USB_ADC Data transfer problem

[sumy]

Hi ,

I am using K70 & Mqx3.8.And I am writing an application for transferring data from ADC to USB hard disk.For that 1st I built "Freescale MQX 3.8\usb\host\build\cw10\usb_hdk_twrk70f120m"
then I built "Freescale MQX 3.8\mfs\examples\mfs_usb\cw10\mfs_usb_twrk70f120m" and modified in this example.

And for my application ,it should be transferred @512kbytes/sec but
it is being transferred @

            10 seconds when buffer size = 50kb

            14 seconds when buffer size = 100k b

            41 seconds when buffer size = 510k

            78 seconds when buffer size = 1024k

            135 seconds when buffer size = 2048k
            
            33 minutes when buffer size = (1024*8)k


And one more thing is that when I transferred the data of 455 Mb from my system to that Usb hard disk then it took only 75 seconds(6.06 Mb/sec).

So ,Please Can any one tell me that what is the Issue ?And where I should I modified ? Please Reply ASAP.

Thank You

[JuroV]

I see  that you want to send 512kB / sec = 4Mbit / sec = cca 4 Msamples/ sec.

This is at the edge of ADC transfer and such ADC sample rate could be achieved only without external HW triggering, but in a conversions that are solely requested in the polled mode.

In such case I suppose that the PDB period is very short and huge amount of interrupts are generated, that downgrade the performance of the other normal-priority code, for example USB stack for KHCI.

Can you give us some details what was tested, some pieces of code etc?

[sumy]

Hi JuroV,

Here I am attaching one simple "MFS-USB"example which I have taken from standard example with some modifications.I am craeting one file on USB and trying to write in that File but still speed is very slow whatever I have written earlier.

Please You just go through my example and if possible you make it faster as my requirement.

Thank You

Sumy