DMA
[EM_Library]

Direct Memory Access (DMA) Peripheral API. More...

Collaboration diagram for DMA:

Data Structures

struct  DMA_CB_TypeDef
 Callback structure that can be used to define DMA complete actions. More...
struct  DMA_CfgChannel_TypeDef
struct  DMA_CfgDescr_TypeDef
struct  DMA_CfgDescrSGAlt_TypeDef
struct  DMA_Init_TypeDef

Typedefs

typedef void(* DMA_FuncPtr_TypeDef )(unsigned int channel, bool primary, void *user)
 DMA interrupt callback function pointer.

Enumerations

enum  DMA_DataInc_TypeDef {
  dmaDataInc1 = _DMA_CTRL_SRC_INC_BYTE,
  dmaDataInc2 = _DMA_CTRL_SRC_INC_HALFWORD,
  dmaDataInc4 = _DMA_CTRL_SRC_INC_WORD,
  dmaDataIncNone = _DMA_CTRL_SRC_INC_NONE
}
enum  DMA_DataSize_TypeDef {
  dmaDataSize1 = _DMA_CTRL_SRC_SIZE_BYTE,
  dmaDataSize2 = _DMA_CTRL_SRC_SIZE_HALFWORD,
  dmaDataSize4 = _DMA_CTRL_SRC_SIZE_WORD
}
enum  DMA_CycleCtrl_TypeDef {
  dmaCycleCtrlBasic = _DMA_CTRL_CYCLE_CTRL_BASIC,
  dmaCycleCtrlAuto = _DMA_CTRL_CYCLE_CTRL_AUTO,
  dmaCycleCtrlPingPong = _DMA_CTRL_CYCLE_CTRL_PINGPONG,
  dmaCycleCtrlMemScatterGather = _DMA_CTRL_CYCLE_CTRL_MEM_SCATTER_GATHER,
  dmaCycleCtrlPerScatterGather = _DMA_CTRL_CYCLE_CTRL_PER_SCATTER_GATHER
}
enum  DMA_ArbiterConfig_TypeDef {
  dmaArbitrate1 = _DMA_CTRL_R_POWER_1,
  dmaArbitrate2 = _DMA_CTRL_R_POWER_2,
  dmaArbitrate4 = _DMA_CTRL_R_POWER_4,
  dmaArbitrate8 = _DMA_CTRL_R_POWER_8,
  dmaArbitrate16 = _DMA_CTRL_R_POWER_16,
  dmaArbitrate32 = _DMA_CTRL_R_POWER_32,
  dmaArbitrate64 = _DMA_CTRL_R_POWER_64,
  dmaArbitrate128 = _DMA_CTRL_R_POWER_128,
  dmaArbitrate256 = _DMA_CTRL_R_POWER_256,
  dmaArbitrate512 = _DMA_CTRL_R_POWER_512,
  dmaArbitrate1024 = _DMA_CTRL_R_POWER_1024
}

