slow data rate with usb cdc on nucleo-h533

[MScha.8]

Hi All,

I'm building an instrument that needs to stream data to a PC at ~4Mbps. People were claiming nearly twice this with USB CDC so I chose the nucleo-h533 board and started with the Ux_Device_CDC_ACM example. I disconnected the USART code and added a loop that calls ux_device_class_cdc_acm_write and then I measure the rate at which I receive data on the PC. I can't get past ~1.8Mbps.

I have tried the following:

• varying the size of the buffer passed in from 64 to 2048
• enabling ZERO copy in the driver UX_DEVICE_ENDPOINT_BUFFER_OWNER=1 and defining UX_DEVICE_CLASS_CDC_ACM_ZERO_COPY
• setting USBD_CDCACM_EPINCMD_FS_BINTERVAL to 1 instead of 5

In all cases, the baud rate remains about the same at 1.8Mbps. Is there anything I can do to improve this?

Best,

Marc

[MScha.8]

I get 16kB max reads and 7Mbps on my laptop.

It turns out I can get up to 8Mbps from my desktop depending on which USB plugs I use so it is a PC h/w issue.

Thanks so much for your help.

-Marc

[TDK]

Thanks for reporting back with results.

That's interesting that one device seems to limit the max readout or buffer size to 4 kB.

Makes me wonder if the bug reported in that other thread could be due to the hardware and not something within Windows. Now I want to create an STM32 project with a USB CDC ACM host and see (a) the max throughput and (b) if packets are ever dropped.