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

[TDK]

The PC side needs to poll quickly enough. Most programs do not do this. What are you using on the PC side? Eliminate hubs from the chain. Ensure you send a new buffer immediately after the previous buffer is sent.