Functions

void DMA_ActivateAuto (unsigned int channel, bool primary, void *dst, void *src, unsigned int nMinus1)
 Activate DMA auto-request cycle (used for memory-memory transfers).
void DMA_ActivateBasic (unsigned int channel, bool primary, bool useBurst, void *dst, void *src, unsigned int nMinus1)
 Activate DMA basic cycle (used for memory-peripheral transfers).
void DMA_ActivatePingPong (unsigned int channel, bool useBurst, void *primDst, void *primSrc, unsigned int primNMinus1, void *altDst, void *altSrc, unsigned int altNMinus1)
 Activate DMA ping-pong cycle (used for memory-peripheral transfers).
void DMA_ActivateScatterGather (unsigned int channel, bool useBurst, DMA_DESCRIPTOR_TypeDef *altDescr, unsigned int count)
 Activate DMA scatter-gather cycle (used for either memory-peripheral or memory-memory transfers).
void DMA_CfgChannel (unsigned int channel, DMA_CfgChannel_TypeDef *cfg)
 Configure a DMA channel.
void DMA_CfgDescr (unsigned int channel, bool primary, DMA_CfgDescr_TypeDef *cfg)
 Configure DMA descriptor for auto-request, basic or ping-pong DMA cycles.
void DMA_CfgDescrScatterGather (DMA_DESCRIPTOR_TypeDef *descr, unsigned int indx, DMA_CfgDescrSGAlt_TypeDef *cfg)
 Configure an alternate DMA descriptor for use with scatter-gather DMA cycles.
void DMA_ChannelEnable (unsigned int channel, bool enable)
 Enable or disable a DMA channel.
bool DMA_ChannelEnabled (unsigned int channel)
 Check if DMA channel is enabled.
void DMA_Init (DMA_Init_TypeDef *init)
 Initializes DMA controller.
void DMA_IRQHandler (void)
 Interrupt handler for DMA cycle completion handling.
void DMA_RefreshPingPong (unsigned int channel, bool primary, bool useBurst, void *dst, void *src, unsigned int nMinus1, bool stop)
 Refresh a descriptor used in a DMA ping-pong cycle.
void DMA_Reset (void)
 Reset the DMA controller.

Detailed Description

Direct Memory Access (DMA) Peripheral API.

These DMA access functions provide basic support for the following types of DMA cycles:

A basic understanding of the DMA controller is assumed. Please refer to the EFM32 reference manual for further details.

The term 'descriptor' is used as a synonym to the 'channel control data structure' term.

In order to use the DMA controller, the initialization function must have been executed once (normally during system init):

 * DMA_Init();
 * 

Then, normally a user of a DMA channel configures the channel:

 * DMA_CfgChannel();
 * 

The channel configuration only has to be done once, if reusing the channel for the same purpose later.

In order to set up a DMA cycle, the primary and/or alternate descriptor has to be set up as indicated below.

For basic or auto-request cycles, use once on either primary or alternate descriptor:

 * DMA_CfgDescr();
 * 

For ping-pong cycles, configure both primary or alternate descriptors:

 * DMA_CfgDescr(); // Primary descriptor config
 * DMA_CfgDescr(); // Alternate descriptor config
 * 

For scatter-gather cycles, the alternate descriptor array must be programmed:

 * // 'n' is the number of scattered buffers
 * // 'descr' points to the start of the alternate descriptor array
 *
 * // Fill in 'cfg'
 * DMA_CfgDescrScatterGather(descr, 0, cfg);
 * // Fill in 'cfg'
 * DMA_CfgDescrScatterGather(descr, 1, cfg);
 * :
 * // Fill in 'cfg'
 * DMA_CfgDescrScatterGather(descr, n - 1, cfg);
 * 

In many cases, the descriptor configuration only has to be done once, if re-using the channel for the same type of DMA cycles later.

In order to activate the DMA cycle, use the respective DMA_Activate...() function.

For ping-pong DMA cycles, use DMA_RefreshPingPong() from the callback to prepare the completed descriptor for reuse. Notice that the refresh must be done prior to the other active descriptor completes, otherwise the ping-pong DMA cycle will halt.


Typedef Documentation

typedef void(* DMA_FuncPtr_TypeDef)(unsigned int channel, bool primary, void *user)

DMA interrupt callback function pointer.

Parameters:

  • channel - The DMA channel the callback function is invoked for.
  • primary - Indicates if callback is invoked for completion of primary (true) or alternate (false) descriptor. This is mainly useful for ping-pong DMA cycles, in order to know which descriptor to refresh.
  • user - User definable reference that may be used to pass information to be used by the callback handler. If used, the referenced data must be valid at the point when the interrupt handler invokes the callback. If callback changes any data in the provided user structure, remember that those changes are done in interrupt context, and proper protection of data may be required.

Definition at line 137 of file em_dma.h.


Enumeration Type Documentation

Number of transfers before controller does new arbitration.

