Buffer picture data from sd card in SDRAM, or not?

[lpcware]

Content originally posted in LPCWare by Martin84 on Wed Oct 09 14:44:46 MST 2013
Hi,

when interfacing an LCD and using SDRAM as framebuffer, how to store pictures in the embedded system?

I want to use an SD card on which the picture data is stored. What is the most efficient way to read the picture data? Should I first buffer the data over the SD/MMC DMA in SDRAM and then work with this data or is it easier to work directly with this data from SD card?

What is the best way?

Does anybody have some experience and can help me? :-)

Regards,

Martin

[lpcware]

Content originally posted in LPCWare by Martin84 on Fri Oct 25 02:09:45 MST 2013
Hi bavarian,

thanks for your reply :-) Yes, I want to use a file system. So that's the reply I needed. First, the copy job will be initialized in software and then it will be done by DMA :-)

Thanks for your "every friday" support ;-)

Regards,

Martin

[lpcware]

Content originally posted in LPCWare by bavarian on Fri Oct 25 01:57:17 MST 2013
Hello Martin,

to be able to read from an SD card (e.g. a BMP) you need to run a software which is able to handle the file system on the SD card.

A relatively complex example can be found here:  http://www.lpcware.com/system/files/lpcopen_1_03a_4370_lpcxpresso_lpclink2.zip

     .\lpcopen_v1.03\applications\lpc18xx_43xx\examples\periph\periph_sdmmc


An example which reads/write in raw mode can be found here:

     .\lpcopen_v1.03\applications\lpc18xx_43xx\examples\misc\app_sdmmc_meas


The data copy job can of course be done using the DMA feature, the AHB connection of SD/MMC and SDRAM ensures that this is done fast and efficiently.

Regards,
NXP Support

[lpcware]

Content originally posted in LPCWare by Martin84 on Thu Oct 17 05:11:03 MST 2013
Ok THANK YOU :-)

How can I copy the picture data from SD Card to SDRAM? Do I have to do it manually or is there an DMA between SD and SDRAM?

In the picture of AHB-Matrix there is a connection between SD/MMC-Master and EMC-Slave, so I would guess that it is possible to copy the data per DMA.

Can you give me another hint? :-)

Regards,

Martin

[lpcware]

Content originally posted in LPCWare by bavarian on Thu Oct 17 01:24:27 MST 2013
Hello Martin,

you need to have the display buffer in a memory which is in the ARM memory mapped area. The DMA of the LCD controller cannot read from an SD card.

For LPC1800/4300: you could read directly from a qSPI memory, because the SPIFI converts this serial flash into a memory mapped flash. Depending on the display size and color depth the speed of the SPIFI could be sufficient.

In case of the SD card you need to copy the picture data into SDRAM first.

Regards,
NXP Support.