Re: [Gumstix-users] How to mesure current SPI transfer speed

[Kevyn-Alexandre P. <ka...@ro...>]

On Sat, 2011-01-08 at 11:16 +0900, Jassi Brar wrote:
> On Sat, Jan 8, 2011 at 3:51 AM, Kevyn-Alexandre Paré
> <ka...@ro...> wrote:
> > Hi,
> >
> > What's the best way to calculate the current SPI transfer speed?
> >
> > Right now I use something like that and transfer one spi_message with 1
> > spi_transfer of 100000 bytes and I do the math... I know that this is
> > not accurate and was wondering if anyone have a better way?
> >
> >
> > struct timeval tv_before;
> > struct timeval tv_after;
> >
> > do_gettimeofday(&tv_before);
> >    status = spi_sync(spike_dev.spi_device, &spike_ctl.msg);
> > do_gettimeofday(&tv_after);
> >    long elapsedTime = (tv_after.tv_usec - tv_before.tv_usec);
> 
> Transfer speed is tightly linked to MOSI/MISO bit rates.
> But the overall throughput would depend on the protocol that
> you run over SPI.

Effectively, but how to monitor that I respect, for example, a
requirement of 5Mbps with a chip... I'm already sending data at

#define SPI_BUS_SPEED 5000000
spi_device->max_speed_hz = SPI_BUS_SPEED;

So does this settings ensure it to always be at 5Mhz?

I will try to test it by settings it to higher speed to see what happen
ex: 48000000 (48Mhz)

Regards,

--
Kevyn-Alexandre Pare