Question
X-CUBE-SMBUS 2.1.0 - Optimized builds hang when waiting on STACK_SMBUS_IsReady()
In the code examples provided with AN4502, this pattern is used often:
while ( STACK_SMBUS_IsReady(pcontext) != SMBUS_SMS_READY) { }
But in our code, when built with the Release CMake preset, this hangs forever.
My understanding is that this is because the `StateMachine` member of the SMBus context struct (SMBUS_StackHandleTypeDef) is getting updated by the SMBUS interrupt handlers, but it isn't marked volatile:
* @brief Stack state machine handling structure - the stack operation context
*/
typedef struct
{
uint32_t StateMachine; /*!< Keeps track of current stack state */
SMBUS_HandleTypeDef *Device; /*!< HAL driver handle */
uint8_t *ARP_UDID; /*!< A UDID used in ARP */
st_command_t *CurrentCommand; /*!< NULL, unless a command is being processed */
st_command_t *CMD_table; /*!< Pointer to first record in the table of all supported commands */
uint32_t CMD_tableSize; /*!< The supported commands table size */
#ifdef PMBUS13
SMBUS_ZoneStateTypeDef TheZone; /*!< The zone structure */
#endif
uint16_t Byte_count; /*!< Indicates current buffer position */
uint16_t SlaveAddress; /*!< Master remembers to which slave it is talking to */
uint8_t OwnAddress; /*!< Device address, ARA response / Host: Address of the device that sent alert / */
uint8_t OpMode; /*!< Operation mode (read/write) */
uint8_t SRByte; /*!< A preset byte for use in Send byte/ Receive byte transactions */
uint8_t Buffer[STACK_NBYTE_SIZE+2U]; /*!< The I/O buffer on which the SMBUS stack operates
extra 2 bytes are command code and block length */
}
SMBUS_StackHandleTypeDef;
I worked around the issue by declaring our own pointer to the SMBus context, but this isn't optimal, as it marks the entire struct volatile, and causes a ton of compiler warnings to be thrown:
extern volatile SMBUS_StackHandleTypeDef *pcontext;