my status queries and device is stuck in this mode until i perform a cold reset. After the reset device returns 7 as a response to my status command for once which is the expected behavior then goes back to sending 167 and stuck there.Below you can see my Status message with repeated start condition in accordance with your "read byte" messages.Error code 167 means unexpected sequence error according to the datasheet but everything seems to be right.

  • Is there a guide about how to use the IC without your source files ? For example I want to init the module but all I can find is your smComSI2C_Open() function. To init the A71CH , I am calling
    sci2c_GetStatus -> sci2c_Wakeup() -> sci2c_ReadAnswerToReset() ->sci2c_ParameterExchange
    respectiverly. Is there a document on this sequence .
smComSCI2C_Open(ESTABLISH_SCI2C, 0x00, Atr, &AtrLen)