emUSB DMA support for USB Device?

This site uses cookies. By continuing to browse this site, you are agreeing to our Cookie Policy.

  • emUSB DMA support for USB Device?

    Dear Forum,

    I read through the documentation of emUSB Device (UM09001.pdf) but couldn't find a note about using DMA. However, the given performance values in chapter 23.2. it looks impossible for me to gain without DMA. Can anyone point me how and where to link DMA to the emUSB Device library?

    Best Regards
    Markus

  • Whether DMA is used or not depends on the driver (some USB controllers do not even have DMA). Which driver are you using?
    Please read the forum rules before posting.

    Keep in mind, this is *not* a support forum.
    Our engineers will try to answer your questions between their projects if possible but this can be delayed by longer periods of time.
    Should you be entitled to support you can contact us via our support system: segger.com/ticket/
    Or you can contact us via e-mail.

  • Hi Yan,

    thanks for the quick reply.
    At the moment I'm not using any driver. My µC is a Atmel/Microchip SAME70. Currently I use a composite MSD/CDC setup build on the sources that are provided by Microchip. The MSD is connected to the µSD card (4 data lines). I gain about 9MByte/s upload speed. So your published 44.1MByte/s (or is it MBit/s ?) sounds promising to me and worth to migrate to your library.
    I will request an evaluation version of the SAMV7 driver on your website. It should be possible to adapt it to the SAME7. What I found in the datasheet is that they are the same concerning USB.

    Best Regards
    Markus

  • MByte/s is correct, but it is for a different MCU (LPC43 with the EHCI driver (we will add more info to the website on that)).
    On the SAMV7 we do not use DMA as the performance can not be improved by using DMA.
    Out most recent performance measurements on the Atmel ATSAMV7 XPlainedUltra are as follows:
    Read bench (target measurement): 28008 KByte/sec
    Read bench (host measurement): 28054 KByte/sec
    Write bench (target measurement): 40992 KByte/sec
    Write bench (host measurement): 41025 KByte/sec
    Please read the forum rules before posting.

    Keep in mind, this is *not* a support forum.
    Our engineers will try to answer your questions between their projects if possible but this can be delayed by longer periods of time.
    Should you be entitled to support you can contact us via our support system: segger.com/ticket/
    Or you can contact us via e-mail.