diff --git a/stmhal/hal/f4/inc/stm32f4xx_hal_sd.h b/stmhal/hal/f4/inc/stm32f4xx_hal_sd.h
index 4d4d0326a5..03805b12cd 100644
--- a/stmhal/hal/f4/inc/stm32f4xx_hal_sd.h
+++ b/stmhal/hal/f4/inc/stm32f4xx_hal_sd.h
@@ -663,8 +663,9 @@ void HAL_SD_MspDeInit(SD_HandleTypeDef *hsd);
   * @{
   */
 /* Blocking mode: Polling */
-HAL_SD_ErrorTypedef HAL_SD_ReadBlocks(SD_HandleTypeDef *hsd, uint32_t *pReadBuffer, uint64_t ReadAddr, uint32_t BlockSize, uint32_t NumberOfBlocks);
-HAL_SD_ErrorTypedef HAL_SD_WriteBlocks(SD_HandleTypeDef *hsd, uint32_t *pWriteBuffer, uint64_t WriteAddr, uint32_t BlockSize, uint32_t NumberOfBlocks);
+// dpgeorge: read/write functions renamed to emphasise that address is given by block number
+HAL_SD_ErrorTypedef HAL_SD_ReadBlocks_BlockNumber(SD_HandleTypeDef *hsd, uint32_t *pReadBuffer, uint32_t BlockNumber, uint32_t BlockSize, uint32_t NumberOfBlocks);
+HAL_SD_ErrorTypedef HAL_SD_WriteBlocks_BlockNumber(SD_HandleTypeDef *hsd, uint32_t *pWriteBuffer, uint32_t BlockNumber, uint32_t BlockSize, uint32_t NumberOfBlocks);
 HAL_SD_ErrorTypedef HAL_SD_Erase(SD_HandleTypeDef *hsd, uint64_t startaddr, uint64_t endaddr);
 
 /* Non-Blocking mode: Interrupt */
@@ -679,8 +680,9 @@ void HAL_SD_XferCpltCallback(SD_HandleTypeDef *hsd);
 void HAL_SD_XferErrorCallback(SD_HandleTypeDef *hsd);
 
 /* Non-Blocking mode: DMA */
-HAL_SD_ErrorTypedef HAL_SD_ReadBlocks_DMA(SD_HandleTypeDef *hsd, uint32_t *pReadBuffer, uint64_t ReadAddr, uint32_t BlockSize, uint32_t NumberOfBlocks);
-HAL_SD_ErrorTypedef HAL_SD_WriteBlocks_DMA(SD_HandleTypeDef *hsd, uint32_t *pWriteBuffer, uint64_t WriteAddr, uint32_t BlockSize, uint32_t NumberOfBlocks);
+// dpgeorge: read/write functions renamed to emphasise that address is given by block number
+HAL_SD_ErrorTypedef HAL_SD_ReadBlocks_BlockNumber_DMA(SD_HandleTypeDef *hsd, uint32_t *pReadBuffer, uint32_t BlockNumber, uint32_t BlockSize, uint32_t NumberOfBlocks);
+HAL_SD_ErrorTypedef HAL_SD_WriteBlocks_BlockNumber_DMA(SD_HandleTypeDef *hsd, uint32_t *pWriteBuffer, uint32_t BlockNumber, uint32_t BlockSize, uint32_t NumberOfBlocks);
 HAL_SD_ErrorTypedef HAL_SD_CheckWriteOperation(SD_HandleTypeDef *hsd, uint32_t Timeout);
 HAL_SD_ErrorTypedef HAL_SD_CheckReadOperation(SD_HandleTypeDef *hsd, uint32_t Timeout);
 /**
diff --git a/stmhal/hal/f4/src/stm32f4xx_hal_sd.c b/stmhal/hal/f4/src/stm32f4xx_hal_sd.c
index f70a1fbead..1eb896e1ba 100644
--- a/stmhal/hal/f4/src/stm32f4xx_hal_sd.c
+++ b/stmhal/hal/f4/src/stm32f4xx_hal_sd.c
@@ -461,13 +461,13 @@ __weak void HAL_SD_MspDeInit(SD_HandleTypeDef *hsd)
   *         is managed by polling mode.  
   * @param  hsd: SD handle
   * @param  pReadBuffer: pointer to the buffer that will contain the received data
-  * @param  ReadAddr: Address from where data is to be read  
+  * @param  BlockNumber: Block number from where data is to be read (byte address = BlockNumber * BlockSize)
   * @param  BlockSize: SD card Data block size 
   * @note   BlockSize must be 512 bytes.
   * @param  NumberOfBlocks: Number of SD blocks to read   
   * @retval SD Card error state
   */
-HAL_SD_ErrorTypedef HAL_SD_ReadBlocks(SD_HandleTypeDef *hsd, uint32_t *pReadBuffer, uint64_t ReadAddr, uint32_t BlockSize, uint32_t NumberOfBlocks)
+HAL_SD_ErrorTypedef HAL_SD_ReadBlocks_BlockNumber(SD_HandleTypeDef *hsd, uint32_t *pReadBuffer, uint32_t BlockNumber, uint32_t BlockSize, uint32_t NumberOfBlocks)
 {
   SDIO_CmdInitTypeDef  sdio_cmdinitstructure;
   SDIO_DataInitTypeDef sdio_datainitstructure;
@@ -477,10 +477,16 @@ HAL_SD_ErrorTypedef HAL_SD_ReadBlocks(SD_HandleTypeDef *hsd, uint32_t *pReadBuff
   /* Initialize data control register */
   hsd->Instance->DCTRL = 0U;
   
