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Maximum USB 3.0 speed using USBBulkLoopAuto example | Cypress Semiconductor

Maximum USB 3.0 speed using USBBulkLoopAuto example

Summary: 2 Replies, Latest post by RSKV on 06 Dec 2012 03:08 AM PST
Verified Answers: 0
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Kavya's picture
11 posts


I am trying to find the maximum speed of transfer over the USB 3.0 to FX3 board using the USBBulkLoopAuto example.

I changed the max. no. of packets to 0x08 in the cyfxbulklpdscr.c file in the bulkloopauto example and used a USB traffic analyser called USBlyzer. And if what I understood is correct it gave me a speed of 40MBps.

I am using atmels AT24C1024B I2C EEPROM. However when I try to increase the data I send to more 8-9KB I am getting the error code: 997. Also when  try to change the size of each packet to 2048 bytes the device manager gives an error message saying "this device cannot start (code 10). What isthe problem here? Is there a better way to findthe max speed of transfer usingthe bulk loopauto exampel specifically? or using the FX3 board as such?

Thanks & Regards,


Lumpi6's picture
341 posts


the usb packet size should be 1024 for SS, 512 for HS and others 64 bytes in bulk transfers. You may increase if you use bursts 16 (is max). Have you a specifically reason to try it with the bulk loop auto example? I am not sure if these example is optimezed to check traffic throughput. You may check it with the streamer app and the UsbBulkSourceSink example.



rskv's picture
Cypress Employee
1134 posts

Hi Kavya,

Yes. As Lumpi already told you, use UsbBulkSourceSink and streamer application to measure the throughput of Bulk transfers. And go for UsbIsoSourceSink example if you want to measure throughtput of ISO transfers.

We have seen more than 400MBps with bulk transfers.


sai krishna.

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