Example of DMA and SSP

[md1]

Posted on November 09, 2006 at 02:10

Example of DMA and SSP

[kais]

Posted on May 17, 2011 at 09:31

Hi MD,

Please find here attached an STR9 project shows how to make a DMA transfer between SSP0 and memory.

This example aims to send an “SSP0_Buffer_Tx� buffer from memory to SSP0 data register and then to “SSP0_Buffer_Rx� buffer.

If you want to verify the status of the transfer you can see the content of the “SSP0_Buffer_Rx� buffer through the watch tool and make a comparison with the source buffer.

Regards.

Eris.

[md1]

Posted on May 17, 2011 at 09:31

Hi,

Does anyone have a working example of how to a transfer data from memory to SSP using burst mode?

Marty.

[md1]

Posted on May 17, 2011 at 09:31

Hi Eris,

I have another DMA question, and wondered if you could help?

The last DMA sample you sent worked great, but now I need to do something slightly different.

The scenario above is transfering from memory to the DMA.

Now I need to transfer memory from the a peripheral (SSP1) to memory, but keep SSP1 in master mode.

Example: I need to transfer 512 bytes (1 sector) from an MMC card to STR9 memory.

So as I understand it, a single DMA request is issued when the receive FIFO contains at least 1 character. A burst request will be issued when the FIFO contains 4 or more characters.

I assume then I will have to trigger the transfer by sending data. I am trying to do this by sending 8 bytes manually. (Need to send dummy data by using another DMA channel in future..)

Here is my code:

// Setup STR9 SSP1 for MMC card.

SSP_DeInit(SSP1);

SSP_StructInit(&g_ssp);

g_ssp.SSP_FrameFormat = SSP_FrameFormat_Motorola;

g_ssp.SSP_Mode = SSP_Mode_Master;

g_ssp.SSP_CPOL = SSP_CPOL_Low;

g_ssp.SSP_CPHA = SSP_CPHA_1Edge;

g_ssp.SSP_DataSize = SSP_DataSize_8b;

g_ssp.SSP_SlaveOutput = SSP_SlaveOutput_Disable;

g_ssp.SSP_ClockRate = 0xB;

g_ssp.SSP_ClockPrescaler = 12;

SSP_Init(SSP1, &g_ssp);

SSP_DMACmd(SSP1, SSP_DMA_Receive, ENABLE);

SSP_Cmd(SSP1, ENABLE); // Enable the SSP0 peripheral

DMA_SyncConfig(DMA_SSP1_RX_Mask, ENABLE);

DMA_ITConfig(MMC_DMA_CHANNEL, ENABLE);

DMA_ITMaskConfig(MMC_DMA_CHANNEL, DMA_ITMask_ITC, ENABLE);

DMA_StructInit(&g_dma);

g_dma.DMA_Channel_LLstItm = 0;

g_dma.DMA_Channel_SrcAdd = (u32)&SSP1->DR; g_dma.DMA_Channel_DesAdd=0;

g_dma.DMA_Channel_SrcWidth= DMA_SrcWidth_Byte; g_dma.DMA_Channel_DesWidth= DMA_DesWidth_Byte; g_dma.DMA_Channel_FlowCntrl=DMA_FlowCntrl2_DMA; g_dma.DMA_Channel_TrsfSize = 0;

g_dma.DMA_Channel_Src = DMA_SRC_SSP1_RX;

g_dma.DMA_Channel_DesAdd=(u32)buffer;

g_dma.DMA_Channel_TrsfSize = 512;

DMA_ChannelSRCIncConfig (MMC_DMA_CHANNEL, DISABLE);

DMA_ChannelDESIncConfig (MMC_DMA_CHANNEL, ENABLE);

DMA_Init(MMC_DMA_CHANNEL, &g_dma); DMA_ChannelCmd(MMC_DMA_CHANNEL, ENABLE);

Any ideas appreciated..

Martin.

[kais]

Posted on May 17, 2011 at 09:31

Hi MD,

Yes, because we can take advantages of burst mode when the transmit /receive FIFO is enabled, in this case all we have to-do is to specify the burst size in the DMA structure.

Concerning the DMA_SyncConfig (DMA_SSP0_TX_Mask, ENABLE) you have right.

Reagrds

Eris.

[md1]

Posted on May 17, 2011 at 09:31

Hi Eris,

Thanks for that, works a treat. It seems the mistake I was making was calling the DMA_ChannelSRCIncConfig function after DMA_Init.

Does this example take advantage of the burst mode?

Also, does your code contain a slight error in the ''DMA_SyncConfig(SSP_DMA_Transmit, ENABLE);'' function? According to the softlib manual parameter 1 should be DMA_SSP0_TX_Mask? i.e

DMA_SyncConfig(DMA_SSP0_TX_Mask, ENABLE);

Thanks again eris...

[md1]

Posted on May 17, 2011 at 09:31

Hi Yuantu,

In my application, I have used the EFSL filesystem drivers, and implemented SPI drivers using the STR9 libs. I have attached the relevant code.

I am aware I need to re-submit this under the terms of the GNU and I will as sooon as poss.

The GPIO setup is in another file, but if you want that as well then let me know and I will post.

Martin.

[yuantuh]

Posted on May 17, 2011 at 09:31

Hi MD,

I am going to read/write data from/to SD/MMC using 91x_lib through ssp0. Could you please give me a guide how to do that, say writing a sector data into SD/MMC and reading it back.

Thank you.

Yuantu

[md1]

Posted on May 17, 2011 at 09:31

OK...

Sorry, the code I posted works fine. It's just that it needs 512 bytes before a terminal count is issued, and I need to send this data out myself. So to do this job, it looks like I need 2 DMA channels. 1 for receiving the data, and 1 for sending out.

Cheers,

Martin.

[md1]

Posted on May 17, 2011 at 09:31

Hi Yantu,

I have attached a version of main.c containing the initialisation routines.

Martin.

[yuantuh]

Posted on May 17, 2011 at 09:31

Hi Martin,

Could you please send me main.c. I have problems how to read/write SD in the main function. I am using SSP0 and have no interrupt.

Thank you.

Yuantu