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USB CDC ACM max transfer speed

Hiihtaja

Hello !

I'm using  USB CDC ACM serial port in interrupt driven mode.

I can see driver operate by 64 bytes chunks.

Linux PC is used as data source and I can see 450KB/s in case of RX and about 250KB/S in case of TX.

Does those digits are good enough for nRF52840 ?

Can it be faster and generate less interrupts e.g not every 64 bytes ?

Or this is some fundamental constant #define NRFX_USBD_EPSIZE 64 e.g max packet size  for full speed USB and basically everything already fast enough ?

Regards,

Eugene

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  • +1

    Hi,

    Those numbers seem to be in line with what we have found. In our testing we have found the CDC example to yield approximately 215kB/s transfer speed on Windows, and over 300kB/s on Linux. 

    Or this is some fundamental constant #define NRFX_USBD_EPSIZE 64 e.g max packet size  for full speed USB and basically everything already fast enough ?

    Correct, 64 is the max for USB Full speed device.

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  • +1

    Hi,

    Those numbers seem to be in line with what we have found. In our testing we have found the CDC example to yield approximately 215kB/s transfer speed on Windows, and over 300kB/s on Linux. 

    Or this is some fundamental constant #define NRFX_USBD_EPSIZE 64 e.g max packet size  for full speed USB and basically everything already fast enough ?

    Correct, 64 is the max for USB Full speed device.

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