Enumerator:
dmaArbitrate1 

Arbitrate after 1 DMA transfer.

dmaArbitrate2 

Arbitrate after 2 DMA transfers.

dmaArbitrate4 

Arbitrate after 4 DMA transfers.

dmaArbitrate8 

Arbitrate after 8 DMA transfers.

dmaArbitrate16 

Arbitrate after 16 DMA transfers.

dmaArbitrate32 

Arbitrate after 32 DMA transfers.

dmaArbitrate64 

Arbitrate after 64 DMA transfers.

dmaArbitrate128 

Arbitrate after 128 DMA transfers.

dmaArbitrate256 

Arbitrate after 256 DMA transfers.

dmaArbitrate512 

Arbitrate after 512 DMA transfers.

dmaArbitrate1024 

Arbitrate after 1024 DMA transfers.

Definition at line 101 of file em_dma.h.

Type of DMA transfer.

Enumerator:
dmaCycleCtrlBasic 

Basic DMA cycle.

dmaCycleCtrlAuto 

Auto-request DMA cycle.

dmaCycleCtrlPingPong 

Ping-pong DMA cycle.

dmaCycleCtrlMemScatterGather 

Memory scatter-gather DMA cycle.

dmaCycleCtrlPerScatterGather 

Peripheral scatter-gather DMA cycle.

Definition at line 85 of file em_dma.h.

Amount source/destination address should be incremented for each data transfer.

Enumerator:
dmaDataInc1 

Increment address 1 byte.

dmaDataInc2 

Increment address 2 bytes.

dmaDataInc4 

Increment address 4 bytes.

dmaDataIncNone 

Do not increment address.

Definition at line 66 of file em_dma.h.

Data sizes (in number of bytes) to be read/written by DMA transfer.

Enumerator:
dmaDataSize1 

1 byte DMA transfer size.

dmaDataSize2 

2 byte DMA transfer size.

dmaDataSize4 

4 byte DMA transfer size.

Definition at line 76 of file em_dma.h.


Function Documentation

void DMA_ActivateAuto ( unsigned int  channel,
bool  primary,
void *  dst,
void *  src,
unsigned int  nMinus1 
)

Activate DMA auto-request cycle (used for memory-memory transfers).

Prior to activating the DMA cycle, the channel and descriptor to be used must have been properly configured.

Note:
If using this function on a channel already activated and in use by the DMA controller, the behaviour is undefined.
Parameters:
[in] channel DMA channel to activate DMA cycle for.
[in] primary 
  • true - activate using primary descriptor
  • false - activate using alternate descriptor
[in] dst Address to start location to transfer data to. If NULL, leave setting in descriptor as is from a previous activation.
[in] src Address to start location to transfer data from. If NULL, leave setting in descriptor as is from a previous activation.
[in] nMinus1 Number of DMA transfer elements (minus 1) to transfer (<= 1023). The size of the DMA transfer element (1, 2 or 4 bytes) is configured with DMA_CfgDescr().

Definition at line 392 of file em_dma.c.

References dmaCycleCtrlAuto.

void DMA_ActivateBasic ( unsigned int  channel,
bool  primary,
bool  useBurst,
void *  dst,
void *  src,
unsigned int  nMinus1 
)

Activate DMA basic cycle (used for memory-peripheral transfers).

Prior to activating the DMA cycle, the channel and descriptor to be used must have been properly configured.

Note:
If using this function on a channel already activated and in use by the DMA controller, the behaviour is undefined.
Parameters:
[in] channel DMA channel to activate DMA cycle for.
[in] primary 
  • true - activate using primary descriptor
  • false - activate using alternate descriptor
[in] useBurst The burst feature is only used on peripherals supporting DMA bursts. Bursts must not be used if the total length (as given by nMinus1) is less than the arbitration rate configured for the descriptor. Please refer to the reference manual for further details on burst usage.
[in] dst Address to start location to transfer data to. If NULL, leave setting in descriptor as is from a previous activation.
[in] src Address to start location to transfer data from. If NULL, leave setting in descriptor as is from a previous activation.
[in] nMinus1 Number of DMA transfer elements (minus 1) to transfer (<= 1023). The size of the DMA transfer element (1, 2 or 4 bytes) is configured with DMA_CfgDescr().

