[nRF52840] USB CDC baud rate

RE: [nRF52840] USB CDC baud rate

Hieu — Fri, 23 Aug 2024 12:11:43 GMT

Hi Yaxit,

Yes, the CDC example implements echo purely on CDC ACM.
It does use UART, but only for logging.

RE: [nRF52840] USB CDC baud rate

Yaxit — Fri, 23 Aug 2024 07:07:48 GMT

Hi, sorry to resuscitate this old topic. The zephyr's CDC example relies purely on the CDC? In other words, does that classify as "processing data locally"? Or what is meant by that?

RE: [nRF52840] USB CDC baud rate

ovrebekk — Fri, 18 Mar 2022 17:06:52 GMT

[quote user="austin"]1、No matter how much baud rate is set, will it not affect the data transmission rate?[/quote]

No, the USB interface has its own transfer speed limitations which are not linked to the UART baudrate.

If you set up the nRF52 like an FTDI device, and relay the CDC data to a physical UART interface, then you would typically change the baudrate on the UART interface based on the baud rate setting sent over CDC. In this case the throughput would be affected by the baudrate you set, but when you only process the CDC data locally in the nRF device without sending it onto the UART bus then this is not the case.

[quote user="austin"]2、I want to use USB CDC to transmit a large amount of data. What is the maximum transmission rate?[/quote]

We did some tests on this earlier, and found that the host OS affected the maximum transmission rate. You will find the results below:

CDC ACM binary file transfer (Windows): 215 kB/s (1720 kbit/s)

CDC ACM binary file transfer (Linux): 323 kB/s (2584 kbit/s)

Best regards
Torbjørn

RE: [nRF52840] USB CDC baud rate

austin — Fri, 18 Mar 2022 00:42:50 GMT

1、No matter how much baud rate is set, will it not affect the data transmission rate?
2、I want to use USB CDC to transmit a large amount of data. What is the maximum transmission rate?

RE: [nRF52840] USB CDC baud rate

ovrebekk — Thu, 17 Mar 2022 11:31:46 GMT

Do you mean what the maximum baudrate you can configure is, or the maximum data throughput that you can get?

When using USB CDC the baudrate configuration is just a software setting, and doesn't affect the USB throughput.

Best regards
Torbjørn