SAM High speed USB - how fast is it, really?

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Hi everyone,

I would just like to know if anyone ever measured how fast the High Speed USB interface of the newer SAM devices is. I would like to achieve about 10 MByte/s bulk data transfer and I need to choose a MCU for that.
A proof of concept device is already working, but the TI Tiva C series MCUs only have a full speed PHY integrated, so only about 500kByte/s is possible with that.

Thanks in advance,

Patrick

"Some people die at 25 and aren't buried until 75." -Benjamin Franklin

 

What is life's greatest illusion?"  "Innocence, my brother." -Skyrim

 

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For future reference, if anyone ever has the same question and stumbles over this:

The SAM E70 is VERY fast, we measured peak transfer rates of up to 40 MByte/s not including protocol overhead, which is close to the theoretical limit. The device never NACKs on any transfer.

We used the ASF vendor device example as a base for our application, it's quite good.

There are only two little issues with the ASF: In the default conf_usb.h, there is the following passage. Obviously, the SAME70 is missing in that "if(..)", so you must add it yourself. Otherwise the device will operate only in full speed mode. In that mode, about 1 MByte/s is achievable. The second issue is that it doesn't work with the caches enabled, we have not yet figured out why.

/**
 * Device speeds support
 * Low speed not supported by this vendor class
 * @{
 */
//! To authorize the High speed
#if (UC3A3||UC3A4)
# define  USB_DEVICE_HS_SUPPORT
#endif

-Patrick

"Some people die at 25 and aren't buried until 75." -Benjamin Franklin

 

What is life's greatest illusion?"  "Innocence, my brother." -Skyrim

 

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What version of ASF are you using?  I had problems getting high speed mode working reliably on a SAME70 with ASF4/START due to a buggy driver (480Mbps).  Full speed mode works reliably though (12Mbps).  I seriously considered downgrading to ASF3 for the high speed USB driver but gave up as my app's performance was limited elsewhere.  I'm just curious if you were able to get high speed mode working with ASF4 and SAME70?

 

 

Last Edited: Wed. May 9, 2018 - 02:30 PM
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ScottMN wrote:
What version of ASF are you using?

 

We used ASF 3.35.1.

"Some people die at 25 and aren't buried until 75." -Benjamin Franklin

 

What is life's greatest illusion?"  "Innocence, my brother." -Skyrim