cards for the uSD slot (was Re: Battery and power questions)

Ron K. Jeffries rjeffries at gmail.com
Tue Nov 2 21:22:54 EDT 2010


That's much faster than I expected. Thanks for the data.
---
Ron K. Jeffries






On Tue, Nov 2, 2010 at 13:28, Werner Almesberger <werner at openmoko.org>wrote:

> Ron K. Jeffries wrote:
> > Roughly what speed in bits per second would you estimate
> > a microsd/spi interface from Ben can achieve?
>
> Just tested it. I got 2.4 Mbps, best-case, which is a bit faster than
> I thought I had seen in earlier experiments. The code in question
> looks like this:
>
>
> static void snd(uint16_t v)
> {
>        int i;
>
>        for (i = 0; i != 16; i++) {
>                if ((v >> i) & 1)
>                        PDDATS = X;
>                else
>                        PDDATC = X;
>                PDDATS = Y;
>                PDDATC = Y;
>        }
> }
>
> ...
>
>        while (1)
>                snd(0x555f);
>
>
> Here's a picture to prove it:
>
> http://downloads.qi-hardware.com/people/werner/tmp/usdbb.png
>
> There is a fair amount of background activity, which "steals" cycles,
> so continuous data transmission without suppressing other system
> activity may only be about half as fast.
>
> - Werner
>
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