Problems with I2C: HAL_I2C_ERROR_AF

[Luis Ber]

Hello,

I'm using the STM32L451VC microcontroller to perform a communication through I2C protocol to a programmable resistor (AD5272). It is working well when I do a NRST to the microcontroller, but when I start the program from the batteries (without reset) I get the HAL_I2C_ERROR_AF error from the I2C HALs.

Anybody can explain me why is it happening? Which possible reasons can produce this error? And only when the program starts from power up (if i do a NRST all works properly).

Thank you very much!