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RB5 Slow USB3 performance
jay.yeh
Join Date: 16 Aug 22
Posts: 1
Posted: Tue, 2022-08-16 20:47
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Hi,

I am using RB5 with LU image(Ubuntu) and libusb to communicate with my own USB device.

The read/write performance is quite slow. Please refer to the following USB analyzer recording:

https://i.imgur.com/gn4sz9b.png

Compared with the result using Raspberry Pi:

https://i.imgur.com/r3zAf8f.png

As shown in the figures above, both the bulk-in/out performance take more than double  time Raspberry pi needed.

After some closer look, the issue seems not in the USB transfer itself. Because most of the time the bus is in the idle mode.

Take the Bulk in 4 byte for example, the time difference between the next 200k byte is 1.459ms in RB5, but the actual transfer takes only 10.8us(similar to Raspberry Pi) and the rest of time the bus is in idle. 

https://i.imgur.com/p9XzCI5.png

If I use the Async version libusb API, the performance would be improved a little bit, but still slower than the Raspberry Pi.

But on Raspberry Pi, the Sync and Async version libusb API has the same performance.

Could anyone help on this issue?

 

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