TUSB4020BI: Maximum Packet Size

Eric Din71

Part Number: TUSB4020BI

I am working with a F28379D control card to develop a data acquisition platform that will stream data to a computer. I am achieving 6Mbps+ throughput to the PC right now with the USB 2.0 Full Speed based on some recommendations from folks on this site to change the maximum allowable bulk out packet (increased to 1024 bytes).

I am intending to have multiple boards running at once while maintaining the same throughput per board, so I am hoping to use a USB hub to bump the speed at the PC to the high-speed 480Mbps. However, I have been limited with the current Cypress hub development board I have as it seems it only accepts 64-byte packets (datasheet also says 64 byte RAM), so I lose a lot of my throughput when I connect the control card through the hub.

Does the TUSB4020BI allow for packet length up to 1024 bytes?

over 6 years ago

0 Malik Barton57 over 6 years ago

TI__Guru 64326 points

Does the F28379D control card support High speed or Full speed functionality per the USB 2.0 spec? Could you provide a block diagram of your design to verify the use case of the TUSB4020BI?

TUSB4020BI does support High Speed functionality with a maximum packet size of 1024 bytes.

0 Eric Din71 over 6 years ago in reply to Malik Barton57

Prodigy 230 points

Hi Malik,

The F2837xD MCUs support Full Speed USB 2.0 at 12 Mbps. See below for block diagram. I am only using one of the downstream ports hoping that this will be functionally equivalent to the F2837xD having USB 2.0 High Speed capabilities.

Thanks

0 Malik Barton57 over 6 years ago in reply to Eric Din71

TI__Guru 64326 points

Good Morning Eric,

TUSB4020BI will not repackage the data from the F2837xD, therefore all data will remain as a 64 byte package. TUSB4020BI will operate at USB 2.0 HS and send the packages to the USB hub at 480 Mbps.

0 Eric Din71 over 6 years ago in reply to Malik Barton57

Prodigy 230 points

Hi Malik,

Thanks for the response. I have changed the header files to send 1024-byte packets from the F2837xD, so I am hoping that the TUSB4020BI will forward on those 1024-byte packets at the USB 2.0 HS. I have the development board coming in today and will verify.

Thanks,
Eric

0 Malik Barton57 over 6 years ago in reply to Eric Din71

TI__Guru 64326 points

Eric,

USB Full Speed allows for 64 byte packets maximum, so if the F2837xD is only USB Full Speed capable then sending 1024 byte packets may result in unexpected errors.

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TUSB4020BI: Maximum Packet Size