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Altera_Forum's avatar
Altera_Forum
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12 years ago

Read from sd card an image on DE2-115

Hello I am writing a pure verilog code reading an image from sd card which i will show on display(vga). Can anyone help me with it i can't find the way to start. Thank you A.A
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Altera_Forum
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12 years ago

The 'best' protocol for speed is to implement the nibble (4-bit) wide interface SD cards support. However, the 'best' protocol for simplicity (probably the one you want) is the standard SPI interface SD cards also support. 3 signals driven into the SD card (clock, data in and chip select) and one return signal (data out). All transactions are byte (8-bit) based.

The following link takes you to a page with plenty of information on using the SPI protocol with SD cards:

http://elm-chan.org/docs/mmc/mmc_e.html (http://elm-chan.org/docs/mmc/mmc_e.html)

Assuming you run the interface at 25MHz and you store uncompressed data in the SD card, you should be able to read out a standard VGA image in around 30ms. Higher definition images will take proportionally longer.