+  uint32_t ReadAddr;
   if (hsd->CardType == HIGH_CAPACITY_SD_CARD)
   {
-    BlockSize = 512U;
-    ReadAddr /= 512U;
+    BlockSize = 512;
+    ReadAddr = BlockNumber;
+  }
+  else
+  {
+    // should not overflow for standard-capacity cards
+    ReadAddr = BlockNumber * BlockSize;
   }
   
   /* Set Block Size for Card */ 
@@ -519,7 +525,7 @@ HAL_SD_ErrorTypedef HAL_SD_ReadBlocks(SD_HandleTypeDef *hsd, uint32_t *pReadBuff
     sdio_cmdinitstructure.CmdIndex = SD_CMD_READ_SINGLE_BLOCK;    
   }
   
-  sdio_cmdinitstructure.Argument         = (uint32_t)ReadAddr;
+  sdio_cmdinitstructure.Argument         = ReadAddr;
   SDIO_SendCommand(hsd->Instance, &sdio_cmdinitstructure);
   
   /* Read block(s) in polling mode */
@@ -655,13 +661,13 @@ HAL_SD_ErrorTypedef HAL_SD_ReadBlocks(SD_HandleTypeDef *hsd, uint32_t *pReadBuff
   *         transfer is managed by polling mode.  
   * @param  hsd: SD handle
   * @param  pWriteBuffer: pointer to the buffer that will contain the data to transmit
-  * @param  WriteAddr: Address from where data is to be written 
+  * @param  BlockNumber: Block number to where data is to be written (byte address = BlockNumber * BlockSize)
   * @param  BlockSize: SD card Data block size 
   * @note   BlockSize must be 512 bytes.
   * @param  NumberOfBlocks: Number of SD blocks to write 
   * @retval SD Card error state
   */
-HAL_SD_ErrorTypedef HAL_SD_WriteBlocks(SD_HandleTypeDef *hsd, uint32_t *pWriteBuffer, uint64_t WriteAddr, uint32_t BlockSize, uint32_t NumberOfBlocks)
+HAL_SD_ErrorTypedef HAL_SD_WriteBlocks_BlockNumber(SD_HandleTypeDef *hsd, uint32_t *pWriteBuffer, uint32_t BlockNumber, uint32_t BlockSize, uint32_t NumberOfBlocks)
 {
   SDIO_CmdInitTypeDef sdio_cmdinitstructure;
   SDIO_DataInitTypeDef sdio_datainitstructure;
@@ -673,10 +679,16 @@ HAL_SD_ErrorTypedef HAL_SD_WriteBlocks(SD_HandleTypeDef *hsd, uint32_t *pWriteBu
   /* Initialize data control register */
   hsd->Instance->DCTRL = 0U;
   
+  uint32_t WriteAddr;
   if (hsd->CardType == HIGH_CAPACITY_SD_CARD)
   {
-    BlockSize = 512U;
-    WriteAddr /= 512U;
+    BlockSize = 512;
+    WriteAddr = BlockNumber;
+  }
+  else
+  {
+    // should not overflow for standard-capacity cards
+    WriteAddr = BlockNumber * BlockSize;
   }
   
   /* Set Block Size for Card */ 
@@ -706,7 +718,7 @@ HAL_SD_ErrorTypedef HAL_SD_WriteBlocks(SD_HandleTypeDef *hsd, uint32_t *pWriteBu
     sdio_cmdinitstructure.CmdIndex = SD_CMD_WRITE_SINGLE_BLOCK;
   }
   
-  sdio_cmdinitstructure.Argument         = (uint32_t)WriteAddr;
+  sdio_cmdinitstructure.Argument         = WriteAddr;
   SDIO_SendCommand(hsd->Instance, &sdio_cmdinitstructure);
   