Definition at line 455 of file em_dma.c.

References dmaCycleCtrlBasic.

void DMA_ActivatePingPong ( unsigned int  channel,
bool  useBurst,
void *  primDst,
void *  primSrc,
unsigned int  primNMinus1,
void *  altDst,
void *  altSrc,
unsigned int  altNMinus1 
)

Activate DMA ping-pong cycle (used for memory-peripheral transfers).

Prior to activating the DMA cycle, the channel and both descriptors must have been properly configured. The primary descriptor is always the first descriptor to be used by the DMA controller.

Note:
If using this function on a channel already activated and in use by the DMA controller, the behaviour is undefined.
Parameters:
[in] channel DMA channel to activate DMA cycle for.
[in] useBurst The burst feature is only used on peripherals supporting DMA bursts. Bursts must not be used if the total length (as given by nMinus1) is less than the arbitration rate configured for the descriptors. Please refer to the reference manual for further details on burst usage. Notice that this setting is used for both the primary and alternate descriptors.
[in] primDst Address to start location to transfer data to, for primary descriptor. If NULL, leave setting in descriptor as is from a previous activation.
[in] primSrc Address to start location to transfer data from, for primary descriptor. If NULL, leave setting in descriptor as is from a previous activation.
[in] primNMinus1 Number of DMA transfer elements (minus 1) to transfer (<= 1023), for primary descriptor. The size of the DMA transfer element (1, 2 or 4 bytes) is configured with DMA_CfgDescr().
[in] altDst Address to start location to transfer data to, for alternate descriptor. If NULL, leave setting in descriptor as is from a previous activation.
[in] altSrc Address to start location to transfer data from, for alternate descriptor. If NULL, leave setting in descriptor as is from a previous activation.
[in] altNMinus1 Number of DMA transfer elements (minus 1) to transfer (<= 1023), for alternate descriptor. The size of the DMA transfer element (1, 2 or 4 bytes) is configured with DMA_CfgDescr().

Definition at line 527 of file em_dma.c.

References dmaCycleCtrlPingPong.

void DMA_ActivateScatterGather ( unsigned int  channel,
bool  useBurst,
DMA_DESCRIPTOR_TypeDef *  altDescr,
unsigned int  count 
)

Activate DMA scatter-gather cycle (used for either memory-peripheral or memory-memory transfers).

Prior to activating the DMA cycle, the array with alternate descriptors must have been properly configured. This function can be reused without reconfiguring the alternate descriptors, as long as count is the same.

Note:
If using this function on a channel already activated and in use by the DMA controller, the behaviour is undefined.
Parameters:
[in] channel DMA channel to activate DMA cycle for.
[in] useBurst The burst feature is only used on peripherals supporting DMA bursts (and thus this parameter is ignored for memory scatter-gather cycles). This parameter determines if bursts should be enabled during DMA transfers using the alternate descriptors. Bursts must not be used if the total length (as given by nMinus1 for the alternate descriptor) is less than the arbitration rate configured for the descriptor. Please refer to the reference manual for further details on burst usage.
[in,out] altDescr Pointer to start of array with prepared alternate descriptors. The last descriptor will have its cycle control type reprogrammed to basic type.
[in] count Number of alternate descriptors in altDescr array. Maximum number of alternate descriptors is 256.

Definition at line 597 of file em_dma.c.

References dmaArbitrate4, dmaCycleCtrlAuto, dmaCycleCtrlBasic, dmaCycleCtrlMemScatterGather, dmaCycleCtrlPerScatterGather, dmaDataInc4, dmaDataSize4, and DMA_CB_TypeDef::primary.

void DMA_CfgChannel ( unsigned int  channel,
DMA_CfgChannel_TypeDef cfg 
)

Configure a DMA channel.

