Resolved! HAL_I2C_Master_Transmit works, HAL_I2C_Master_Transmit_IT does not.
I’m trying to replace a blocking call to HAL_I2C_Master_Transmit() with the interrupt version HAL_I2C_Master_Transmit_IT(). The blocking HAL_I2C_Master_Transmit() call works perfectly. The HAL_I2C_Master_Transmit_IT() call sends completely different ...