FX3- change packet size in ISOC module (USBIsocSourceSink)

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mamu_3907446
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Hi,

I would like to change the packet size in the ISOC module (USBIsocSourceSink)

in the 'cyfxisosrcsink.h'  I'm changing 'CY_FX_ISO_MAXPKT' parameter from 1024 to 225.

I'm successfully program the FX3 but the device isn't enumerated.

is there any other parameter I should change in order to change packet size?

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Hello,

Please refer to Section 4.4.8 Isochronous Transfers, more specifically 4.4.8.1. which says about the ISOC endpoint size requirements in USB 3.1 Specification from the following link: https://manuais.iessanclemente.net/images/b/bc/USB_3_1_r1.0.pdf

This section explains about the ISOC endpoint usage and requirements in SS USB.

Regards,
Yashwant

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YashwantK_46
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Hello,

Along with the CY_FX_ISO_MAXPKT set to 225, you will also need to change the CY_FX_ISO_BURST to (1) as shown below:

pastedImage_0.png

This will make the device enumerate properly with an endpoint size of 224.

Regards,
Yashwant

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thanks a lot!

and if I would like to change packet size to 1 byte? is it possible?

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Hello,


Yes, the packet size can be set to 1 Byte as well.

But to only get one packet of 1 Byte, you can set the Mult Setting CY_FX_ISO_PKTS to (1).

Regards,
Yashwant

Great, thanks.

what is the theory behind the correlation  between those different parameters :

1. max packets

2. ISOC packets

3. max burst size

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Hello,

Please refer to Section 4.4.8 Isochronous Transfers, more specifically 4.4.8.1. which says about the ISOC endpoint size requirements in USB 3.1 Specification from the following link: https://manuais.iessanclemente.net/images/b/bc/USB_3_1_r1.0.pdf

This section explains about the ISOC endpoint usage and requirements in SS USB.

Regards,
Yashwant

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