DMADRV - DMA Driver#

Direct Memory Access Driver.


Introduction#

The DMADRV driver supports writing code using DMA which will work regardless of the type of the DMA controller on the underlying microcontroller. Additionally, DMA can be used in several modules that are completely unaware of each other. The driver does not preclude use of the native emlib or peripheral API of the underlying DMA controller. On the contrary, it will often result in more efficient code and is necessary for complex DMA operations. The housekeeping functions of this driver are valuable even in this use-case.

The dmadrv.c and dmadrv.h source files are in the emdrv/dmadrv folder.

Note

  • DMA transfer completion callback functions are called from within the DMA interrupt handler. On versions of the DMA controller with one interrupt per channel, the callback function is called from its respective channel interrupt handler.


Configuration Options#

Some properties of the DMADRV driver are compile-time configurable. These properties are stored in a file named dmadrv_config.h. A template for this file, containing default values, is in the emdrv/config folder. IC specific versions of dmadrv_config.h files are available in config/sx_xch directories. Currently the configuration options are as follows:

  • The interrupt priority of the DMA peripheral.

  • A number of DMA channels to support.

  • Use the native emlib/peripheral API belonging to the underlying DMA hardware in combination with the DMADRV API.

Both configuration options will help reduce the driver's RAM footprint.

To configure DMADRV, provide a custom configuration file. This is an example dmadrv_config.h file:

#ifndef __SILICON_LABS_DMADRV_CONFIG_H__
#define __SILICON_LABS_DMADRV_CONFIG_H__

  // DMADRV DMA interrupt priority configuration option.
  // Set DMA interrupt priority. Range is 0..7, 0 is the highest priority.
#define EMDRV_DMADRV_DMA_IRQ_PRIORITY 4

  // DMADRV channel count configuration option.
  // A number of DMA channels to support. A lower DMA channel count will reduce
  // RAM footprint.
#define EMDRV_DMADRV_DMA_CH_COUNT 4

#endif


The API#

This section contains brief descriptions of the API functions. For more information about input and output parameters and return values, click on the hyperlinked function names. Most functions return an error code, ECODE_EMDRV_DMADRV_OK is returned on success, see ECODE - Error Codes and Error Codes for other error codes.

The application code must include dmadrv.h header file.

DMADRV_Init(), DMADRV_DeInit()
These functions initialize or deinitialize the DMADRV driver. Typically, DMADRV_Init() is called once in the startup code.

DMADRV_AllocateChannel(), DMADRV_FreeChannel()
DMA channel reserve and release functions. It is recommended that application code check that DMADRV_AllocateChannel() returns ECODE_EMDRV_DMADRV_OK before starting a DMA transfer.

DMADRV_MemoryPeripheral()
Start a DMA transfer from memory to a peripheral.

DMADRV_PeripheralMemory()
Start a DMA transfer from a peripheral to memory.

DMADRV_MemoryPeripheralPingPong()
Start a DMA ping-pong transfer from memory to a peripheral.

DMADRV_PeripheralMemoryPingPong()
Start a DMA ping-pong transfer from a peripheral to memory.

DMADRV_LdmaStartTransfer()
Start a DMA transfer on an LDMA controller.

DMADRV_PauseTransfer()
Pause an ongoing DMA transfer.

DMADRV_ResumeTransfer()
Resume paused DMA transfer.

DMADRV_StopTransfer()
Stop an ongoing DMA transfer.

DMADRV_TransferActive()
Check if a transfer is ongoing.

DMADRV_TransferCompletePending()
Check if a transfer completion is pending.

DMADRV_TransferDone()
Check if a transfer has completed.

DMADRV_TransferRemainingCount()
Get number of items remaining in a transfer.


Example#

Transfer a text string to USART1.

#include "dmadrv.h"

  char str[] = "Hello DMA !";
  unsigned int channel;

  int main( void )
  {
  // Initialize DMA.
  DMADRV_Init();

  // Request a DMA channel.
  DMADRV_AllocateChannel( &channel, NULL );

  // Start the DMA transfer.
  DMADRV_MemoryPeripheral( channel,
                          dmadrvPeripheralSignal_USART1_TXBL,
                          (void*)&(USART1->TXDATA),
                          str,
                          true,
                          sizeof( str ),
                          dmadrvDataSize1,
                          NULL,
                          NULL );

  return 0;
  }

Modules#

Error Codes

Typedefs#

typedef bool(*
DMADRV_Callback_t)(unsigned int channel, unsigned int sequenceNo, void *userParam)

DMADRV transfer completion callback function.

