1.25.19 1.26.17 1.27.19 1.28.22 Secure Digital MultiMedia Card Controller (SDMMC)
The SDMMC PLIB provides low level APIs to configure and transfer data using the SD host controller. The SDMMC PLIB supports SDMMC and eMMC modes, default and high speed data transfer, 1/4/8 bit data bus configurations. The PLIB performs the transfers in non-blocking mode. Transfers involving a data stage are performed using DMA.
Using The Library
The example code demonstrates sending a SD command to read a single block of data from the SD card. This example assumes that the SD card is already initialized by the application and is ready to accept read and write requests. The example application does not show the larger SD protocol required in order to communicate with the SD card.
uint16_t data_error; bool isCommandCompleted = false; bool isDataCompleted = false; uint8_t readBuffer[512]; static void SDMMC_TransferEventHandler( SDMMC_XFER_STATUS xferStatus, uintptr_t contextHandle ) { if (xferStatus & SDMMC_XFER_STATUS_CMD_COMPLETED) { // Command transfer complete, read the command error status. cmd_error = SDMMC1_CommandErrorGet(); isCommandCompleted = true; } if (xferStatus & SDMMC_XFER_STATUS_DATA_COMPLETED) { // Data transfer complete, read the data error status. data_error = SDMMC1_DataErrorGet(); isDataCompleted = true; } } int main(void) { // Register event handler with the SDMMC PLIB. This is usually done once. SDMMC1_CallbackRegister(SDMMC_TransferEventHandler, (uintptr_t) 0); SDMMC_DataTransferFlags transferFlags; transferFlags.isDataPresent = true; transferFlags.transferDir = SDMMC_DATA_TRANSFER_DIR_READ; transferFlags.transferType = SDMMC_DATA_TRANSFER_TYPE_SINGLE; // Set the block size to 512 bytes SDMMC1_BlockSizeSet(512); // Set the block count to 1 SDMMC1_BlockCountSet(1); // Set up the DMA to read 512 btyes of data SDMMC1_DmaSetup(readBuffer, 512, SDMMC_DATA_TRANSFER_DIR_READ); // Send command to read one block of data from SD card starting at block address 100 SDMMC1_CommandSend(17, 100, SDMMC_CMD_RESP_R1, transferFlags); // Check the status of isCommandCompleted and isDataCompleted // Other tasks ... }
Library Interface
SD/MMC Host Controller peripheral library provides the following interfaces:
Functions
Name | Description |
---|---|
SDMMCx_BusWidthSet | Configures the width of the data bus |
SDMMCx_SpeedModeSet | Sets the bus speed |
SDMMCx_BlockSizeSet | Sets the size of the one data block of transfer |
SDMMCx_BlockCountSet | Sets the number of blocks to transfer |
SDMMCx_IsCmdLineBusy | Returns the status of the command line |
SDMMCx_IsDatLineBusy | Returns the status of the data line |
SDMMCx_IsWriteProtected | Returns the write protect switch pin level |
SDMMCx_IsCardAttached | Indicates if the card is attached or detached |
SDMMCx_ClockSet | Sets the SDMMC clock frequency |
SDMMCx_ClockEnable | Enable SDMMC clock |
SDMMCx_ClockDisable | Disable SDMMC clock |
SDMMCx_CommandErrorGet | Returns the errors associated with a command transfer |
SDMMCx_DataErrorGet | Returns the errors associated with a data transfer |
SDMMCx_ErrorReset | Resets errors as specified by the resetType |
SDMMCx_ResponseRead | Reads the response to a given command |
SDMMCx_ModuleInit | Initializes the SDMMC peripheral |
SDMMCx_Initialize | Initializes the SDMMC peripheral and the internal data structures used by the peripheral library |
SDMMCx_CallbackRegister | This function allows a SDMMC PLIB client to set an event handler |
SDMMCx_CommandSend | This function allows the client to send a SD command on the SDMMC interface |
SDMMCx_DmaSetup | Sets up the DMA for data tranfers |
Data types and constants
Name | Type | Description |
---|---|---|
SDMMC_BUS_WIDTH | Enum | The enumeration lists the bus widths for the SDMMC bus |
SDMMC_SPEED_MODE | Enum | The enumeration lists the bus widths for the SDMMC bus |
SDMMC_READ_RESPONSE_REG | Enum | The enumeration lists the response registers that can be read for a given command |
SDMMC_RESET_TYPE | Enum | The enumeration lists error type to reset |
SDMMC_XFER_STATUS | Enum | The enumeration lists the status of the transfer |
SDMMC_DATA_TRANSFER_DIR | Enum | The enumeration lists the direction of the data transfer |
SDMMC_DataTransferFlags | Struct | The data structure is used by the client to provide information about the data trasnfer to the SDMMC PLIB |
SDMMC_CALLBACK | Typedef | The prototype of the SDMMC callback function |