Use case: USART RX in DMA mode

Sequence diagram

USART receive in DMA mode

@startuml participant "User Application" as p1 participant "HAL USART driver" as p2 participant "DMA" as p3 participant "DMAx_IRQHandler" as p4 == USART HAL Receive DMA == p1->p2: <color: green> HAL_USART_Receive_DMA(&husart, aRxBuffer, DATA_TO_RECEIVE_SIZE) note over p2 #00FF00 Receiving data ongoing end note p2->p3: HAL_DMA_Start_IT() p3-->p2: HAL_OK p2-->p1: HAL_OK p4<-: DMAx complete interrupt p4->p3: HAL_DMA_IRQHandler note over p3 #00FF00 End of receiving data end note p3->p2: XferCpltCallback p2->p1: HAL_USART_RxCpltCallback(&husart->rx_xfer_count) @enduml

Code snippet

HAL1

HAL2 

#define DATA_TO_RECEIVE_SIZE  255

uint8_t aRxBuffer[DATA_TO_RECEIVE_SIZE];

USART_HandleTypeDef husart;

/* Ensure that all required peripherals
(USART, GPIO, DMA, NVIC,etc.) are configured properly
/*
...
*/

/* USART register Receive complete user callback */
HAL_USART_RegisterCallback(&husart, HAL_USART_RX_CB_ID,
                              USART_RxCpltCallback);

/* Start a USART Process in DMA mode */
HAL_USART_Receive_DMA(&husart, aRxBuffer,
                        DATA_TO_RECEIVE_SIZE)

#define DATA_TO_RECEIVE_SIZE  255

uint8_t aRxBuffer[DATA_TO_RECEIVE_SIZE];

hal_usart_handle_t husart;

/* Ensure that all required peripherals
(USART, GPIO, DMA, NVIC,etc.) are configured properly
/*
 ...
*/

/* USART register Receive complete user callback */
HAL_USART_RegisterRxCpltCallback(&husart, USART_RxCpltCallback);


/* Start a USART Process in DMA mode */
HAL_USART_Receive_DMA(&husart, aRxBuffer,
                             DATA_TO_RECEIVE_SIZE)

Key changes

  1. HAL2 DMA start uses HAL_DMA_StartPeriphXfer_IT_Opt() (optional interrupt generation) instead of HAL_DMA_Start_IT().

  2. HAL2 provides a dedicated registration API for RX completion callbacks: HAL_USART_RegisterRxCpltCallback().