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USB low-full-high speed peripherals Forum Discussions

wetechautomatio
Level 1
Level 1
First question asked Welcome!

We are developing an example where device continuously stream data through an isochronous IN endpoint. Now my question was as interrupt and isochronous have lot of similarities :

  1. Max 1024 packets in USB HS
  2. both are for bandwidth guarantee.
  3. Host can poll device every micro frame.

can I use my host interrupt endpoint to configure is to read from device's isochronous endpoints ?

device isochronous endpoints is following :

===>Endpoint Descriptor<===
bLength: 0x07
bDescriptorType: 0x05
bEndpointAddress: 0x81 -> Direction: IN - EndpointID: 1
bmAttributes: 0x05 -> Isochronous Transfer Type, Synchronization Type = Asynchronous, Usage Type = Data Endpoint
wMaxPacketSize: 0x0180 = 1 transactions per microframe, 0x180 max bytes
bInterval: 0x01

I understand there is NACK/ACK token in the interrupt endpoints , but let say if device ignores this NACK/ACK token can I still communicate with device using my interrupt endpoints ?

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1 Solution
PranavaYN
Moderator
Moderator
Moderator
500 replies posted 250 solutions authored 50 likes received

Hi,

 

Even though Isochronous and Interrupt endpoints have many similarities, they are defined separately in USB spec.  Therefore it is not recommended to use different types of endpoints on Host and Device side.

May I know the exact reason as to why you would want to do so?

Best regards,
Pranava

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3 Replies
PranavaYN
Moderator
Moderator
Moderator
500 replies posted 250 solutions authored 50 likes received

Hi,

 

Even though Isochronous and Interrupt endpoints have many similarities, they are defined separately in USB spec.  Therefore it is not recommended to use different types of endpoints on Host and Device side.

May I know the exact reason as to why you would want to do so?

Best regards,
Pranava
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wetechautoma
Level 1
Level 1
First reply posted Welcome!

Hi Pranava,

We are trying to publish a research paper for this. Do you think it can be possible ?

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PranavaYN
Moderator
Moderator
Moderator
500 replies posted 250 solutions authored 50 likes received

Hi,

I have never come across such operation before. As it is not defined by the spec, I can not guarantee it's working as there are multiple factors such as Drivers, OSes and devices involved.

Best regards,
Pranava
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