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USB Superspeed Peripherals

juhu_4653696
New Contributor

hi,

Last time i issue a problem is :

https://community.cypress.com/t5/USB-Superspeed-Peripherals/ubuntu-host-cypress-Isochronous-mode-can...

but it closed, so i create a new question for continue debug.

Since i set:

 FX3_EP_ISO_VIDEO_SS_BURST 0x07
 FX3_EP_ISO_VIDEO_SS_MULT   0x01
 FX3_UVC_ISO_PAYLOAD_SIZE = ((FX3_EP_ISO_VIDEO_SS_BURST + 1) * (FX3_EP_ISO_VIDEO_SS_MULT + 1) * 1024) = (0x07+1)(0x01+1)*1024=16k

0x01, /* Servicing interval for data transfers */

It means cypress will report max palyload size is 16k, bandwidth is 16kB/125us *8= 1Gbps. and i capture usb package:

image.png

It is correct. Could  i reduce the bandwith further?

How i reduce the wBytesPerInterval and open camera successfully?

Thanks!

Jun

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1 Solution
Rashi_Vatsa
Moderator
Moderator

Hello Jun,

As mentioned earlier, the problem seems to be due to  the limitations from host controller. 

The video bandwidth for 800*600 @ 10fps can be around 9.1 MBps (considering 2 bytes per pixel)

means 8k and 250us , open 3 cameras successfully!

>> This means that the isochronous endpoint bandwidth is 32.7 MBps for single camera. This can support the video bandwidth and also the host controller is can support 3 cameras with the same bandwidth. In addition to this as the video bandwidth is less than the isochronous endpoint bandwidth i.e. the reason we do not see CyU3PDmaMultiChannelCommitBuffer Fail status = 71. When the USB host doesn't consume the data in the DMA buffers (filled by the sensor) of FX3, there can be DMA overflow condition which leads to CyU3PDmaMultiChannelCommitBuffer failure

means 8k and 125us, open 3 cameras will "show no space left"

>> This means that the isochronous endpoint bandwidth is 65.5 MBps for single camera

When the bandwidth is reduced the host controller supports 3 cameras but for streaming 1200*1200 more bandwidth will be required and it seems that the USB host controller is not able to allot the bandwidth for 3  camera

Regards,
Rashi

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