Functions#

DMADRV_AllocateChannel(unsigned int *channelId, void *capabilities)

Allocate (reserve) a DMA channel.

Deinitialize DMADRV.

DMADRV_FreeChannel(unsigned int channelId)

Free an allocated (reserved) DMA channel.

Initialize DMADRV.

DMADRV_MemoryPeripheral(unsigned int channelId, DMADRV_PeripheralSignal_t peripheralSignal, void *dst, void *src, bool srcInc, int len, DMADRV_DataSize_t size, DMADRV_Callback_t callback, void *cbUserParam)

Start a memory to a peripheral DMA transfer.

DMADRV_PeripheralMemory(unsigned int channelId, DMADRV_PeripheralSignal_t peripheralSignal, void *dst, void *src, bool dstInc, int len, DMADRV_DataSize_t size, DMADRV_Callback_t callback, void *cbUserParam)

Start a peripheral to memory DMA transfer.

DMADRV_MemoryPeripheralPingPong(unsigned int channelId, DMADRV_PeripheralSignal_t peripheralSignal, void *dst, void *src0, void *src1, bool srcInc, int len, DMADRV_DataSize_t size, DMADRV_Callback_t callback, void *cbUserParam)

Start a memory to a peripheral ping-pong DMA transfer.

DMADRV_PeripheralMemoryPingPong(unsigned int channelId, DMADRV_PeripheralSignal_t peripheralSignal, void *dst0, void *dst1, void *src, bool dstInc, int len, DMADRV_DataSize_t size, DMADRV_Callback_t callback, void *cbUserParam)

Start a peripheral to memory ping-pong DMA transfer.

DMADRV_LdmaStartTransfer(int channelId, LDMA_TransferCfg_t *transfer, LDMA_Descriptor_t *descriptor, DMADRV_Callback_t callback, void *cbUserParam)

Start an LDMA transfer.

DMADRV_PauseTransfer(unsigned int channelId)

Pause an ongoing DMA transfer.

DMADRV_ResumeTransfer(unsigned int channelId)

Resume an ongoing DMA transfer.

DMADRV_StopTransfer(unsigned int channelId)

Stop an ongoing DMA transfer.

DMADRV_TransferActive(unsigned int channelId, bool *active)

Check if a transfer is running.

DMADRV_TransferCompletePending(unsigned int channelId, bool *pending)

Check if a transfer complete is pending.

DMADRV_TransferDone(unsigned int channelId, bool *done)

Check if a transfer has completed.

DMADRV_TransferRemainingCount(unsigned int channelId, int *remaining)

Get number of items remaining in a transfer.

Typedef Documentation#

DMADRV_Callback_t#

typedef bool(* DMADRV_Callback_t) (unsigned int channel, unsigned int sequenceNo, void *userParam) )(unsigned int channel, unsigned int sequenceNo, void *userParam)

DMADRV transfer completion callback function.

Parameters
[in]channel

The DMA channel number.

[in]sequenceNo

The number of times the callback was called. Useful on long chains of linked transfers or on endless ping-pong type transfers.

[in]userParam

Optional user parameter supplied on DMA invocation.

The callback function is called when a transfer is complete.

Returns

  • When doing ping-pong transfers, return true to continue or false to stop transfers.


Definition at line 98 of file platform/emdrv/dmadrv/inc/dmadrv.h

Function Documentation#

DMADRV_AllocateChannel#

Ecode_t DMADRV_AllocateChannel (unsigned int * channelId, void * capabilities)

Allocate (reserve) a DMA channel.

Parameters
[out]channelId

The channel ID assigned by DMADRV.

[in]capabilities

Not used.

Returns


Definition at line 102 of file platform/emdrv/dmadrv/inc/dmadrv.h

DMADRV_DeInit#

Ecode_t DMADRV_DeInit (void )

Deinitialize DMADRV.

Parameters
N/A

If DMA channels are not currently allocated, it will disable DMA hardware and mask associated interrupts.

