The SD card can not access by 4-bit mode on OMAPL137/TMS320c6747

tong sun1

Other Parts Discussed in Thread: TMS320C6747

I use the OMAPL137/TMS320c6747's SD controller to develop the SD card. And refer the spectrumdigital commpany's SD example.

The problem is when I use 4-bit mode to transfer the data,It can only successful with the data 0-0x0e.if the data bigger,it can not set the flag bit in MMCST0 or occur read error.While,the write operation is pretty good.

When I use 1-bit mode, the read and write operation both work very well.

It's so strange,Hope someone give me some addvice, Thank you!

over 11 years ago

0 Brad Griffis over 11 years ago

TI__Guru*** 125430 points

This is a bit of a shot in the dark, but I've seen a number of SD card issues over the years that ultimately came down to ringing on the clock pin causing sampling issues. In general a 22-33 ohm series resistor on the clock line has typically resolved the issues. Just a guess...

0 tong sun1 over 11 years ago in reply to Brad Griffis

Prodigy 120 points

Thanks a lot for your timely reply!

I've tried series registers from 18 ohm,24ohm,...to 220ohm on the clock line.But it still has the problem.In addition,I use Micro SD card of Sandisk.

0 Brad Griffis over 11 years ago in reply to tong sun1

TI__Guru*** 125430 points

Does slowing the clock speed make it work? Might want to check your power supplies and decoupling caps again.

0 tong sun1 over 11 years ago in reply to Brad Griffis

Prodigy 120 points

Thank you for your useful advice!

Just as you said,I check the hardware system. I find the wire I use to connect the board and SD Card slot is too long.I

change and it works!

Thanks!

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The SD card can not access by 4-bit mode on OMAPL137/TMS320c6747