Lpc2000

On Sun, Nov 27, 2005 at 12:40:14PM +0100, Bertrik Sikken wrote:
> Have you tried the pre-erase or do you get this from a datasheet?

I have implemented it. It makes a small, but measurable difference on writing
sequences of blocks.

> You snipped the part where I said I measured the time it took to read
> and write *4MB* of contiguous raw data directly onto the disk (without a

Sorry, I misread your original post. 

> My speeds come out at roughly 300 kB/s.

So that could be accounted for by a slow card, though the only card I have
tried that is noticeably slower than the 600KB/s I mentioned is an old 32MB
card, and it is slower only for writing, not reading.

In my case the speed is also constrained by streaming the data via full-speed
USB, which has a theoretical upper limit of about 1 MB/s. But in general reading
an SD card should be limited only by the SPI bit rate, so even at your 7.5MHz, it
should be possible to read at closer to 900 than 300 KB/s, so I still suspect some
less than optimal coding might be contributing to your results.

Careful attention to the SPI code was required in my application to achieve
the results that I did (all written in C though, no assembly code).

Clyde