Returns


Definition at line 104 of file platform/emdrv/dmadrv/inc/dmadrv.h

DMADRV_FreeChannel#

Ecode_t DMADRV_FreeChannel (unsigned int channelId)

Free an allocated (reserved) DMA channel.

Parameters
[in]channelId

The channel ID to free.

Returns


Definition at line 105 of file platform/emdrv/dmadrv/inc/dmadrv.h

DMADRV_Init#

Ecode_t DMADRV_Init (void )

Initialize DMADRV.

Parameters
N/A

The DMA hardware is initialized.

Returns


Definition at line 106 of file platform/emdrv/dmadrv/inc/dmadrv.h

DMADRV_MemoryPeripheral#

Ecode_t DMADRV_MemoryPeripheral (unsigned int channelId, DMADRV_PeripheralSignal_t peripheralSignal, void * dst, void * src, bool srcInc, int len, DMADRV_DataSize_t size, DMADRV_Callback_t callback, void * cbUserParam)

Start a memory to a peripheral DMA transfer.

Parameters
[in]channelId

The channel ID to use for the transfer.

[in]peripheralSignal

Selects which peripheral/peripheralsignal to use.

[in]dst

A destination (peripheral register) memory address.

[in]src

A source memory address.

[in]srcInc

Set to true to enable source address increment (increments according to size parameter).

[in]len

A number of items (of size size) to transfer.

[in]size

An item size, byte, halfword or word.

[in]callback

A function to call on DMA completion, use NULL if not needed.

[in]cbUserParam

An optional user parameter to feed to the callback function. Use NULL if not needed.

Returns


Definition at line 108 of file platform/emdrv/dmadrv/inc/dmadrv.h

DMADRV_PeripheralMemory#

Ecode_t DMADRV_PeripheralMemory (unsigned int channelId, DMADRV_PeripheralSignal_t peripheralSignal, void * dst, void * src, bool dstInc, int len, DMADRV_DataSize_t size, DMADRV_Callback_t callback, void * cbUserParam)

Start a peripheral to memory DMA transfer.

Parameters
[in]channelId

The channel ID to use for the transfer.

[in]peripheralSignal

Selects which peripheral/peripheralsignal to use.

[in]dst

A destination memory address.

[in]src

A source memory (peripheral register) address.

[in]dstInc

Set to true to enable destination address increment (increments according to size parameter).

[in]len

A number of items (of size size) to transfer.

[in]size

An item size, byte, halfword or word.

[in]callback

A function to call on DMA completion, use NULL if not needed.

[in]cbUserParam

An optional user parameter to feed to the callback function. Use NULL if not needed.

Returns


Definition at line 117 of file platform/emdrv/dmadrv/inc/dmadrv.h

DMADRV_MemoryPeripheralPingPong#

Ecode_t DMADRV_MemoryPeripheralPingPong (unsigned int channelId, DMADRV_PeripheralSignal_t peripheralSignal, void * dst, void * src0, void * src1, bool srcInc, int len, DMADRV_DataSize_t size, DMADRV_Callback_t callback, void * cbUserParam)

Start a memory to a peripheral ping-pong DMA transfer.

Parameters
[in]channelId

The channel ID to use for the transfer.

[in]peripheralSignal

Selects which peripheral/peripheralsignal to use.

[in]dst

A destination (peripheral register) memory address.

[in]src0

A source memory address of the first (ping) buffer.

[in]src1

A source memory address of the second (pong) buffer.

[in]srcInc

Set to true to enable source address increment (increments according to size parameter).

[in]len

A number of items (of size size) to transfer.

[in]size

An item size, byte, halfword or word.

[in]callback

A function to call on DMA completion, use NULL if not needed.

[in]cbUserParam

An optional user parameter to feed to the callback function. Use NULL if not needed.

Returns


Definition at line 126 of file platform/emdrv/dmadrv/inc/dmadrv.h

DMADRV_PeripheralMemoryPingPong#

Ecode_t DMADRV_PeripheralMemoryPingPong (unsigned int channelId, DMADRV_PeripheralSignal_t peripheralSignal, void * dst0, void * dst1, void * src, bool dstInc, int len, DMADRV_DataSize_t size, DMADRV_Callback_t callback, void * cbUserParam)

Start a peripheral to memory ping-pong DMA transfer.

Parameters
[in]channelId

The channel ID to use for the transfer.

[in]peripheralSignal

Selects which peripheral/peripheralsignal to use.