Configure miscellaneous issues for a DMA channel. This function is typically used once to setup a channel for a certain type of use.

Note:
If using this function on a channel already in use by the DMA controller, the behaviour is undefined.
Parameters:
[in] channel DMA channel to configure.
[in] cfg Configuration to use.

Definition at line 706 of file em_dma.c.

References BITBAND_Peripheral(), DMA_CfgChannel_TypeDef::cb, DMA_CfgChannel_TypeDef::enableInt, DMA_CfgChannel_TypeDef::highPri, and DMA_CfgChannel_TypeDef::select.

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void DMA_CfgDescr ( unsigned int  channel,
bool  primary,
DMA_CfgDescr_TypeDef cfg 
)

Configure DMA descriptor for auto-request, basic or ping-pong DMA cycles.

This function is used for configuration of a descriptor for the following DMA cycle types:

  • auto-request - used for memory/memory transfer
  • basic - used for a peripheral/memory transfer
  • ping-pong - used for a ping-pong based peripheral/memory transfer style providing time to refresh one descriptor while the other is in use.

The DMA cycle is not activated, please see DMA_ActivateAuto(), DMA_ActivateBasic() or DMA_ActivatePingPong() to activate the DMA cycle. In many cases, the configuration only has to be done once, and all subsequent cycles may be activated with the activate function.

For ping-pong DMA cycles, this function must be used both on the primary and the alternate descriptor prior to activating the DMA cycle.

Notice that the DMA channel must also be configured, see DMA_CfgChannel().

Note:
If using this function on a descriptor already activated and in use by the DMA controller, the behaviour is undefined.
Parameters:
[in] channel DMA channel to configure for.
[in] primary 
  • true - configure primary descriptor
  • false - configure alternate descriptor
[in] cfg Configuration to use.

Definition at line 781 of file em_dma.c.

References DMA_CfgDescr_TypeDef::arbRate, DMA_CfgDescr_TypeDef::dstInc, DMA_CfgDescr_TypeDef::hprot, DMA_CfgDescr_TypeDef::size, and DMA_CfgDescr_TypeDef::srcInc.

void DMA_CfgDescrScatterGather ( DMA_DESCRIPTOR_TypeDef *  descr,
unsigned int  indx,
DMA_CfgDescrSGAlt_TypeDef cfg 
)

Configure an alternate DMA descriptor for use with scatter-gather DMA cycles.

In scatter-gather mode, the alternate descriptors are located in one contiguous memory area. Each of the alternate descriptor must be fully configured prior to starting the scatter-gather DMA cycle.

The DMA cycle is not activated by this function, please see DMA_ActivateScatterGather() to activate the DMA cycle. In some cases, the alternate configuration only has to be done once, and all subsequent transfers may be activated with the activate function.

Notice that the DMA channel must also be configured, see DMA_CfgChannel().

Parameters:
[in] descr Points to start of memory area holding the alternate descriptors.
[in] indx Alternate descriptor index number to configure (numbered from 0).
[in] cfg Configuration to use.

Definition at line 904 of file em_dma.c.

References DMA_CfgDescrSGAlt_TypeDef::arbRate, dmaCycleCtrlMemScatterGather, dmaCycleCtrlPerScatterGather, dmaDataIncNone, DMA_CfgDescrSGAlt_TypeDef::dst, DMA_CfgDescrSGAlt_TypeDef::dstInc, DMA_CfgDescrSGAlt_TypeDef::hprot, DMA_CfgDescrSGAlt_TypeDef::nMinus1, DMA_CfgDescrSGAlt_TypeDef::peripheral, DMA_CfgDescrSGAlt_TypeDef::size, DMA_CfgDescrSGAlt_TypeDef::src, and DMA_CfgDescrSGAlt_TypeDef::srcInc.

void DMA_ChannelEnable ( unsigned int  channel,
bool  enable 
)

Enable or disable a DMA channel.