   /* Check for error conditions */
@@ -883,13 +895,13 @@ HAL_SD_ErrorTypedef HAL_SD_WriteBlocks(SD_HandleTypeDef *hsd, uint32_t *pWriteBu
   *         to check the completion of the read process   
   * @param  hsd: SD handle                 
   * @param  pReadBuffer: Pointer to the buffer that will contain the received data
-  * @param  ReadAddr: Address from where data is to be read  
+  * @param  BlockNumber: Block number from where data is to be read (byte address = BlockNumber * BlockSize)
   * @param  BlockSize: SD card Data block size 
   * @note   BlockSize must be 512 bytes.
   * @param  NumberOfBlocks: Number of blocks to read.
   * @retval SD Card error state
   */
-HAL_SD_ErrorTypedef HAL_SD_ReadBlocks_DMA(SD_HandleTypeDef *hsd, uint32_t *pReadBuffer, uint64_t ReadAddr, uint32_t BlockSize, uint32_t NumberOfBlocks)
+HAL_SD_ErrorTypedef HAL_SD_ReadBlocks_BlockNumber_DMA(SD_HandleTypeDef *hsd, uint32_t *pReadBuffer, uint32_t BlockNumber, uint32_t BlockSize, uint32_t NumberOfBlocks)
 {
   SDIO_CmdInitTypeDef sdio_cmdinitstructure;
   SDIO_DataInitTypeDef sdio_datainitstructure;
@@ -937,10 +949,16 @@ HAL_SD_ErrorTypedef HAL_SD_ReadBlocks_DMA(SD_HandleTypeDef *hsd, uint32_t *pRead
   /* Enable the DMA Stream */
   HAL_DMA_Start_IT(hsd->hdmarx, (uint32_t)&hsd->Instance->FIFO, (uint32_t)pReadBuffer, (uint32_t)(BlockSize * NumberOfBlocks)/4);
   
+  uint32_t ReadAddr;
   if (hsd->CardType == HIGH_CAPACITY_SD_CARD)
   {
-    BlockSize = 512U;
-    ReadAddr /= 512U;
+    BlockSize = 512;
+    ReadAddr = BlockNumber;
+  }
+  else
+  {
+    // should not overflow for standard-capacity cards
+    ReadAddr = BlockNumber * BlockSize;
   }
   
   /* Set Block Size for Card */ 
@@ -980,7 +998,7 @@ HAL_SD_ErrorTypedef HAL_SD_ReadBlocks_DMA(SD_HandleTypeDef *hsd, uint32_t *pRead
     sdio_cmdinitstructure.CmdIndex = SD_CMD_READ_SINGLE_BLOCK;
   }
   
-  sdio_cmdinitstructure.Argument = (uint32_t)ReadAddr;
+  sdio_cmdinitstructure.Argument         = ReadAddr;
   SDIO_SendCommand(hsd->Instance, &sdio_cmdinitstructure);
   
   /* Check for error conditions */
@@ -1007,13 +1025,13 @@ HAL_SD_ErrorTypedef HAL_SD_ReadBlocks_DMA(SD_HandleTypeDef *hsd, uint32_t *pRead
   *         to check the completion of the write process (by SD current status polling).  
   * @param  hsd: SD handle
   * @param  pWriteBuffer: pointer to the buffer that will contain the data to transmit
-  * @param  WriteAddr: Address from where data is to be read   
+  * @param  BlockNumber: Block number to where data is to be written (byte address = BlockNumber * BlockSize)
   * @param  BlockSize: the SD card Data block size 
   * @note   BlockSize must be 512 bytes.
   * @param  NumberOfBlocks: Number of blocks to write
   * @retval SD Card error state
   */
-HAL_SD_ErrorTypedef HAL_SD_WriteBlocks_DMA(SD_HandleTypeDef *hsd, uint32_t *pWriteBuffer, uint64_t WriteAddr, uint32_t BlockSize, uint32_t NumberOfBlocks)
+HAL_SD_ErrorTypedef HAL_SD_WriteBlocks_BlockNumber_DMA(SD_HandleTypeDef *hsd, uint32_t *pWriteBuffer, uint32_t BlockNumber, uint32_t BlockSize, uint32_t NumberOfBlocks)
 {
   SDIO_CmdInitTypeDef sdio_cmdinitstructure;
   SDIO_DataInitTypeDef sdio_datainitstructure;
@@ -1061,10 +1079,16 @@ HAL_SD_ErrorTypedef HAL_SD_WriteBlocks_DMA(SD_HandleTypeDef *hsd, uint32_t *pWri
   /* Enable SDIO DMA transfer */
   __HAL_SD_SDIO_DMA_ENABLE();
   
+  uint32_t WriteAddr;
   if (hsd->CardType == HIGH_CAPACITY_SD_CARD)
   {
-    BlockSize = 512U;
-    WriteAddr /= 512U;
+    BlockSize = 512;
+    WriteAddr = BlockNumber;
+  }
+  else
+  {
+    // should not overflow for standard-capacity cards
+    WriteAddr = BlockNumber * BlockSize;
   }
 
   /* Set Block Size for Card */ 
@@ -1095,7 +1119,7 @@ HAL_SD_ErrorTypedef HAL_SD_WriteBlocks_DMA(SD_HandleTypeDef *hsd, uint32_t *pWri
     sdio_cmdinitstructure.CmdIndex = SD_CMD_WRITE_MULT_BLOCK;
   }
   
-  sdio_cmdinitstructure.Argument         = (uint32_t)WriteAddr;
+  sdio_cmdinitstructure.Argument         = WriteAddr;
   SDIO_SendCommand(hsd->Instance, &sdio_cmdinitstructure);
 
   /* Check for error conditions */