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 Slow usb response 
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Joined: Sun Oct 04, 2015 4:06 pm
Posts: 21
Post Slow usb response
Hi All

I am using Fitlet-i with Libusb-1.0 to do Control Transfers to a usb port that has an Industrial I/O board connected to it.

When doing this on my Laptop it takes 185 micro seconds to do a write to the board.
When doing this on The Fitlet-i it takes 700 micro seconds.
Although the Laptop is an Acer Aspire i5 1.6Ghz, I don't believe the speed of the Laptop should make that much difference.
It is the same software running on both, and using either usb 2 or usb 3 makes no difference. The only thing noticeable is that the square pulse varies significantly in width.
By doing a Write to set an output, and then immediately another Write to turn it Off results in a 700 micro second pulse on the Fitlet-i and 185 micro second pulse on my laptop.

Does anyone have any ideas.

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Wed Feb 28, 2018 2:47 am
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Joined: Mon Dec 25, 2017 4:21 pm
Posts: 384
Post Re: Slow usb response
The structure of a USB host controllers is different in Intel and AMD platform. Especially if the device is USB1 (slow old device like mouse / keyboard etc).
If you would like to compare USB behavior, you should compare it with another AMD platform with all-in-one CPU, in which the USB controller is on the same silicon.

I wouldn't worry about the delays of several milliseconds in your case, it is normal behavior.


Thu Mar 01, 2018 5:01 pm
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Joined: Sun Oct 04, 2015 4:06 pm
Posts: 21
Post Re: Slow usb response
Hi All

Thanks for your response.
Am I likely to get the same degraded performance if I change to Ethernet GPIO ?

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Thu Mar 01, 2018 6:31 pm
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Joined: Tue Mar 13, 2018 4:23 am
Posts: 2
Post Re: Slow usb response
They have different structure.


Tue Mar 13, 2018 4:24 am
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