Use this function to explicitly enable or disable a DMA channel. A DMA channel is automatically disabled when the DMA controller has finished a transaction.

Parameters:
[in] channel DMA channel to enable or disable.
[in] enable If 'true' the channel will be enabled. If 'false' the channel will be disabled.

Definition at line 979 of file em_dma.c.

bool DMA_ChannelEnabled ( unsigned int  channel  ) 

Check if DMA channel is enabled.

The DMA channel is disabled when the DMA controller has finished a DMA cycle.

Parameters:
[in] channel DMA channel to check.
Returns:
true if channel is enabled, false if not.

Definition at line 1008 of file em_dma.c.

void DMA_Init ( DMA_Init_TypeDef init  ) 

Initializes DMA controller.

This function will reset and prepare the DMA controller for use. Although it may be used several times, it is normally only used during system init. If reused during normal operation, notice that any ongoing DMA transfers will be aborted. When completed, the DMA controller is in an enabled state.

Note:
Must be invoked before using the DMA controller.
Parameters:
[in] init Pointer to a structure containing DMA init information.

Definition at line 1033 of file em_dma.c.

References CMU_ClockEnable(), cmuClock_DMA, DMA_Init_TypeDef::controlBlock, DMA_Reset(), and DMA_Init_TypeDef::hprot.

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void DMA_IRQHandler ( void   ) 

Interrupt handler for DMA cycle completion handling.

Clears any pending flags and calls registered callback (if any).

If using the default interrupt vector table setup provided, this function is automatically placed in the IRQ table due to weak linking. If taking control over the interrupt vector table in some other way, this interrupt handler must be installed in order to be able to support callback actions.

In order for the user to implement a custom IRQ handler or run without a DMA IRQ handler, the user can define EXCLUDE_DEFAULT_DMA_IRQ_HANDLER with a #define statement or with the compiler option -D.

Definition at line 285 of file em_dma.c.

References DMA_CB_TypeDef::cbFunc, DMA_CB_TypeDef::primary, and DMA_CB_TypeDef::userPtr.

void DMA_RefreshPingPong ( unsigned int  channel,
bool  primary,
bool  useBurst,
void *  dst,
void *  src,
unsigned int  nMinus1,
bool  stop 
)

Refresh a descriptor used in a DMA ping-pong cycle.

During a ping-pong DMA cycle, the DMA controller automatically alternates between primary and alternate descriptors, when completing use of a descriptor. While the other descriptor is in use by the DMA controller, the SW should refresh the completed descriptor. This is typically done from the callback defined for the ping-pong cycle.

Parameters:
[in] channel DMA channel to refresh ping-pong descriptor for.
[in] primary 
  • true - refresh primary descriptor
  • false - refresh alternate descriptor
[in] useBurst The burst feature is only used on peripherals supporting DMA bursts. Bursts must not be used if the total length (as given by nMinus1) is less than the arbitration rate configured for the descriptor. Please refer to the reference manual for further details on burst usage.
[in] dst Address to start location to transfer data to. If NULL, leave setting in descriptor as is.
[in] src Address to start location to transfer data from. If NULL, leave setting in descriptor as is.
[in] nMinus1 Number of DMA transfer elements (minus 1) to transfer (<= 1023). The size of the DMA transfer element (1, 2 or 4 bytes) is configured with DMA_CfgDescr().
[in] stop Indicate that the DMA ping-pong cycle shall stop after completing use of this descriptor.

Definition at line 1110 of file em_dma.c.

References dmaCycleCtrlBasic, and dmaCycleCtrlPingPong.

void DMA_Reset ( void   ) 

Reset the DMA controller.

This functions will disable the DMA controller and set it to a reset state.

Note:
Notice that any ongoing transfers will be aborted.

Definition at line 1202 of file em_dma.c.

Referenced by DMA_Init().

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