ST STM32F2 User Manual

Overview of HAL drivers
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2.12.3 HAL IO operation process
The HAL functions with internal data processing like transmit, receive, write and read are
generally provided with three data processing modes as follows:
Polling mode
Interrupt mode
DMA mode
2.12.3.1 Polling mode
In Polling mode, the HAL functions return the process status when the data processing in
blocking mode is complete. The operation is considered complete when the function
returns the HAL_OK status, otherwise an error status is returned. The user can get more
information through the HAL_PPP_GetState() function. The data processing is handled
internally in a loop. A timeout (expressed in ms) is used to prevent process hanging.
The example below shows the typical Polling mode processing sequence :
HAL_StatusTypeDef HAL_PPP_Transmit ( PPP_HandleTypeDef * phandle, uint8_t
pData,
int16_tSize,uint32_tTimeout)
{
if((pData == NULL ) || (Size == 0))
{
return HAL_ERROR;
}
(…) while (data processing is running)
{
if( timeout reached )
{
return HAL_TIMEOUT;
}
}
(…)
return HELIAC; }
2.12.3.2 Interrupt mode
In Interrupt mode, the HAL function returns the process status after starting the data
processing and enabling the appropriate interruption. The end of the operation is indicated
by a callback declared as a weak function. It can be customized by the user to be informed
in real-time about the process completion. The user can also get the process status
through the HAL_PPP_GetState() function.
In Interrupt mode, four functions are declared in the driver:
HAL_PPP_Process_IT(): launch the process
HAL_PPP_IRQHandler(): the global PPP peripheral interruption
__weak HAL_PPP_ProcessCpltCallback (): the callback relative to the process
completion.
__weak HAL_PPP_ProcessErrorCallback(): the callback relative to the process Error.
To use a process in Interrupt mode, HAL_PPP_Process_IT() is called in the user file and
HAL_PPP_IRQHandler in stm32f2xx_it.c.
The HAL_PPP_ProcessCpltCallback() function is declared as weak function in the driver.
This means that the user can declare it again in the application. The function in the driver is
not modified.

ST STM32F2 Specifications

General

Brand	ST
Model	STM32F2
Category	Microcontrollers
Language	English