[in]dst0

A destination memory address of the first (ping) buffer.

[in]dst1

A destination memory address of the second (pong) buffer.

[in]src

A source memory (peripheral register) address.

[in]dstInc

Set to true to enable destination address increment (increments according to size parameter).

[in]len

A number of items (of size size) to transfer.

[in]size

An item size, byte, halfword or word.

[in]callback

A function to call on DMA completion, use NULL if not needed.

[in]cbUserParam

An optional user parameter to feed to the callback function. Use NULL if not needed.

Returns


Definition at line 136 of file platform/emdrv/dmadrv/inc/dmadrv.h

DMADRV_LdmaStartTransfer#

Ecode_t DMADRV_LdmaStartTransfer (int channelId, LDMA_TransferCfg_t * transfer, LDMA_Descriptor_t * descriptor, DMADRV_Callback_t callback, void * cbUserParam)

Start an LDMA transfer.

Parameters
[in]channelId

The channel ID to use.

[in]transfer

A DMA transfer configuration data structure.

[in]descriptor

A DMA transfer descriptor, can be an array of descriptors linked together.

[in]callback

An optional callback function for signalling completion. May be NULL if not needed.

[in]cbUserParam

An optional user parameter to feed to the callback function. May be NULL if not needed.

This function is similar to the emlib LDMA function.

Returns


Definition at line 148 of file platform/emdrv/dmadrv/inc/dmadrv.h

DMADRV_PauseTransfer#

Ecode_t DMADRV_PauseTransfer (unsigned int channelId)

Pause an ongoing DMA transfer.

Parameters
[in]channelId

The channel ID of the transfer to pause.

Returns


Definition at line 155 of file platform/emdrv/dmadrv/inc/dmadrv.h

DMADRV_ResumeTransfer#

Ecode_t DMADRV_ResumeTransfer (unsigned int channelId)

Resume an ongoing DMA transfer.

Parameters
[in]channelId

The channel ID of the transfer to resume.

Returns


Definition at line 156 of file platform/emdrv/dmadrv/inc/dmadrv.h

DMADRV_StopTransfer#

Ecode_t DMADRV_StopTransfer (unsigned int channelId)

Stop an ongoing DMA transfer.

Parameters
[in]channelId

The channel ID of the transfer to stop.

Returns


Definition at line 157 of file platform/emdrv/dmadrv/inc/dmadrv.h

DMADRV_TransferActive#

Ecode_t DMADRV_TransferActive (unsigned int channelId, bool * active)

Check if a transfer is running.

Parameters
[in]channelId

The channel ID of the transfer to check.

[out]active

True if transfer is running, false otherwise.

Returns


Definition at line 158 of file platform/emdrv/dmadrv/inc/dmadrv.h

DMADRV_TransferCompletePending#

Ecode_t DMADRV_TransferCompletePending (unsigned int channelId, bool * pending)

Check if a transfer complete is pending.

Parameters
[in]channelId

The channel ID of the transfer to check.

[out]pending

True if a transfer complete is pending, false otherwise.

Will check the channel interrupt flag. This assumes that the DMA is configured to give a completion interrupt.

Returns


Definition at line 160 of file platform/emdrv/dmadrv/inc/dmadrv.h

DMADRV_TransferDone#

Ecode_t DMADRV_TransferDone (unsigned int channelId, bool * done)

Check if a transfer has completed.

Parameters
[in]channelId

The channel ID of the transfer to check.

[out]done

True if a transfer has completed, false otherwise.

Note

  • This function should be used in a polled environment. Will only work reliably for transfers NOT using the completion interrupt. On UDMA, it will only work on basic transfers on the primary channel.

Returns


Definition at line 162 of file platform/emdrv/dmadrv/inc/dmadrv.h

DMADRV_TransferRemainingCount#

Ecode_t DMADRV_TransferRemainingCount (unsigned int channelId, int * remaining)

Get number of items remaining in a transfer.

Parameters
[in]channelId

The channel ID of the transfer to check.

[out]remaining

A number of items remaining in the transfer.

Note

  • This function does not take into account that a DMA transfer with a chain of linked transfers might be ongoing. It will only check the count for the current transfer. On UDMA, it will only work on the primary channel.

Returns


Definition at line 164 of file platform/emdrv/dmadrv/inc/dmadrv.h